一.KeyPress事件

private void txt_loopNum_KeyPress(object sender, KeyPressEventArgs e)        {            CheckNum(sender, e);        }

二.CheckNum方法

public void CheckNum(object sender, KeyPressEventArgs e)        {            //阻止从键盘输入键            e.Handled = true;            if (e.KeyChar >= '0' && e.KeyChar <= '9' || (e.KeyChar == (char)8))            {                if (e.KeyChar == (char)8)                {                    e.Handled = false; return;                }                else                {                    int len_lookNum = ((TextEdit)sender).Text.Trim().Length;                    if (len_lookNum < 8)                    {                        if (len_lookNum == 0 && e.KeyChar != '0')                        {                            e.Handled = false; return;                        }                        else if (len_lookNum== 0)                        {                            e.Handled = true; return;                        }                        e.Handled = false; return;                    }                    else                    {                        MessageBox.Show("输入数字过大");                    }                }            }        }