Question

在下面的BaseStream.Seek代码中，我收到运行时错误NullReferenceException未被用户代码处理。对象引用未设置为对象的实例。

我该如何解决这个问题？

public void GoButton_Click(object sender, System.EventArgs e)
{
    IAsyncResult ar = DoSomethingAsync(strURL, strInput);
    Session["result"] = ar;
    Response.Redirect("wait1.aspx");
}

private IAsyncResult DoSomethingAsync(string strURL, string strInput)
{
    DoSomethingDelegate doSomethingDelegate = new DoSomethingDelegate(DoSomething);
    IAsyncResult ar = doSomethingDelegate.BeginInvoke(strURL, strInput, new AsyncCallback(MyCallback), null);
    return ar;
}

private delegate void DoSomethingDelegate(string strURL, string strInput);

private void MyCallback(IAsyncResult ar)
{
    AsyncResult aResult = (AsyncResult)ar;
    DoSomethingDelegate doSomethingDelegate = (DoSomethingDelegate)aResult.AsyncDelegate;
    doSomethingDelegate.EndInvoke(ar);
}

private void DoSomething(string strURL, string strInput)
{
    int i = 0;
    for (i = 0; i < 1000; i++)
    {
        m_streamWriter.BaseStream.Seek(0, SeekOrigin.End);
        m_streamWriter.WriteLine("{0} ", MethodCall(strURL, strInput));
        m_streamWriter.Flush();
        m_streamWriter.Close();
    }
}

Answer 1

您正在关闭流，然后尝试在for循环的下一次迭代中调用它上的Seek（） - 这看起来很适合作为异常的来源

Answer 2

for (i = 0; i < 1000; i++) 
    { 
        m_streamWriter.BaseStream.Seek(0, SeekOrigin.End); 
        m_streamWriter.WriteLine("{0} ", MethodCall(strURL, strInput)); 
    } 
    m_streamWriter.Flush(); 
    m_streamWriter.Close();

尝试将m_streamWriter.Close移出循环。

Answer 3

您正尝试将Seek和WriteLine打开到封闭的流中。

编辑：哦，伊恩更快。

对象引用未设置为对象的实例 - BaseStream.Seek

3 个答案: