Generate strongly-typed C# client for ASP.Net Core Web API with OpenAPI (swagger) support running on localhost

Some time ago I wrote how to generate C# client for web api with OpenAPI support using online service https://generator3.swagger.io/api/generate. Limitation of this approach is that web api should be available online as well. But what to do if you develop web api and it is available only on localhost? One of the way is to use https://github.com/swagger-api/swagger-codegen but it is not very easy to use it on localhost.

Simpler solution is to use tool called NSwagStudio. At first we need to add support of OpenAPI to our web api - in my previous post I wrote how to do that: Add OpenAPI (Swagger) support to ASP.Net Core Web API. We will use the same code example here.

When we add OpenAPI support to our web api in addition to online documentation (which is available by url http://localhost:{port}/swagger/index.html) we also get endpoint with OpenAPI (swagger) JSON:

http://localhost:{port}/swagger/v1/swagger.json

which looks like this:

Having this endpoint it is very easy to generate strongly-typed C# client for our web api running on localhost using mentioned NSwagStudio. All we have to do is to choose runtime (we will use .NET6), paste url of swagger.json endpoint to the studio, check CSharp Client checkbox and click Generate Outputs:

Here is example of C# client generated for web api from our example with default settings:

//----------------------
// <auto-generated>
//     Generated using the NSwag toolchain v13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0)) (http://NSwag.org)
// </auto-generated>
//----------------------

#pragma warning disable 108 // Disable "CS0108 '{derivedDto}.ToJson()' hides inherited member '{dtoBase}.ToJson()'. Use the new keyword if hiding was intended."
#pragma warning disable 114 // Disable "CS0114 '{derivedDto}.RaisePropertyChanged(String)' hides inherited member 'dtoBase.RaisePropertyChanged(String)'. To make the current member override that implementation, add the override keyword. Otherwise add the new keyword."
#pragma warning disable 472 // Disable "CS0472 The result of the expression is always 'false' since a value of type 'Int32' is never equal to 'null' of type 'Int32?'
#pragma warning disable 1573 // Disable "CS1573 Parameter '...' has no matching param tag in the XML comment for ...
#pragma warning disable 1591 // Disable "CS1591 Missing XML comment for publicly visible type or member ..."
#pragma warning disable 8073 // Disable "CS8073 The result of the expression is always 'false' since a value of type 'T' is never equal to 'null' of type 'T?'"
#pragma warning disable 3016 // Disable "CS3016 Arrays as attribute arguments is not CLS-compliant"
#pragma warning disable 8603 // Disable "CS8603 Possible null reference return"

namespace MyNamespace
{
    using System = global::System;

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class Client 
    {
        private string _baseUrl = "";
        private System.Net.Http.HttpClient _httpClient;
        private System.Lazy<Newtonsoft.Json.JsonSerializerSettings> _settings;

        public Client(string baseUrl, System.Net.Http.HttpClient httpClient)
        {
            BaseUrl = baseUrl;
            _httpClient = httpClient;
            _settings = new System.Lazy<Newtonsoft.Json.JsonSerializerSettings>(CreateSerializerSettings);
        }

        private Newtonsoft.Json.JsonSerializerSettings CreateSerializerSettings()
        {
            var settings = new Newtonsoft.Json.JsonSerializerSettings();
            UpdateJsonSerializerSettings(settings);
            return settings;
        }

        public string BaseUrl
        {
            get { return _baseUrl; }
            set { _baseUrl = value; }
        }

        protected Newtonsoft.Json.JsonSerializerSettings JsonSerializerSettings { get { return _settings.Value; } }

        partial void UpdateJsonSerializerSettings(Newtonsoft.Json.JsonSerializerSettings settings);

        partial void PrepareRequest(System.Net.Http.HttpClient client, System.Net.Http.HttpRequestMessage request, string url);
        partial void PrepareRequest(System.Net.Http.HttpClient client, System.Net.Http.HttpRequestMessage request, System.Text.StringBuilder urlBuilder);
        partial void ProcessResponse(System.Net.Http.HttpClient client, System.Net.Http.HttpResponseMessage response);

        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual System.Threading.Tasks.Task<System.Collections.Generic.ICollection<User>> ListAsync()
        {
            return ListAsync(System.Threading.CancellationToken.None);
        }

        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual async System.Threading.Tasks.Task<System.Collections.Generic.ICollection<User>> ListAsync(System.Threading.CancellationToken cancellationToken)
        {
            var urlBuilder_ = new System.Text.StringBuilder();
            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/User/List");

            var client_ = _httpClient;
            var disposeClient_ = false;
            try
            {
                using (var request_ = new System.Net.Http.HttpRequestMessage())
                {
                    request_.Method = new System.Net.Http.HttpMethod("GET");
                    request_.Headers.Accept.Add(System.Net.Http.Headers.MediaTypeWithQualityHeaderValue.Parse("text/plain"));

                    PrepareRequest(client_, request_, urlBuilder_);

                    var url_ = urlBuilder_.ToString();
                    request_.RequestUri = new System.Uri(url_, System.UriKind.RelativeOrAbsolute);

                    PrepareRequest(client_, request_, url_);

                    var response_ = await client_.SendAsync(request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                    var disposeResponse_ = true;
                    try
                    {
                        var headers_ = System.Linq.Enumerable.ToDictionary(response_.Headers, h_ => h_.Key, h_ => h_.Value);
                        if (response_.Content != null && response_.Content.Headers != null)
                        {
                            foreach (var item_ in response_.Content.Headers)
                                headers_[item_.Key] = item_.Value;
                        }

                        ProcessResponse(client_, response_);

                        var status_ = (int)response_.StatusCode;
                        if (status_ == 200)
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<System.Collections.Generic.ICollection<User>>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            return objectResponse_.Object;
                        }
                        else
                        if (status_ == 500)
                        {
                            string responseText_ = ( response_.Content == null ) ? string.Empty : await response_.Content.ReadAsStringAsync().ConfigureAwait(false);
                            throw new ApiException("Server Error", status_, responseText_, headers_, null);
                        }
                        else
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Error", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                    }
                    finally
                    {
                        if (disposeResponse_)
                            response_.Dispose();
                    }
                }
            }
            finally
            {
                if (disposeClient_)
                    client_.Dispose();
            }
        }

        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual System.Threading.Tasks.Task<User> DetailsAsync(int? id)
        {
            return DetailsAsync(id, System.Threading.CancellationToken.None);
        }

        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual async System.Threading.Tasks.Task<User> DetailsAsync(int? id, System.Threading.CancellationToken cancellationToken)
        {
            var urlBuilder_ = new System.Text.StringBuilder();
            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/User/Details?");
            if (id != null)
            {
                urlBuilder_.Append(System.Uri.EscapeDataString("id") + "=").Append(System.Uri.EscapeDataString(ConvertToString(id, System.Globalization.CultureInfo.InvariantCulture))).Append("&");
            }
            urlBuilder_.Length--;

            var client_ = _httpClient;
            var disposeClient_ = false;
            try
            {
                using (var request_ = new System.Net.Http.HttpRequestMessage())
                {
                    request_.Method = new System.Net.Http.HttpMethod("GET");
                    request_.Headers.Accept.Add(System.Net.Http.Headers.MediaTypeWithQualityHeaderValue.Parse("text/plain"));

                    PrepareRequest(client_, request_, urlBuilder_);

                    var url_ = urlBuilder_.ToString();
                    request_.RequestUri = new System.Uri(url_, System.UriKind.RelativeOrAbsolute);

                    PrepareRequest(client_, request_, url_);

                    var response_ = await client_.SendAsync(request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                    var disposeResponse_ = true;
                    try
                    {
                        var headers_ = System.Linq.Enumerable.ToDictionary(response_.Headers, h_ => h_.Key, h_ => h_.Value);
                        if (response_.Content != null && response_.Content.Headers != null)
                        {
                            foreach (var item_ in response_.Content.Headers)
                                headers_[item_.Key] = item_.Value;
                        }

                        ProcessResponse(client_, response_);

                        var status_ = (int)response_.StatusCode;
                        if (status_ == 200)
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<User>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            return objectResponse_.Object;
                        }
                        else
                        if (status_ == 404)
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Not Found", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                        else
                        if (status_ == 500)
                        {
                            string responseText_ = ( response_.Content == null ) ? string.Empty : await response_.Content.ReadAsStringAsync().ConfigureAwait(false);
                            throw new ApiException("Server Error", status_, responseText_, headers_, null);
                        }
                        else
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Error", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                    }
                    finally
                    {
                        if (disposeResponse_)
                            response_.Dispose();
                    }
                }
            }
            finally
            {
                if (disposeClient_)
                    client_.Dispose();
            }
        }

        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual System.Threading.Tasks.Task SaveAsync(User body)
        {
            return SaveAsync(body, System.Threading.CancellationToken.None);
        }

        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual async System.Threading.Tasks.Task SaveAsync(User body, System.Threading.CancellationToken cancellationToken)
        {
            var urlBuilder_ = new System.Text.StringBuilder();
            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/User/Save");

            var client_ = _httpClient;
            var disposeClient_ = false;
            try
            {
                using (var request_ = new System.Net.Http.HttpRequestMessage())
                {
                    var json_ = Newtonsoft.Json.JsonConvert.SerializeObject(body, _settings.Value);
                    var content_ = new System.Net.Http.StringContent(json_);
                    content_.Headers.ContentType = System.Net.Http.Headers.MediaTypeHeaderValue.Parse("application/json");
                    request_.Content = content_;
                    request_.Method = new System.Net.Http.HttpMethod("POST");

                    PrepareRequest(client_, request_, urlBuilder_);

                    var url_ = urlBuilder_.ToString();
                    request_.RequestUri = new System.Uri(url_, System.UriKind.RelativeOrAbsolute);

                    PrepareRequest(client_, request_, url_);

                    var response_ = await client_.SendAsync(request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                    var disposeResponse_ = true;
                    try
                    {
                        var headers_ = System.Linq.Enumerable.ToDictionary(response_.Headers, h_ => h_.Key, h_ => h_.Value);
                        if (response_.Content != null && response_.Content.Headers != null)
                        {
                            foreach (var item_ in response_.Content.Headers)
                                headers_[item_.Key] = item_.Value;
                        }

                        ProcessResponse(client_, response_);

                        var status_ = (int)response_.StatusCode;
                        if (status_ == 200)
                        {
                            return;
                        }
                        else
                        if (status_ == 500)
                        {
                            string responseText_ = ( response_.Content == null ) ? string.Empty : await response_.Content.ReadAsStringAsync().ConfigureAwait(false);
                            throw new ApiException("Server Error", status_, responseText_, headers_, null);
                        }
                        else
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Error", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                    }
                    finally
                    {
                        if (disposeResponse_)
                            response_.Dispose();
                    }
                }
            }
            finally
            {
                if (disposeClient_)
                    client_.Dispose();
            }
        }

        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual System.Threading.Tasks.Task DeleteAsync(int? id)
        {
            return DeleteAsync(id, System.Threading.CancellationToken.None);
        }

        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
        /// <returns>Success</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual async System.Threading.Tasks.Task DeleteAsync(int? id, System.Threading.CancellationToken cancellationToken)
        {
            var urlBuilder_ = new System.Text.StringBuilder();
            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/User/Delete?");
            if (id != null)
            {
                urlBuilder_.Append(System.Uri.EscapeDataString("id") + "=").Append(System.Uri.EscapeDataString(ConvertToString(id, System.Globalization.CultureInfo.InvariantCulture))).Append("&");
            }
            urlBuilder_.Length--;

            var client_ = _httpClient;
            var disposeClient_ = false;
            try
            {
                using (var request_ = new System.Net.Http.HttpRequestMessage())
                {
                    request_.Method = new System.Net.Http.HttpMethod("DELETE");

                    PrepareRequest(client_, request_, urlBuilder_);

                    var url_ = urlBuilder_.ToString();
                    request_.RequestUri = new System.Uri(url_, System.UriKind.RelativeOrAbsolute);

                    PrepareRequest(client_, request_, url_);

                    var response_ = await client_.SendAsync(request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                    var disposeResponse_ = true;
                    try
                    {
                        var headers_ = System.Linq.Enumerable.ToDictionary(response_.Headers, h_ => h_.Key, h_ => h_.Value);
                        if (response_.Content != null && response_.Content.Headers != null)
                        {
                            foreach (var item_ in response_.Content.Headers)
                                headers_[item_.Key] = item_.Value;
                        }

                        ProcessResponse(client_, response_);

                        var status_ = (int)response_.StatusCode;
                        if (status_ == 200)
                        {
                            return;
                        }
                        else
                        if (status_ == 404)
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Not Found", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                        else
                        if (status_ == 500)
                        {
                            string responseText_ = ( response_.Content == null ) ? string.Empty : await response_.Content.ReadAsStringAsync().ConfigureAwait(false);
                            throw new ApiException("Server Error", status_, responseText_, headers_, null);
                        }
                        else
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<ProblemDetails>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            throw new ApiException<ProblemDetails>("Error", status_, objectResponse_.Text, headers_, objectResponse_.Object, null);
                        }
                    }
                    finally
                    {
                        if (disposeResponse_)
                            response_.Dispose();
                    }
                }
            }
            finally
            {
                if (disposeClient_)
                    client_.Dispose();
            }
        }

        protected struct ObjectResponseResult<T>
        {
            public ObjectResponseResult(T responseObject, string responseText)
            {
                this.Object = responseObject;
                this.Text = responseText;
            }

            public T Object { get; }

            public string Text { get; }
        }

        public bool ReadResponseAsString { get; set; }

        protected virtual async System.Threading.Tasks.Task<ObjectResponseResult<T>> ReadObjectResponseAsync<T>(System.Net.Http.HttpResponseMessage response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, System.Threading.CancellationToken cancellationToken)
        {
            if (response == null || response.Content == null)
            {
                return new ObjectResponseResult<T>(default(T), string.Empty);
            }

            if (ReadResponseAsString)
            {
                var responseText = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
                try
                {
                    var typedBody = Newtonsoft.Json.JsonConvert.DeserializeObject<T>(responseText, JsonSerializerSettings);
                    return new ObjectResponseResult<T>(typedBody, responseText);
                }
                catch (Newtonsoft.Json.JsonException exception)
                {
                    var message = "Could not deserialize the response body string as " + typeof(T).FullName + ".";
                    throw new ApiException(message, (int)response.StatusCode, responseText, headers, exception);
                }
            }
            else
            {
                try
                {
                    using (var responseStream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
                    using (var streamReader = new System.IO.StreamReader(responseStream))
                    using (var jsonTextReader = new Newtonsoft.Json.JsonTextReader(streamReader))
                    {
                        var serializer = Newtonsoft.Json.JsonSerializer.Create(JsonSerializerSettings);
                        var typedBody = serializer.Deserialize<T>(jsonTextReader);
                        return new ObjectResponseResult<T>(typedBody, string.Empty);
                    }
                }
                catch (Newtonsoft.Json.JsonException exception)
                {
                    var message = "Could not deserialize the response body stream as " + typeof(T).FullName + ".";
                    throw new ApiException(message, (int)response.StatusCode, string.Empty, headers, exception);
                }
            }
        }

        private string ConvertToString(object value, System.Globalization.CultureInfo cultureInfo)
        {
            if (value == null)
            {
                return "";
            }

            if (value is System.Enum)
            {
                var name = System.Enum.GetName(value.GetType(), value);
                if (name != null)
                {
                    var field = System.Reflection.IntrospectionExtensions.GetTypeInfo(value.GetType()).GetDeclaredField(name);
                    if (field != null)
                    {
                        var attribute = System.Reflection.CustomAttributeExtensions.GetCustomAttribute(field, typeof(System.Runtime.Serialization.EnumMemberAttribute)) 
                            as System.Runtime.Serialization.EnumMemberAttribute;
                        if (attribute != null)
                        {
                            return attribute.Value != null ? attribute.Value : name;
                        }
                    }

                    var converted = System.Convert.ToString(System.Convert.ChangeType(value, System.Enum.GetUnderlyingType(value.GetType()), cultureInfo));
                    return converted == null ? string.Empty : converted;
                }
            }
            else if (value is bool) 
            {
                return System.Convert.ToString((bool)value, cultureInfo).ToLowerInvariant();
            }
            else if (value is byte[])
            {
                return System.Convert.ToBase64String((byte[]) value);
            }
            else if (value.GetType().IsArray)
            {
                var array = System.Linq.Enumerable.OfType<object>((System.Array) value);
                return string.Join(",", System.Linq.Enumerable.Select(array, o => ConvertToString(o, cultureInfo)));
            }

            var result = System.Convert.ToString(value, cultureInfo);
            return result == null ? "" : result;
        }
    }

    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class ProblemDetails
    {
        [Newtonsoft.Json.JsonProperty("type", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Type { get; set; }

        [Newtonsoft.Json.JsonProperty("title", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Title { get; set; }

        [Newtonsoft.Json.JsonProperty("status", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public int? Status { get; set; }

        [Newtonsoft.Json.JsonProperty("detail", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Detail { get; set; }

        [Newtonsoft.Json.JsonProperty("instance", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Instance { get; set; }

        private System.Collections.Generic.IDictionary<string, object> _additionalProperties;

        [Newtonsoft.Json.JsonExtensionData]
        public System.Collections.Generic.IDictionary<string, object> AdditionalProperties
        {
            get { return _additionalProperties ?? (_additionalProperties = new System.Collections.Generic.Dictionary<string, object>()); }
            set { _additionalProperties = value; }
        }

    }

    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class User
    {
        [Newtonsoft.Json.JsonProperty("id", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public int Id { get; set; }

        [Newtonsoft.Json.JsonProperty("firstName", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string FirstName { get; set; }

        [Newtonsoft.Json.JsonProperty("lastName", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string LastName { get; set; }

        [Newtonsoft.Json.JsonProperty("email", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Email { get; set; }

    }



    [System.CodeDom.Compiler.GeneratedCode("NSwag", "13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class ApiException : System.Exception
    {
        public int StatusCode { get; private set; }

        public string Response { get; private set; }

        public System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> Headers { get; private set; }

        public ApiException(string message, int statusCode, string response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, System.Exception innerException)
            : base(message + "\n\nStatus: " + statusCode + "\nResponse: \n" + ((response == null) ? "(null)" : response.Substring(0, response.Length >= 512 ? 512 : response.Length)), innerException)
        {
            StatusCode = statusCode;
            Response = response;
            Headers = headers;
        }

        public override string ToString()
        {
            return string.Format("HTTP Response: \n\n{0}\n\n{1}", Response, base.ToString());
        }
    }

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "13.18.2.0 (NJsonSchema v10.8.0.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class ApiException<TResult> : ApiException
    {
        public TResult Result { get; private set; }

        public ApiException(string message, int statusCode, string response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, TResult result, System.Exception innerException)
            : base(message, statusCode, response, headers, innerException)
        {
            Result = result;
        }
    }

}

#pragma warning restore 1591
#pragma warning restore 1573
#pragma warning restore  472
#pragma warning restore  114
#pragma warning restore  108
#pragma warning restore 3016
#pragma warning restore 8603

Having this client makes it much easier to use our web api from client apps (comparing with developing api calls manually). In addition to that NSwagStudio allows to set many different settings which change generated C# code (e.g. include synchronous method in addition to asynchronous which are generated by default, generate interfaces for client classes for simplifying unit testing, default namespace, etc):

You may check other settings when will play with NSwagStudio which for sure worth to spend some time on it. Hope that this knowledge will help to reduce development time and simplify consumption of your web APIs.

Add OpenAPI (Swagger) support to ASP.Net Core Web API

OpenAPI (swagger) support gives many advantages to your web api. One of them is possibility to generate strongly typed clients for calling web api so instead of developing calls from scratch (with HttpClient, building requests, deserialize response, etc) we get ready for use client with POCO classes for requests and response data. In one of my previous articles I wrote how to generate such client for public web api with OpenAPI support: Generate C# client for API with Swagger (OpenAPI) support. In this article I will show how to add OpenAPI support to your own web api project.

We will use ASP.Net Core Web API project for code samples and the following simple controller:

[ApiController]
[Route("[controller]")]
public class UserController : ControllerBase
{
    public UserController()
    {
    }

    [HttpGet]
    [Route("List")]
    public IEnumerable<User> List()
    {
        throw new NotImplementedException();
    }

    [HttpGet]
    [Route("Details")]
    public User Details(int id)
    {
        throw new NotImplementedException();
    }

    [HttpPost]
    [Route("Save")]
    public void Save(User user)
    {
        throw new NotImplementedException();
    }

    [HttpDelete]
    [Route("Delete")]
    public void Delete(int id)
    {
        throw new NotImplementedException();
    }
}

public class User
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
}

First of all we need to add extra nuget package
Swashbuckle.AspNetCore
https://www.nuget.org/packages/Swashbuckle.AspNetCore

It is also possible to add OpenAPI support to web api project from beginning by checking "OpenAPI support" checkbox in create project dialog:

 

Now we need to add few extra lines to Program.cs for configuring Swagger endpoint (lines 7-10 and 15-19):

using Microsoft.OpenApi.Models;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "TestApi", Version = "v1" });
});

var app = builder.Build();

// Configure the HTTP request pipeline.
app.UseSwagger();
app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "TestApi v1");
});

app.UseAuthorization();

app.MapControllers();

app.Run();

Next we need to decorate actions of our controller with additional attributes which will describe which HTTP status codes may be returned from each endpoint, which data can be returned, etc.:

[ApiController]
[Route("[controller]")]
public class UserController : ControllerBase
{
    public UserController()
    {
    }

    [HttpGet]
    [Route("List")]
    [ProducesResponseType(StatusCodes.Status200OK, Type = typeof(List<User>))]
    [ProducesResponseType(StatusCodes.Status500InternalServerError)]
    [ProducesDefaultResponseType]
    public IEnumerable<User> List()
    {
        throw new NotImplementedException();
    }

    [HttpGet]
    [Route("Details")]
    [ProducesResponseType(StatusCodes.Status200OK, Type = typeof(User))]
    [ProducesResponseType(StatusCodes.Status404NotFound)]
    [ProducesResponseType(StatusCodes.Status500InternalServerError)]
    [ProducesDefaultResponseType]
    public User Details(int id)
    {
        throw new NotImplementedException();
    }

    [HttpPost]
    [Route("Save")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status500InternalServerError)]
    [ProducesDefaultResponseType]
    public void Save(User user)
    {
        throw new NotImplementedException();
    }

    [HttpDelete]
    [Route("Delete")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status404NotFound)]
    [ProducesResponseType(StatusCodes.Status500InternalServerError)]
    [ProducesDefaultResponseType]
    public void Delete(int id)
    {
        throw new NotImplementedException();
    }
}

With these declarations Swagger sees that e.g. /details endpoint will return User object if everything went well (when HTTP status code is 200 Ok). Also it may return 404 Not found if user with specified id not found and 500 Internal server error if something went wrong in backend.

Now if we will run our web api and go to http://localhost:{port}/swagger/index.html we will see fancy automatically generated documentation for our api:

We may also expand endpoints and get more information about each of them:

Using these steps we've added OpenAPI support in our ASP.Net Core Web API project. In the next post I will show how to generate api client for this web api running on localhost (update 2023-03-29: see Generate strongly-typed C# client for ASP.Net Core Web API with OpenAPI (swagger) support running on localhost).

Create modern looking CLI tool with command line verbs

More and more CLI tools (command line interface) or simply console apps use unified approach for processing command line arguments. In this post I will write about one way of creating these apps using CommandLineParser. Like it is said on the project's github page CommandLineParser is

API for manipulating command line arguments and related tasks, such as defining switches, options and verb commands

Suppose that we need to create CLI tool for performing basic CRUD operations on some entities (e.g. users) in some data storage. Using syntax of CommandLineParser we may define 4 so called verbs for these operations:

• list - list all users
  
• details - read details of single user
  
• save - insert/update single user
  
• delete - delete single user
  

Verb is logical group of parameters. This is very convenient abstraction because in real life often different operations require different parameters and add them all into one single list of arguments is not convinient.

In our example list doesn't require additional parameters, details and delete operations may require e.g. id property of the user which should be affected by these operations and save may require all other fields (e.g. first name, last name, email, etc - all properties of the user which should be stored to the underlying storage).

When we defined verbs and their parameters we need to create classes for each verb like this (before that we need to add CommandLineParser nuget package to the project):

[Verb("list", HelpText = "List all users from storage")]
public class ListOptions
{
}

[Verb("details", HelpText = "Read details of specific user from storage")]
public class DetailsOptions
{
    [Option("id", Required = true, HelpText = "User id")]
    public string Id { get; set; }
}

[Verb("save", HelpText = "Save user to storage")]
public class SaveOptions
{
    [Option("firstName", Required = true, HelpText = "User first name")]
    public string FirstName { get; set; }

    [Option("lastName", Required = true, HelpText = "User last name")]
    public string LastName { get; set; }

    [Option("email", Required = true, HelpText = "User email")]
    public string Email { get; set; }
}

[Verb("delete", HelpText = "Delete specific user from storage")]
public class DeleteOptions
{
    [Option("id", Required = true, HelpText = "User id")]
    public string Id { get; set; }
}

With these verbs command line processing will look like that:

Parser.Default.ParseArguments<ListOptions, DetailsOptions, SaveOptions, DeleteOptions>(args)
    .WithParsed<ListOptions>(opts => worker.DoWork(opts))
    .WithParsed<DetailsOptions>(opts => worker.DoWork(opts))
    .WithParsed<SaveOptions>(opts => worker.DoWork(opts))
    .WithParsed<DeleteOptions>(opts => worker.DoWork(opts));

In addition to that we need to define 4 methods in the Worker class which will do actual work for each operation:

public class Worker
{
    public void DoWork(ListOptions opt)
    {
    	//...
    }
    
    public void DoWork(DetailsOptions opt)
    {
    	//...
    }
    
    public void DoWork(SaveOptions opt)
    {
    	//...
    }
    
    public void DoWork(DeleteOptions opt)
    {
    	//...
    }
}

That's it. Now lets run our CLI tool without command line parameters - it tell that no verb is specified and will list all available operations with their descriptions:

Based on this list it is clear that we may read all users like this:

CLITool.exe list

If we will run details command without providing id

CLITool.exe details

it will show the following error:

telling us that correct syntax is

CLITool.exe details --id=1

or

CLITool.exe details --id 1

Also we have builtin support of help and version commands. E.g. this is how we may get more information about delete command:

CLITool.exe help delete

which will show us syntax of delete command:

Hope that this information will be useful and we will have more unified CLI tools in future with help of CommandLineParser.