CODEWITHSUNDEEP
c#windowswindows-8winrt-xamlasync-await
Paytime
Paytime

Reputation: 23

How do I wait for an async to complete?

I am currently working on a Chat Client(Windows Store apps - C#) and I'm currently stuck at the registration part. Before I send the relevant data like username, password, email etc. to the server to make a new user, I call the function "CheckSignUp(...)" which checks first if the username already exists. It first sends the keyword /F011/ and then the username, then I should the receive the keyword OK or NOK(username already exists). Here's the code:

public async Task<string> CheckSignUp(string username)
    {
        writer.WriteString("/F011/" + "\n");
        writer.WriteString(username + "\n");
        await writer.StoreAsync();

        reader.InputStreamOptions = InputStreamOptions.Partial;
        string result = reader.ReadString(await reader.LoadAsync(3));
        return result;
    }

This function is called when I press the "Sign Up" button. The problem is that I get the error only after the 2nd time I've pressed the "Sign Up" button. Here's the relevant code for the Button_click event:

private async void bnSignUp_Click(object sender, RoutedEventArgs e)
    {
           ...

            string ValidUser = await App.ChatConnection.CheckSignUp(tbUserName.Text);
            if (ValidUser == "NOK")
            {
                FailText.Children.Add(new InfoTextBox("Error! Username already exists."));
                tbUserName.Text = "";
            }
            ....
    }

The creation of the reader and writer objects occurs when connection to the server is made:

socket = new StreamSocket(); 
HostName hostname = new HostName(host); 
await socket.ConnectAsync(hostname, port); 
writer = new DataWriter(socket.OutputStream); 
reader = new DataReader(socket.InputStream);

EDIT: I also have the same problem when I try to log in(the Login() function works similar like the CheckSignUp one):

public async Task<string> Login(string username, string password)
    {
        writer.WriteString("/F050/" + "\n");
        writer.WriteString(GetHash(password) + "\n");
        writer.WriteString("\n");
        writer.WriteString(username + "\n");
        await writer.StoreAsync();

        reader.InputStreamOptions = InputStreamOptions.Partial;
        return reader.ReadString(await reader.LoadAsync(3));
    }

Upvotes: 1

Views: 258

Answers (2)

Stephen Cleary
Stephen Cleary

Reputation: 457207

I recommend that you first do your best to not use TCP/IP. Use WebAPI, SignalR, etc.

If you do need to use TCP/IP, then you'll need to implement message framing, as I describe on my blog.

Upvotes: 2

YK1
YK1

Reputation: 7622

You may have to flush the writer so that your data is actually sent over socket and not buffered.

public async Task<string> CheckSignUp(string username)
{
    writer.WriteString("/F011/" + "\n");
    writer.WriteString(username + "\n");
    await writer.StoreAsync();

    await writer.FlushAsync();

    // ..rest of code...
}

Upvotes: 0

Related Questions