extension method in Azure Functions

AzureFunctionSample.cs

using System.Net;
using System.Threading.Tasks;

static string MyExtension(this int num)
{
    return "my extension";
}

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log)
{
    log.Verbose($"C# HTTP trigger function processed a request. RequestUri={req.RequestUri}");

    // parse query parameter
    string name = req.GetQueryNameValuePairs()
        .FirstOrDefault(q => string.Compare(q.Key, "name", true) == 0)
        .Value;

    // Get request body
    dynamic data = await req.Content.ReadAsAsync<object>();

    // Set name to query string or body data
    name = name ?? data?.name;

    return name == null
        ? req.CreateResponse(HttpStatusCode.BadRequest, "Please pass a name on the query string or in the request body")
        : req.CreateResponse(HttpStatusCode.OK, "Hello " + name + 4.MyExtension());
}