System.Windows.Forms.Control.get_Handle()
   System.Windows.Forms.Control.set_WindowText(String value)
   System.Windows.Forms.Control.set_Text(String value)
   System.Windows.Forms.Label.set_Text(String value)
在 set_WindowText 方法中通过
UnsafeNativeMethods.SetWindowText(new HandleRef(this.window, this.Handle), value);
去设置Text，这里要访问Handle，确保Handle正确，就会使用get_Handle，代码如下


public IntPtr get_Handle()
{
//这里会检查
    if ((checkForIllegalCrossThreadCalls && !inCrossThreadSafeCall) && this.InvokeRequired)
    {
        throw new InvalidOperationException(SR.GetString("IllegalCrossThreadCall", new object[] { this.Name }));
    }
    if (!this.IsHandleCreated)
    {
        this.CreateHandle();
    }
    return this.HandleInternal;
}

设置BackGroundImage时，代码中不需要检查Handle
public virtual Image BackgroundImage
{
    get
    {
        return (Image) this.Properties.GetObject(PropBackgroundImage);
    }
    set
    {
        if (this.BackgroundImage != value)
        {
            this.Properties.SetObject(PropBackgroundImage, value);
            this.OnBackgroundImageChanged(EventArgs.Empty);
        }
    }
}