ReadLineAsync Method

StreamReader.ReadLineAsync Method ()

.NET Framework 4.6 and 4.5

Reads a line of characters asynchronously from the current stream and returns the data as a string.

Namespace:   System.IO
Assembly:  mscorlib (in mscorlib.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public override Task<string> ReadLineAsync()

Return Value

Type: System.Threading.Tasks.Task<String>

A task that represents the asynchronous read operation. The value of the TResult parameter contains the next line from the stream, or is null if all the characters have been read.

Exception Condition

The number of characters in the next line is larger than MaxValue.


The stream has been disposed.


The reader is currently in use by a previous read operation.

The following example shows how to read the first line of a file by using the ReadLineAsync() method.

using System;
using System.IO;

namespace ConsoleApplication
    class Program
        static void Main(string[] args)

        static async void ReadCharacters()
            String result;
            using (StreamReader reader = File.OpenText("existingfile.txt"))
                Console.WriteLine("Opened file.");
                result = await reader.ReadLineAsync();
                Console.WriteLine("First line contains: " + result);

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.5
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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