Quick Answer

Properly await async methods.

Understanding the Issue

Occurs when awaiting non-task values. Only methods returning Task/Task<T> can be awaited. void methods should return Task.

The Problem

This code demonstrates the issue:

Csharp Error 
async void BadAsync() {
    await Task.Delay(100);
    return "result"; // Error
}

The Solution

Here's the corrected code:

Csharp Fixed 
// Solution 1: Return Task<T>
async Task<string> GoodAsync() {
    await Task.Delay(100);
    return "result";
}

// Solution 2: Proper void handling
async Task DoWorkAsync() {
    await Task.Run(() => {/* work */});
}

// Solution 3: Consume properly
public async Task Process() {
    string result = await GoodAsync();
}

Key Takeaways

Always return Task/Task<T> from async methods.