Asp.Net自定义验证控件不显示错误消息

下面的代码用于验证何时点击表单提交按钮，但是我没有得到想要的结果。

它应该显示错误消息，但他们没有被显示我做错了什么?

自定义验证器验证密码，它应该根据发生的错误更改错误消息:

1. 密码为空
2. 密码无效
3. 密码不匹配

一次只能显示一个错误，所以我在. asx .cs中编写了这个自定义验证器:

    protected void cvPasswordValidation_ServerValidate(object source, ServerValidateEventArgs args)
    {
        bool IsPasswordBlank = false;
        bool IsPasswordValid = false;
        cvPasswordValidation.IsValid = false;
        // If password is blank then IsValid is false, show blank password errors.
        if (String.IsNullOrEmpty(args.Value))
        {
            //args.IsValid = false;
            IsPasswordBlank = true;
            //Show blank password error depending on which box is empty.
            if (String.IsNullOrEmpty(txtPassword.Text))
            {
                cvPasswordValidation.ErrorMessage = "You must enter password";
            }
            else
            {
                cvPasswordValidation.ErrorMessage = "You must confirm password";
            }
            cvPasswordValidation.IsValid = false;
        }
        else
        {
            cvPasswordValidation.IsValid = true;
        }
        // If password is not valid format then IsValid is false, show invalid format errors.
        if (!Regex.IsMatch(args.Value, RegexHelper.ValidPassword)) 
        {
            IsPasswordValid = true;
            //Show invalid format errors, if password is not blank
            if (IsPasswordBlank == false)
            {
                cvPasswordValidation.ErrorMessage = "<b>Current password</b> not in correct format. Your password must contain 6 - 12 characters with a combination of numbers and letters.";
            }
            cvPasswordValidation.IsValid = false;
        } 
        else 
        {
            cvPasswordValidation.IsValid = true; 
        } 
        // If passwords do not match then IsValid is false, show do not match errors.
        bool areEqual = String.Equals(txtPassword.Text, txtConfirmPassword.Text, StringComparison.Ordinal);
        if (areEqual == false)
        {
            //Show do not match errors is password is not blank and is not invalid format
            if (IsPasswordBlank == false && IsPasswordValid == false)
            {
                cvPasswordValidation.ErrorMessage = "Your passwords do not match.";
            }
            cvPasswordValidation.IsValid = false;
        }
        else
        {
            cvPasswordValidation.IsValid = true;
        }
    }

和。ascx:

<asp:TextBox runat="server" ID="txtPassword" MaxLength="12" autocomplete="off" TextMode="Password" ValidationGroup="vgOnlineDetails"></asp:TextBox>
<asp:CustomValidator ID="cvPasswordValidation"
                 runat="server"
                 display="Dynamic"
                 OnServerValidate="cvPasswordValidation_ServerValidate"
                 ControlToValidate="txtPassword"
                 ValidationGroup="vgOnlineDetails">
</asp:CustomValidator>