protected void button1_Click(object sender, System.EventArgs e)
{ 
   OpenFileDialog openFileDialog1 = new OpenFileDialog();
   openFileDialog1.InitialDirectory = "c:\\" ;
   openFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*" ;//设置打开文件类型
   openFileDialog1.FilterIndex = 2 ;
   openFileDialog1.RestoreDirectory = true ;
   if(openFileDialog1.ShowDialog() == DialogResult.OK)
   {
      if(openFileDialog1.FileName!= "")
      {
        MessageBox.Show("你选择了"+openFileDialog1.FileName);//得到文件路径
      }
   }
}

------解决方案--------------------

 OpenFileDialog ofd = new OpenFileDialog();
           ofd.Title = "打开(Open)";
           ofd.FileName = "";
           ofd.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments
           ofd.Filter = "文本文件(*.txt)|*.txt";
           ofd.ValidateNames = true;    
           ofd.CheckFileExists = true; 
           ofd.CheckPathExists = true;           
         try
           {
               if (ofd.ShowDialog() == DialogResult.OK)
               {
                   StreamReader sr = new StreamReader(ofd.FileName, System.Text.Encoding.Default);
                   this.richTextBox1.Text = sr.ReadToEnd();
               }
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message.ToString());
           }


------解决方案--------------------

OpenFileDialog dlg = new OpenFileDialog();
dlg .Filter = "文本文件(*.txt)|*.txt|所有文件(*.*)|*.*";
if(dlg.ShowDialog() == DialogResult.OK)
{
if(dlg.FileName!= "")
{
MessageBox.Show("文件名："+dlg.FileName + "\n扩展名：" + Path.GetExtension(dlg.FileName);
}
}



------解决方案--------------------
C# code
string path = "controlKeyboard.exe";   //将文件存放在bin目录下
//string path = "D:\\controlKeyboard.exe";  //调用非bin目录下的程序路径
ProcessStartInfo startinfo = new ProcessStartInfo(path);
startinfo.WindowStyle = ProcessWindowStyle.Normal;
Process.Start(startinfo);