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StreamReader.ReadLineAsync Method

.NET Framework 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)

[ComVisibleAttribute(false)]
[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.

ExceptionCondition
ArgumentOutOfRangeException

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

ObjectDisposedException

The stream has been disposed.

InvalidOperationException

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

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

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)
        {
            ReadCharacters();
        }

        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);
            }
        }
    }
}

.NET Framework

Supported in: 4.6, 4.5

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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