ExecutionContext in Azure Function IWebJobsStartup implementation

You don't have the ExecutionContext since your Azure Function is not yet processing an actual function call. But you don't need it either - the local.settings.json is automatically parsed into the environment variables.

If you really need the directory, you can use %HOME%/site/wwwroot in Azure, and AzureWebJobsScriptRoot when running locally. This is the equivalent of FunctionAppDirectory.

This is also a good discussion about this topic.

    public void Configure(IWebJobsBuilder builder)
    {
        var local_root = Environment.GetEnvironmentVariable("AzureWebJobsScriptRoot");
        var azure_root = $"{Environment.GetEnvironmentVariable("HOME")}/site/wwwroot";

        var actual_root = local_root ?? azure_root;

        var config = new Microsoft.Extensions.Configuration.ConfigurationBuilder()
            .SetBasePath(actual_root)
            .AddJsonFile("SomeOther.json")
            .AddEnvironmentVariables()
            .Build();

        var appInsightsSetting = config.GetSection("APPINSIGHTS_INSTRUMENTATIONKEY");
        string val = appInsightsSetting.Value;
        var helloSetting = config.GetSection("hello");
        string val = helloSetting.Value;

        //...
    }

Example local.settings.json:

{
  "IsEncrypted": false,
  "Values": {
    "APPINSIGHTS_INSTRUMENTATIONKEY": "123456..."
  }
}

Example SomeOther.json

{
  "hello":  "world"
}