C＃＆QUOT; InvalidCastException的＆QUOT;试图从TimerCallback访问WebBrowser控件时

问题描述

基本上我有同样的问题，因为该用户：
How检查的TrackBar鼠标滑动保持和释放
我解决了这个使用所提供的第一个解决方案。然而，当计时器被调用时，我想打电话给InvokeScript上WebBrowser控件。 InvokeScript运行没有错误，但JavaScript函数永远不会被调用。当我把这个脚本就像一个按钮点击事件处理程序，函数正确调用。

Basically I have the same problem as this user: How to check for TrackBar sliding with mouse hold and releaseI fixed this using the first solution provided. However, when the timer is called, I want to call InvokeScript on a webbrowser control. InvokeScript runs without an error, but the javascript function is never called. When I call this script from like a button clicked event handler, the function is called properly.

我发现，当我尝试从WebBrowser控件访问属性（比如MessageBox.Show（webBrowser1.DocumentText），这将引发一个InvalidCastException的。

I found out that when I try to access properties from the webbrowser control (like MessageBox.Show(webBrowser1.DocumentText), this throws a InvalidCastException.

// in constructor:
webBrowser1.AllowWebBrowserDrop = false;
webBrowser1.IsWebBrowserContextMenuEnabled = false;
webBrowser1.WebBrowserShortcutsEnabled = false;
webBrowser1.ObjectForScripting = this;
timer = new System.Threading.Timer(this.TimerElapsed);     

private void trackBar2_ValueChanged(object sender, EventArgs e)
{
        timer.Change(500, -1);
}
private void TimerElapsed(object state)
{
    this.webBrowser1.InvokeScript("jmp_end");
    MessageBox.Show(this.webBrowser1.DocumentText);
    timerRunning = false;
}
private void TimerElapsed(object state)
{
    WebBrowser brw = getBrowser();
    brw.Document.InvokeScript("jmpend");
    MessageBox.Show(brw.DocumentText);
    timerRunning = false;
}

有谁知道我在做什么错在这里？还是有另一种方式来获得同样的结果？

Does anyone know what I am doing wrong here? Or is there another way to get the same result?

在约InvokeRequired的意见，这听起来完全像我所需要的。但我不能得到它的工作。这是我从样品code从制作的

After comments about InvokeRequired, this sounds exactly like what I need.. But I can't get it working.. This is what I made from the sample code from C# System.InvalidCastException

public delegate WebBrowser getBrowserHandler();
public WebBrowser getBrowser()
{
    if (InvokeRequired)
    {
        return Invoke(new getBrowserHandler(getBrowser)) as WebBrowser;
    }
    else
    {
        return webBrowser1;
    }
}

private void TimerElapsed(object state)
{
    WebBrowser brw = getBrowser();
    brw.Document.InvokeScript("jmpend");
    MessageBox.Show(brw.DocumentText);
    timerRunning = false;
}

有什么我错过了吗？

What have I missed here?

推荐答案

主叫方（定时器）是比对照创建在不同的线程。

The caller (the timer) is on a different thread than the control was created on.

请参阅

Sample code that should address your issue is posted on this question: C# System.InvalidCastException

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