Unable to use async-await with AcceptTcpClientAsync method

Question

I saw a lot of code snippets like here:

TcpClient client = await listener.AcceptTcpClientAsync();
Logger.Info("Client accepted");

https://codereview.stackexchange.com/questions/33748/wpf-async-await-tcpclient-tcplistener-sample

var tcpClient = await listener.AcceptTcpClientAsync();
HandleConnectionAsync(tcpClient);

https://bsmadhu.wordpress.com/2012/09/29/simplify-asynchronous-programming-with-c-5-asyncawait/

It seems like it works for the most of people. Unfortunately, it doesn't work for me -- compiler gives me the following error:

error CS4033: The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task'

What am I doing wrong? How can I fix it?

Answer 1

What am I doing wrong?

Exactly as the error states, the calling method needs to be marked with the async modifier and have a return type of Task or Task<T> :

public async Task ConnectAsync()
{
    TcpClient client = await listener.AcceptTcpClientAsync();
    Logger.Info("Client accepted");
}