这是我以前做的一个小例子，你可以看看：
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.IO;
using System.Web;
using System.Net;
using System.Text;

namespace 网页源代码
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Panel panel1;
private System.Windows.Forms.Panel panel2;
private System.Windows.Forms.ListBox listBox1;
private System.Windows.Forms.TextBox textBox1;
private System.Windows.Forms.Button button1;
/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.Container components = null;

public Form1()
{
//
// Windows 窗体设计器支持所必需的
//
InitializeComponent();

//
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
//
}

/// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.panel1 = new System.Windows.Forms.Panel();
this.panel2 = new System.Windows.Forms.Panel();
this.listBox1 = new System.Windows.Forms.ListBox();
this.textBox1 = new System.Windows.Forms.TextBox();
this.button1 = new System.Windows.Forms.Button();
this.panel1.SuspendLayout();
this.panel2.SuspendLayout();
this.SuspendLayout();
//
// panel1
//
this.panel1.BackColor = System.Drawing.Color.Teal;
this.panel1.Controls.Add(this.button1);
this.panel1.Controls.Add(this.textBox1);
this.panel1.Dock = System.Windows.Forms.DockStyle.Top;
this.panel1.Location = new System.Drawing.Point(0, 0);
this.panel1.Name = "panel1";
this.panel1.Size = new System.Drawing.Size(352, 48);
this.panel1.TabIndex = 3;
//
// panel2
//
this.panel2.BackColor = System.Drawing.Color.Turquoise;
this.panel2.Controls.Add(this.listBox1);
this.panel2.Dock = System.Windows.Forms.DockStyle.Fill;
this.panel2.Location = new System.Drawing.Point(0, 48);
this.panel2.Name = "panel2";
this.panel2.Size = new System.Drawing.Size(352, 293);
this.panel2.TabIndex = 4;
//
// listBox1
//
this.listBox1.Dock = System.Windows.Forms.DockStyle.Fill;
this.listBox1.ItemHeight = 12;
this.listBox1.Location = new System.Drawing.Point(0, 0);
this.listBox1.Name = "listBox1";
this.listBox1.Size = new System.Drawing.Size(352, 292);
this.listBox1.TabIndex = 0;
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(8, 16);
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(288, 21);
this.textBox1.TabIndex = 0;
this.textBox1.Text = "Http://";
//
// button1
//
this.button1.Location = new System.Drawing.Point(304, 16);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(40, 23);
this.button1.TabIndex = 1;
this.button1.Text = "确定";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// Form1
//
this.AcceptButton = this.button1;
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(352, 341);
this.Controls.Add(this.panel2);
this.Controls.Add(this.panel1);
this.Name = "Form1";
this.Text = "网页源代码";
this.panel1.ResumeLayout(false);
this.panel2.ResumeLayout(false);
this.ResumeLayout(false);

}
#endregion

/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}

private void button1_Click(object sender, System.EventArgs e)
{
try
{
this.listBox1.Items.Clear();
//向一个服务器发送请求
HttpWebRequest hwr=(HttpWebRequest)WebRequest.Create(this.textBox1.Text );
HttpWebResponse hwp=(HttpWebResponse)hwr.GetResponse();
Stream s=hwp.GetResponseStream();
StreamReader sr=new StreamReader(s,System.Text.Encoding.Default);
while(sr.Peek()>-1)
{
listBox1.Items.Add(sr.ReadLine());
}
sr.Close();
s.Close();
}
catch(Exception ex)
{
if(MessageBox.Show(ex.Message,"错误",MessageBoxButtons.OKCancel)==DialogResult.OK)
{
this.textBox1.Clear();
this.textBox1.Focus();
}
else
{
this.textBox1.Focus();
}
}
}
}
}