Run Azure function as Web job without code change

Sometime it may be needed to test existing Azure function as Web job (e.g. if you decide to move some long-running process from AF to web job). In order to do that you need to create App service first. After that create new console app project in Visual Studio, reference your Azure functions project as it would be regular class library and from Program.cs call necessary Azure function (it is possible since AFs are created as static methods of the class).

The problem however is that if you read some app settings in Azure function code – you most probably do it like that:

string foo = Environment.GetEnvironmentVariable("Foo", EnvironmentVariableTarget.Process);

But if you will just copy AF app settings to appSettings section of app.config of the new console project then above code will return empty string for any app setting. So in order to call our Azure function from console application and run it as web job we need to perform additional step: iterate through all app settings and fill environment variables for the process:

var appSettings = ConfigurationManager.AppSettings;
foreach (var key in appSettings.AllKeys)
{
 Environment.SetEnvironmentVariable(key, appSettings[key],
  EnvironmentVariableTarget.Process);
}

After that app settings will be successfully read and Azure function may run as web job without changing its code.