ASP.NET&C#登录验证

根据下拉选项框的值来选择不同的验证，只验证输入的合法性
 protected void Button1_Click(object sender, EventArgs e)
    {

        if (this.username.Text.Trim().ToString() == "")
        {
            System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '用户名不能为空哟！') ", true);
        }

        if (this.password.Text.Trim().ToString() == "")
        {
            System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '密码不能为空哟！') ", true);
        }

        if (Loginlist.SelectedValue.ToString() == "0")
        {
            //这里验证用户名是否有非法字符
     

        string Illegal_Str = ",|&|+|'|\"|or|%|?|$|(|*|@|!|#|^|(|)";
        string[] newstr = Illegal_Str.Split('|');

        for (int i = 0; i < (newstr.Length - 1); i++)
        {
            if (this.username.Text.IndexOf(newstr[i]) != -1)
            {
             
                 System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '请不要输入非法字符') ", true);
            }

            if (this.password.Text.IndexOf(newstr[i]) != -1)
            {

           System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '请不要输入非法字符') ", true);

            }
        }
              //下面是数据库操作
    System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(),"Message", "alert( '验证成功') ", true);

        }

        else if (this.Loginlist.SelectedValue.ToString() == "1")
        {
            //这里写验证手机号
            string strTel = this.username.Text.Trim().ToString();
            string strExpTel = @"^1(3\d{1}|5[389])\d{8}$";
            Regex k = new Regex(strExpTel);
            Match y = k.Match(strTel);

            if(y.Success)
            {
                System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '手机验证成功') ", true);
            }
            else
            {
                System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '手机验证失败') ", true);
            }
        }
        else
        {
           string strInput=this.username.Text.Trim().ToString();
           string strExp = @"\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*";
// Create a new Regex object.
Regex r = new Regex(strExp);
// Find a single match in the string.
Match m = r.Match(strInput);
if (m.Success)
{
    System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '邮箱验证成功') ", true);

}

else
{
    System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Message", "alert( '邮箱验证失败') ", true);
}

            //这里写验证Email
        }

    }