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IAsyncEnumerable<T>

Context: IAsyncEnumerable<T> is the asynchronous version of IEnumerable<T>. It allows asynchronous iteration with await foreach.

using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;

public class FileReader
{
    public async IAsyncEnumerable<string> ReadLinesAsync(string filePath)
    {
        using var reader = new StreamReader(filePath);
        string line;
        while ((line = await reader.ReadLineAsync()) != null)
        {
            yield return line;
        }
    }
}

Benefits

No need to buffer all data in memory.
Each element can be produced asynchronously.
Works with await foreach.

Real-world usage example

Database streaming: In EF Core, AsAsyncEnumerable() returns IAsyncEnumerable<T> for streaming query results.

Example: EF Core async streaming