BufferedStream.BeginRead(Byte[], Int32, Int32, AsyncCallback, Object) Method

Reference

Definition

Namespace:: System.IO

Assemblies:: netstandard.dll, System.Runtime.dll

Assembly:: System.Runtime.Extensions.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: BufferedStream.cs

Source:: BufferedStream.cs

Source:: BufferedStream.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Begins an asynchronous read operation. (Consider using ReadAsync(Byte[], Int32, Int32, CancellationToken) instead.)

public:
 override IAsyncResult ^ BeginRead(cli::array <System::Byte> ^ buffer, int offset, int count, AsyncCallback ^ callback, System::Object ^ state);

public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback? callback, object? state);

public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state);

public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object? state);

override this.BeginRead : byte[] * int * int * AsyncCallback * obj -> IAsyncResult

Public Overrides Function BeginRead (buffer As Byte(), offset As Integer, count As Integer, callback As AsyncCallback, state As Object) As IAsyncResult

Parameters

buffer: Byte[]

The buffer to read the data into.

offset: Int32

The byte offset in buffer at which to begin writing data read from the stream.

count: Int32

The maximum number of bytes to read.

callback: AsyncCallback

An optional asynchronous callback, to be called when the read is complete.

state: Object

A user-provided object that distinguishes this particular asynchronous read request from other requests.

Returns

IAsyncResult

An object that represents the asynchronous read, which could still be pending.

Exceptions

ArgumentNullException

buffer is null.

ArgumentOutOfRangeException

offset or count is negative.

IOException

Attempted an asynchronous read past the end of the stream.

ArgumentException

The buffer length minus offset is less than count.

NotSupportedException

The current stream does not support the read operation.

Remarks

In the .NET Framework 4 and earlier versions, you have to use methods such as BeginRead and EndRead to implement asynchronous file operations. These methods are still available in the .NET Framework 4.5 to support legacy code; however, the new async methods, such as ReadAsync, WriteAsync, and FlushAsync, help you implement asynchronous file operations more easily.

EndWrite must be called exactly once for every call to BeginRead. Failing to end a read process before beginning another read can cause undesirable behavior such as deadlock.

Note

Use the CanRead property to determine whether the current instance supports reading.

EndRead must be called with this IAsyncResult to find out how many bytes were read.

Applies to

Product	Versions
.NET	Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

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