问异步方法执行

EN

public double GetSquareRoot(double value)
{
    System.Diagnostics.Debugger.Log(0, "MyService", "Get - Start\n");
    Thread.Sleep(3000);
    System.Diagnostics.Debugger.Log(0, "MyService", "Get - Finish\n");
    return Math.Sqrt(value);
}

public IAsyncResult BeginGetSquareRoot(double value, AsyncCallback callback, object     state)
{
    System.Diagnostics.Debugger.Log(0, "MyService", "Begin - Start\n");
    GetSquareRootAsyncResult asyncResult = new GetSquareRootAsyncResult(callback,     state);
    asyncResult.Value = value;
    ThreadPool.QueueUserWorkItem(new WaitCallback((Callback)), asyncResult);
    System.Diagnostics.Debugger.Log(0, "MyService", "Begin - Finish\n");
    return asyncResult;
}

public double EndGetSquareRoot(IAsyncResult asyncResult)
{
    System.Diagnostics.Debugger.Log(0, "MyService", "End - Start\n");
    double result = 0;
    using (GetSquareRootAsyncResult getSquareRootAsyncResult = asyncResult as      GetSquareRootAsyncResult)
    {
        getSquareRootAsyncResult.AsyncWaitHandle.WaitOne();
        result = getSquareRootAsyncResult.Result;
    }
    System.Diagnostics.Debugger.Log(0, "MyService", "End - Finish\n");
    return result;
}

public partial class Form1 : Form
{
    IMyService m_Client;
    public Form1()
    {
        InitializeComponent();
        ChannelFactory<IMyService> factory = new ChannelFactory<IMyService>("netTcp");
        factory.Open();
        m_Client = factory.CreateChannel();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        double value = 0;
        Double.TryParse(m_ValueTextBox.Text, out value);
        m_Client.BeginGetSquareRoot(value, OnEndGetSquareRoot, null);
        m_StartButton.Enabled = false;
        m_ResultTextBox.Text = @"Loading...";
    }

    public void OnEndGetSquareRoot(IAsyncResult asyncResult)
    {
        this.Invoke(new MethodInvoker(delegate()
            {
                m_ResultTextBox.Text =                             
                    m_Client.EndGetSquareRoot(asyncResult).ToString();
                m_StartButton.Enabled = true;
            }));
    }
}