注册 用户名字的验证````

 protected bool checkzhanhao(string zhanghao)
    ...{
        bool va = true;
        if (zhanghao.Length == 0)
        ...{
            Response.Write("<img src='images/check_error.gif'/>不能为空");    
            va = false;
        } else if(zhanghao.Length<5||zhanghao.Length>25)
        ...{
            Response.Write("<img src='images/check_error.gif'/>用户名长度为5-20个字符，请重新输入用户名");
            va = false;

        }else if(!fIsNumber(zhanghao.Substring(0,1),"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"))
        ...{
            Response.Write("<img src='images/check_error.gif'/>用户名输入错误，请以字母开头");
            va = false;
        } else if (!fIsNumber(zhanghao, "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-"))
        ...{
            Response.Write("<img src='images/check_error.gif'/>用户名应该是数字、字母、下划线、连字符号，不允许出现汉字、空格、点等其他字符，请重新输入用户名！");
             va = false;
        }

        return va;
    }
    protected bool fIsNumber(string vl, string vc)
    ...{
        bool va = false;
        string temp = "";
        if (vl.Length == 0)
        ...{
            va= false;
        }
        else
        ...{
            for (int i = 0; i <vl.Length; i++)
            ...{
                temp = vl.Substring(i,1);
                if (vc.IndexOf(temp, 0) == -1)
                ...{
                    va = false;
                }
                else
                ...{
                    va = true;
                }
            }
        }
        return va;
    }