FileStream.EndWrite(IAsyncResult) 方法

定义

命名空间:

System.IO

程序集:

System.Runtime.dll

Source:

FileStream.cs

结束异步写入操作，在 I/O 操作完成之前一直阻止。 （请考虑改用 WriteAsync(Byte[], Int32, Int32, CancellationToken)。）

public:
 override void EndWrite(IAsyncResult ^ asyncResult);

public override void EndWrite (IAsyncResult asyncResult);

override this.EndWrite : IAsyncResult -> unit

Public Overrides Sub EndWrite (asyncResult As IAsyncResult)

参数

asyncResult

IAsyncResult

挂起的异步 I/O 请求。

例外

ArgumentNullException

asyncResult 为 null。

ArgumentException

此 IAsyncResult 对象不是通过对该类调用 BeginWrite(Byte[], Int32, Int32, AsyncCallback, Object) 来创建的。

InvalidOperationException

多次调用了EndWrite(IAsyncResult) 。

IOException

流已关闭或出现了内部错误。

示例

此代码示例是为构造函数提供的更大示例的 FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean) 一部分。

   static void EndWriteCallback( IAsyncResult^ asyncResult )
   {
      State^ tempState = dynamic_cast<State^>(asyncResult->AsyncState);
      FileStream^ fStream = tempState->FStream;
      fStream->EndWrite( asyncResult );
      
      // Asynchronously read back the written data.
      fStream->Position = 0;
      asyncResult = fStream->BeginRead( tempState->ReadArray, 0, tempState->ReadArray->Length, gcnew AsyncCallback( &FStream::EndReadCallback ), tempState );
      
      // Concurrently do other work, such as 
      // logging the write operation.
   }

};

static void EndWriteCallback(IAsyncResult asyncResult)
{
    State tempState = (State)asyncResult.AsyncState;
    FileStream fStream = tempState.FStream;
    fStream.EndWrite(asyncResult);

    // Asynchronously read back the written data.
    fStream.Position = 0;
    asyncResult = fStream.BeginRead(
        tempState.ReadArray, 0 , tempState.ReadArray.Length,
        new AsyncCallback(EndReadCallback), tempState);

    // Concurrently do other work, such as
    // logging the write operation.
}

let endWriteCallback (asyncResult: IAsyncResult) =
    let tempState = asyncResult.AsyncState :?> State
    let fStream = tempState.FStream
    fStream.EndWrite asyncResult

    // Asynchronously read back the written data.
    fStream.Position <- 0

    let asyncResult =
        fStream.BeginRead(tempState.ReadArray, 0, tempState.ReadArray.Length, AsyncCallback endReadCallback, tempState)

    // Concurrently do other work, such as
    // logging the write operation.
    ()

Private Shared Sub EndWriteCallback(asyncResult As IAsyncResult)
    Dim tempState As State = _
        DirectCast(asyncResult.AsyncState, State)
    Dim fStream As FileStream = tempState.FStream
    fStream.EndWrite(asyncResult)

    ' Asynchronously read back the written data.
    fStream.Position = 0
    asyncResult = fStream.BeginRead( _ 
        tempState.ReadArray, 0 , tempState.ReadArray.Length, _
        AddressOf EndReadCallback, tempState)

    ' Concurrently do other work, such as 
    ' logging the write operation.
End Sub

注解

在 .NET Framework 4 及更早版本中，必须使用 和 EndWrite 等BeginWrite方法来实现异步文件操作。 这些方法在 .NET Framework 4.5 中仍然可用，以支持旧代码;但是，新的异步方法（如 ReadAsync、WriteAsync、 CopyToAsync和 FlushAsync）可帮助你更轻松地实现异步文件操作。

此方法重写 EndWrite。

EndWrite 必须对 中的每个 IAsyncResult 调用 BeginWrite一次。 EndWrite 将阻止，直到 I/O 操作完成。

另请参阅

• 文件和流 I/O
• 如何：从文件中读取文本
• 如何：将文本写入文件
• 异步文件 I/O