使用Xamarin开发跨平台应用程序时使用C＃从Azure存储帐户表中检索记录，并给出错误

Question

Retrieving records from Azure Storage account table using c# while developing cross platform app using xamarin giving error.

await tbl.ExecuteAsync(retrieveOperation);

I AM FOLLOWING THIS LINK !

This code gives exception (Time awaiting and Async error using storageexception) when ILogin() is executed separately ie not through the Logmein().

When I run Logmein() with the code in current form, nothing happens ie not exception error occurs.

When i use task.Wait(); exception/error occurs related to wait. I'll try to provide exception details.

My code is here

    private void Logmein()
     {

             var task = Task.Run(async () => { await Ilogin(); });// Nothing happens by this code
             //task.Wait(); It gives error/Exception.}
private static async Task Ilogin()
    {

        // Rest of the code is right (TESTED)
        Microsoft.WindowsAzure.Storage.Table.CloudTable table = tableClient.GetTableReference("user");

        Entry uname = new Entry();
        Entry pword = new Entry();
        Label linfo = new Label();
        string userid = uname.Text.ToString();
        string passcode = pword.Text.ToString();
        Reg signuser = new Reg(userid);
        TableOperation retrieveOperation = TableOperation.Retrieve<Reg>("regform", userid);
        TableResult retrievedResult = await tbl.ExecuteAsync(retrieveOperation); //This AWAIT is making trouble
        Reg loginuser = (Reg)retrievedResult.Result;
        string u1 = loginuser.username.ToString();
        string p1 = loginuser.password.ToString();

        if (u1 == userid && p1 == passcode)
        {
            linfo.Text = "Login Successful";
            //await Navigation.PushAsync(new MainPage());
        }
        else
        {
            linfo.Text = "Invalid Username or Password";
        }
    }

// here is my exception handling code

catch (Exception ex)
         {
             linfo.Text = "login Login Error" + ex.Message + ex.StackTrace + ex.HelpLink + ex.Source;
         }

THANKS in advance.

Answer 1

Either go asynchronous all the way or synchronous all the way. Try to avoid mixing the two.

Task Ilogin() is an asynchronous method while void Logmein() is not

it should be made async and then awaited

private async Task Logmein() {
    await Ilogin();
}

There is no need for the Task.Run with fire and forget methods as their exception cannot be caught. Plus mixing blocking calls like Task.Wait() and Task.Result can lead to deadlocks.

if Logmein() needs to be invoked try putting it in an event handler, which would allow for async void so that it can be awaited.

private async void SomeHandler(object sender, EventArgs args) {
    await Logmein();
}

If that is the case you can avoid Logmein() and await Ilogin() directly.

Reference Async/Await - Best Practices in Asynchronous Programming