WebBrowser屏蔽alert是用重定义alert,confirm实现的。比较简单。代码如下：
添加 com 引用 microsoft html object library
using mshtml;

1、页面一加载就有弹出框的自动点击(屏蔽)

private void webBrowser1_Navigated(object sender, WebBrowserNavigatedEventArgs e)
{
IHTMLWindow2 win = (IHTMLWindow2)webBrowser1.Document.Window.DomWindow;
string s = @"function confirm() {return true;}";
s += @"function alert() {}";
win.execscript(s, "javascript");
}

private void webBrowser1_Navigated(object sender, WebBrowserNavigatedEventArgs e)
      {
          //自动点击弹出确认或弹出提示
          IHTMLDocument2 vDocument = (IHTMLDocument2)webBrowser1.Document.DomDocument;
          vDocument.parentWindow.execscript("function confirm(str){return true;} ", "javascript"); //弹出确认
          vDocument.parentWindow.execscript("function alert(str){return true;} ", "javascript");//弹出提示
      }

2、WebBrowser页面加载完毕之后，在页面中进行一些自动化操作的时候弹出框的自动点击(屏蔽)

private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            //自动点击弹出确认或弹出提示
            IHTMLDocument2 vDocument = (IHTMLDocument2)webBrowser1.Document.DomDocument;
            vDocument.parentWindow.execscript("function confirm(str){return true;} ", "javascript"); //弹出确认
            vDocument.parentWindow.execscript("function alert(str){return true;} ", "javascript");//弹出提示
//下面是你的执行操作代码
}

我的不是这样弄的，虽然代码一样，但是我是在执行具体任务的时候，才会写入这个，然后执行这段代码＋我自己的点击代码。

刚才在网上找了下，还有另一种治本的方法呵，高人到处都是。下面是代码，是继承的webBrowser然后屏弊了ShowMessage

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace Test
{

public class MyWebBrowser : System.Windows.Forms.WebBrowser
{
#region ExtendedWebBrowserSite
class ExtendedWebBrowserSite : WebBrowser.WebBrowserSite, UnsafeNativeMethods.IDocHostShowUI
{
public ExtendedWebBrowserSite(WebBrowser host)
: base(host)
{
}

void UnsafeNativeMethods.IDocHostShowUI.ShowMessage(ref UnsafeNativeMethods._RemotableHandle hwnd, string lpstrText, string lpstrCaption, uint dwType, string lpstrHelpFile, uint dwHelpContext, out int plResult)
{
plResult = 0;
//TODO:自定义
}
void UnsafeNativeMethods.IDocHostShowUI.ShowHelp(ref UnsafeNativeMethods._RemotableHandle hwnd, string pszHelpFile, uint uCommand, uint dwData, UnsafeNativeMethods.tagPOINT ptMouse, object pDispatchObjectHit)
{
//TODO:自定义
}
}

protected override WebBrowserSiteBase createWebBrowserSiteBase()
{
return new ExtendedWebBrowserSite(this);
}
#endregion
}

public class UnsafeNativeMethods
{
#region IDocHostShowUI
[StructLayout(LayoutKind.Explicit, Pack = 4)]
public struct __MIDL_IWinTypes_0009
{
// Fields
[FieldOffset(0)]
public int hInproc;
[FieldOffset(0)]
public int hRemote;
}

[StructLayout(LayoutKind.Sequential, Pack = 4)]
public struct _RemotableHandle
{
public int fContext;
public __MIDL_IWinTypes_0009 u;
}

[StructLayout(LayoutKind.Sequential, Pack = 4)]
public struct tagPOINT
{
public int x;
public int y;
}

[ComImport, Guid("C4D244B0-D43E-11CF-893B-00AA00BDCE1A"), InterfaceType((short)1)]
public interface IDocHostShowUI
{
[MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
void ShowMessage([In, ComAliasName("ExtendedWebBrowser2.UnsafeNativeMethods.wireHWND")] ref _RemotableHandle hwnd, [In, MarshalAs(UnmanagedType.LPWStr)] string lpstrText, [In, MarshalAs(UnmanagedType.LPWStr)] string lpstrCaption, [In] uint dwType, [In, MarshalAs(UnmanagedType.LPWStr)] string lpstrHelpFile, [In] uint dwHelpContext, [ComAliasName("ExtendedWebBrowser2.UnsafeNativeMethods.LONG_PTR")] out int plResult);
[MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
void ShowHelp([In, ComAliasName("ExtendedWebBrowser2.UnsafeNativeMethods.wireHWND")] ref _RemotableHandle hwnd, [In, MarshalAs(UnmanagedType.LPWStr)] string pszHelpFile, [In] uint uCommand, [In] uint dwData, [In] tagPOINT ptMouse, [Out, MarshalAs(UnmanagedType.IDispatch)] object pDispatchObjectHit);
}
#endregion

}
}
这个是直接复制过来的啊，这编辑器没有代码功能，汗。。。有点乱。但很好的屏弊webBrowser里的alert,confirm了。

不管怎么样，有二种方法，可以实现webBrowser屏弊alert了。