正则表达式的使用

        using System.Text.RegularExpressions;        

        private string pattern = @"^[0-9]*$";       

          private void textBox1_TextChanged(object sender, TextChangedEventArgs e)      

         {            

              Match m = Regex.Match(this.textBox1.Text, pattern);          

              if (!m.Success)            

              {               

                    this.textBox1.Text = resultVal;      

                   // this.textBox1.SelectionStart = this.textBox1.Text.Length;      

               }        

              else          

              {              

                   resultVal = this.textBox1.Text;   

              }       

           }