C# 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’.

C# 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’.

Reason for the Error & Solution

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’.

Example

The following sample generates CS4033:

// CS4033.cs (7,9)

using System.Collections.Generic;
class C
{
    void M(IAsyncEnumerable<int> collection)
    {
        await foreach (var i in collection)
        {
        }
    }
}

To correct this error

To correct this error, change the signature of method M to make it asynchronous:

using System.Collections.Generic;
class C
{
    async void M(IAsyncEnumerable<int> collection)
    {
        await foreach (var i in collection)
        {
        }
    }
}