How to Read All Text from a File with C# using Async/Await (File.ReadAllTextAsync)

The .NET Framework has some useful static utility functions that make reading files simple, but where are the async versions? In this post I will show you a simple way to create an Asynchronous ReadAllTextAsync function.

File.ReadAllText("example.txt") is really useful, but what if you want to do it using the async/await pattern. I couldn’t find a ReadAllTextAsync method so here is a simple utility class that you can use instead.

Code Example

public static class FileUtil
{
    public static async Task<string> ReadAllTextAsync(string filePath)
    {
        var stringBuilder = new StringBuilder();
        using (var fileStream = File.OpenRead(filePath))
        using (var streamReader = new StreamReader(fileStream))
        {
            string line = await streamReader.ReadLineAsync();
            while(line != null)
            {
                stringBuilder.AppendLine(line);
                line = await streamReader.ReadLineAsync();
            }
            return stringBuilder.ToString();
        }
    }
}

Usage Example

string text = FileUtil.ReadAllTextAsync("example.txt");