StreamReader.ReadLineAsync Method

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

public:
 override System::Threading::Tasks::Task<System::String ^> ^ ReadLineAsync();

public override System.Threading.Tasks.Task<string> ReadLineAsync();

public override System.Threading.Tasks.Task<string?> ReadLineAsync();

[System.Runtime.InteropServices.ComVisible(false)]
public override System.Threading.Tasks.Task<string> ReadLineAsync();

override this.ReadLineAsync : unit -> System.Threading.Tasks.Task<string>

[<System.Runtime.InteropServices.ComVisible(false)>]
override this.ReadLineAsync : unit -> System.Threading.Tasks.Task<string>

Public Overrides Function ReadLineAsync () As Task(Of String)

Returns

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.

Attributes

ComVisibleAttribute

Exceptions

Examples

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 async Task Main()
 {
 await ReadCharacters();
 }

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

Imports System.IO

Module Module1

 Sub Main()
 ReadCharacters()
 End Sub

 Async Sub ReadCharacters()
 Dim result As String

 Using reader As StreamReader = File.OpenText("existingfile.txt")
 Console.WriteLine("Opened file.")
 result = Await reader.ReadLineAsync()
 Console.WriteLine("First line contains: " + result)
 End Using
 End Sub
End Module

Remarks

This method stores in the task it returns all non-usage exceptions that the method's synchronous counterpart can throw. If an exception is stored into the returned task, that exception will be thrown when the task is awaited. Usage exceptions, such as ArgumentException, are still thrown synchronously. For the stored exceptions, see the exceptions thrown by ReadLine().

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

Source:

StreamReader.cs

public:
 override System::Threading::Tasks::ValueTask<System::String ^> ReadLineAsync(System::Threading::CancellationToken cancellationToken);

public override System.Threading.Tasks.ValueTask<string?> ReadLineAsync(System.Threading.CancellationToken cancellationToken);

override this.ReadLineAsync : System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<string>

Public Overrides Function ReadLineAsync (cancellationToken As CancellationToken) As ValueTask(Of String)

Parameters

Returns

A value 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 of the characters have been read.

Exceptions

Remarks

If this method is canceled via cancellationToken, some data that has been read from the current Stream but not stored (by the StreamReader) or returned (to the caller) may be lost.

This method stores in the task it returns all non-usage exceptions that the method's synchronous counterpart can throw. If an exception is stored into the returned task, that exception will be thrown when the task is awaited. Usage exceptions, such as ArgumentException, are still thrown synchronously. For the stored exceptions, see the exceptions thrown by ReadLine().