没有可用控件时如何调用()

问题描述

我正在编写一个连接处理程序(一个请求用户名和密码的对话框).该代码是显示对话框的处理程序.可以从线程中调用此代码，因此如果InvokeRequired，则需要Invoke().

I'm writing a connection handler (a dialog to request username and password). The code is a handler that shows a dialog. This code could be called from a thread, so I need to Invoke() if InvokeRequired.

在理想情况下，我可以使用Control初始化处理程序以执行InvokeRequired，但是有时Control可以为null.是否有可能?如何实现代码?以下正确吗?

In a ideal situation I can initialize then handler with a Control to do InvokeRequired, but sometimes the Control could be null. Is it possible? How could I implement the code? Is the following correct?

public class GuiCredentialsHandler
{
    // control used to invoke if needed
    private static Control mInvokeControl;

    /// <summary>
    /// Initialize a GetCredentials handler for current process.
    /// This method should be always called from the main thread, for
    /// a correctly handling for invokes (when the handler is called
    /// from a thread).
    /// </summary>
    /// <param name="parentControl">Application top form.
    /// Can be null if unknown</param>
    public static void Initialize(Control parentControl)
    {
        if (parentControl != null)
        {
            mInvokeControl = parentControl;
        }
        else
        {
            mInvokeControl = new Control();
            // force to create window handle
            mInvokeControl.CreateControl();
        }
    }

    public static Credentials GetCredentials()
    {
        if (mInvokeControl.InvokeRequired)
        {
            return mInvokeControl.Invoke(
                new GetCredentialsDelegate(DoGetCredentials), null)
                as Credentials;
        }
        else
        {
            return DoGetCredentials();
        }
    }

    private static Credentials DoGetCredentials()
    {
        // the code stuff goes here
    }

}

我的问题是:

1. 如果将空控件传递给InitializeMethod()
会发生什么?
2. 如果在UIThread中执行Initialize()方法，该代码以后是否可以工作?
3. 如果您没有任何控件可以测试InvokeRequired，推荐的模式是什么?

1. What happens if I pass a null control to the InitializeMethod()
2. If the Initialize() method is executed in the UIThread, will the code work later?
3. What is the recommended pattern if you havn't got any control to test InvokeRequired?

预先感谢

EDIT :做一些测试，我意识到如果将null传递给Initialize()，则该控件未在UI线程中运行，因此InvokeRequired似乎返回false.总是.所以我的问题是，当我无法控制时如何执行真正的(可靠的)调用?

EDIT: Doing some tests, I have realized that if I pass null to Initialize(), the control is not running in the UI thread so the InvokeRequired seems to return false. Always. So my question is, how can I perform a real (fiable) Invoke when I have no control?

EDIT2 :进行mInvokeControl.CreateControl()解决了该问题.

EDIT2: Doing mInvokeControl.CreateControl() fixs the issue.

推荐答案

一个简单的解决方案是在主线程中创建一个不可见的控件，您的工作线程可以在该控件上调用Invoke.

A simple solution is to create an invisible control in the main thread on which your worker threads can call Invoke.

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