通过扩展 WebBrowser 使其有处理错误的能力

MyWebBrowser.cs

using System;
using System.Runtime.InteropServices;
using System.Security.Permissions;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
	public class MyWebBrowser : WebBrowser
	{
		private AxHost.ConnectionPointCookie cookie;
		private MyWebBrowserEventHelper helper;

		public delegate void WebBrowserNavigateErrorEventHandler(object sender, WebBrowserNavigateErrorEventArgs e);

		/// <summary>
		/// 在 <see cref="MyWebBrowser"/> 导航发生错误时触发此事件。
		/// </summary>
		public event WebBrowserNavigateErrorEventHandler NavigateError;

		[PermissionSetAttribute( SecurityAction.LinkDemand, Name = "FullTrust" )]
		protected override void CreateSink()
		{
			base.CreateSink();
			// Create an instance of the client that will handle the event
			// and associate it with the underlying ActiveX control.
			helper = new MyWebBrowserEventHelper( this );
			cookie = new AxHost.ConnectionPointCookie( this.ActiveXInstance, helper, typeof( DWebBrowserEvents2 ) );
		}

		[PermissionSetAttribute( SecurityAction.LinkDemand, Name = "FullTrust" )]
		protected override void DetachSink()
		{
			// Disconnect the client that handles the event
			// from the underlying ActiveX control.
			if ( cookie != null )
			{
				cookie.Disconnect();
				cookie = null;
			}
			base.DetachSink();
		}

		// Raises the NavigateError event.
		protected virtual void OnNavigateError(WebBrowserNavigateErrorEventArgs e)
		{
			if ( this.NavigateError != null )
			{
				this.NavigateError( this, e );
			}
		}

		// Handles the NavigateError event from the underlying ActiveX 
		// control by raising the NavigateError event defined in this class.
		private class MyWebBrowserEventHelper : StandardOleMarshalObject, DWebBrowserEvents2
		{
			private readonly MyWebBrowser parent;

			public MyWebBrowserEventHelper(MyWebBrowser parent)
			{
				this.parent = parent;
			}

			public void NavigateError(object pDisp, ref object url, ref object frame, ref object statusCode, ref bool cancel)
			{
				// Raise the NavigateError event.
				this.parent.OnNavigateError(new WebBrowserNavigateErrorEventArgs((String)url, (String)frame, (Int32)statusCode, cancel ) );
			}
		}
	}

	public class WebBrowserNavigateErrorEventArgs : EventArgs
	{
		public WebBrowserNavigateErrorEventArgs(String url, String frame, Int32 statusCode, Boolean cancel)
		{
			Url = url;
			Frame = frame;
			StatusCode = statusCode;
			Cancel = cancel;
		}

		/// <summary>
		/// 获取或设置请求 URL 。
		/// </summary>
		public string Url { get; set; }

		public string Frame { get; set; }

		/// <summary>
		/// 获取或设置 HTTP 状态码。
		/// </summary>
		public int StatusCode { get; set; }

		/// <summary>
		/// 获取或设置是否取消请求。
		/// </summary>
		public bool Cancel { get; set; }
	}

	[ComImport, Guid( "34A715A0-6587-11D0-924A-0020AFC7AC4D" ), InterfaceType( ComInterfaceType.InterfaceIsIDispatch ), TypeLibType( TypeLibTypeFlags.FHidden )]
	public interface DWebBrowserEvents2
	{
		[DispId( 271 )]
		void NavigateError(
			[In, MarshalAs( UnmanagedType.IDispatch )] object pDisp,
			[In] ref object URL, [In] ref object frame,
			[In] ref object statusCode, [In, Out] ref bool cancel
		);
	}
}

// 调用示例
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
	public partial class Form1 : Form
	{
		public Form1()
		{
			InitializeComponent();
		}

		private void Form1_Load(object sender, EventArgs e)
		{
			this.myWebBrowser1.NavigateError += browser_NavigateError;
		}

		void browser_NavigateError(object sender, WebBrowserNavigateErrorEventArgs e)
		{
			e.Cancel = true;
			MessageBox.Show(e.StatusCode+"");
		}

		private void button1_Click(object sender, EventArgs e)
		{
			this.myWebBrowser1.Navigate(this.textBox1.Text);
		}
	}
}