FileStream.EndRead(IAsyncResult) 方法
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
等待挂起的异步读操作完成。 （请考虑改用 ReadAsync(Byte[], Int32, Int32, CancellationToken)。）
public:
override int EndRead(IAsyncResult ^ asyncResult);public override int EndRead (IAsyncResult asyncResult);override this.EndRead : IAsyncResult -> intPublic Overrides Function EndRead (asyncResult As IAsyncResult) As Integer- asyncResult
- IAsyncResult
对所等待的挂起异步请求的引用。
从流中读取的字节数，介于 0 和所请求的字节数之间。 流仅在流结尾返回 0，否则在至少有 1 个字节可用之前应一直进行阻止。
asyncResult 为 null。
此 IAsyncResult 对象不是通过对该类调用 BeginRead(Byte[], Int32, Int32, AsyncCallback, Object) 来创建的。
流已关闭或出现了内部错误。
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 EndReadCallback( IAsyncResult^ asyncResult )
{
State^ tempState = dynamic_cast<State^>(asyncResult->AsyncState);
int readCount = tempState->FStream->EndRead( asyncResult );
int i = 0;
while ( i < readCount )
{
if ( tempState->ReadArray[ i ] != tempState->WriteArray[ i++ ] )
{
Console::WriteLine( "Error writing data." );
tempState->FStream->Close();
return;
}
}
Console::WriteLine( "The data was written to {0} "
"and verified.", tempState->FStream->Name );
tempState->FStream->Close();
// Signal the main thread that the verification is finished.
tempState->ManualEvent->Set();
}
public:
static void EndReadCallback(IAsyncResult asyncResult)
{
State tempState = (State)asyncResult.AsyncState;
int readCount = tempState.FStream.EndRead(asyncResult);
int i = 0;
while(i < readCount)
{
if(tempState.ReadArray[i] != tempState.WriteArray[i++])
{
Console.WriteLine("Error writing data.");
tempState.FStream.Close();
return;
}
}
Console.WriteLine("The data was written to {0} and verified.",
tempState.FStream.Name);
tempState.FStream.Close();
// Signal the main thread that the verification is finished.
tempState.ManualEvent.Set();
}
let endReadCallback (asyncResult: IAsyncResult) =
let tempState = asyncResult.AsyncState :?> State
let readCount = tempState.FStream.EndRead asyncResult
let mutable i = 0
let mutable errored = false
while i < readCount do
if tempState.ReadArray[i] <> tempState.WriteArray[i] then
printfn "Error writing data."
tempState.FStream.Close()
errored <- true
i <- readCount
i <- i + 1
printfn $"The data was written to {tempState.FStream.Name} and verified."
tempState.FStream.Close()
// Signal the main thread that the verification is finished.
tempState.ManualEvent.Set() |> ignore
Private Shared Sub EndReadCallback(asyncResult As IAsyncResult)
Dim tempState As State = _
DirectCast(asyncResult.AsyncState, State)
Dim readCount As Integer = _
tempState.FStream.EndRead(asyncResult)
Dim i As Integer = 0
While(i < readCount)
If(tempState.ReadArray(i) <> tempState.WriteArray(i))
Console.WriteLine("Error writing data.")
tempState.FStream.Close()
Return
End If
i += 1
End While
Console.WriteLine("The data was written to {0} and " & _
"verified.", tempState.FStream.Name)
tempState.FStream.Close()
' Signal the main thread that the verification is finished.
tempState.ManualEvent.Set()
End Sub
在 .NET Framework 4 及更早版本中，必须使用 和 EndRead 等BeginRead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。
EndRead 每次调用 BeginRead都必须完全调用 。 在开始另一个读取之前未能结束读取进程可能会导致不良行为，例如死锁。
此方法重写 EndRead。
EndRead可以从 中对每个IAsyncResultBeginRead调用 。 调用 EndRead 会告知从流中读取的字节数。 EndRead 将阻止，直到 I/O 操作完成。
| 产品 | 版本 |
|---|---|
| .NET | Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 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 |
