Fix Azure web job startup error "Storage account connection string 'AzureWebJobsStorage' does not exist"

If you develop continuous Azure web job which monitors e.g. Azure storage queue messages then your code may look like this (in our example we will use latest v3 version of Microsoft.Azure.WebJobs):

var builder = new HostBuilder();
static void Main(string[] args)
{
    var builder = new HostBuilder();
    builder.UseEnvironment("development");
    builder.ConfigureWebJobs(b =>
    {
        b.AddAzureStorageCoreServices();
        b.AddAzureStorage();
    });
    builder.ConfigureLogging((context, b) =>
    {
        b.AddConsole();
    });
    var host = builder.Build();
    using (host)
    {
        host.Run();
    }
}

public static void ProcessQueueMessage([QueueTrigger("myqueue")] string message, TextWriter log)
{
    ...
}

Here in Main method (which is entry point for continuous web job) we create host which subscribes on specified queue. When new message will be added to the queue it should trigger our ProcessQueueMessage handler. However on startup you may get the following error:

Storage account connection string 'AzureWebJobsStorage' does not exist

This error is thrown when host can't find connection string AzureWebJobsStorage of Azure storage where specified queue is located. In order to avoid this error we need to create appsettings.json file in our project which looks like this:

{
  "ConnectionStrings": {
    "AzureWebJobsStorage": "..."
  }
}

Also in file's properties we need to set Copy to output directory = Copy always so it will be always copied in output directory with exe file. After that error should disappear and web job should be successfully started.