在两个文本框上进行验证或输入验证 - ASP.NET Webforms

Question

I have two text-box fields on the Registration page and I am trying to setup either-or type of validation. The validation should kick-in when both the fields are empty, saying you must enter either of A or B fields to be able to register.

I have used custom validator like below, in my code, but it doesn't seem to work. I am looking for a smart way to validate these 2 text-boxes. Server side validations part:when i tested it, the break point never hits the function. Can someone suggest a clean way of doing this.

Please note that for the other controls on the page I have required field validators, I cannot have one here because I should be able to set either or condition for these 2 textboxes.

<div class="form-group">
                            <asp:Label Text="" ID="lblSCGrantNumber" runat="server" AssociatedControlID="txtStateCommGrantNumber">
                                 State Commission Number&nbsp;
                            </asp:Label>
                            <asp:TextBox ID="txtStateCommGrantNumber" runat="server" TextMode="SingleLine" placeholder="State Commission Grant Number" AutoCompleteType="None" class="form-control"></asp:TextBox>
                           <%-- <asp:RequiredFieldValidator Display="Dynamic" ID="rfStateCommGrantNumber" Text="Required" SetFocusOnError="true" CssClass="text-danger" ControlToValidate="txtStateCommGrantNumber" runat="server"></asp:RequiredFieldValidator>--%>
                          <asp:CustomValidator ID="stateCommissionGrants" runat="server" OnServerValidate="ServerValidation" OnClientValidate="Validate_textboxes" ControlToValidate="txtStateCommGrantNumber" ErrorMessage="One of the two fields is required" ValidateEmptyText="true"></asp:CustomValidator>
                        </div>

                           <div class="form-group">
                            <asp:Label Text="" ID="lblGrantNumber" runat="server" AssociatedControlID="txtStateCommGrantNumber">
                                 Grant Number&nbsp;
                            </asp:Label>
                            <asp:TextBox ID="txtGrantNumber" runat="server" TextMode="SingleLine" placeholder="Grant Number" AutoCompleteType="None" class="form-control"></asp:TextBox>
                            <%--<asp:RequiredFieldValidator Display="Dynamic" ID="rfStateCommGrantNumber" Text="Required" SetFocusOnError="true" CssClass="text-danger" ControlToValidate="txtStateCommGrantNumber" runat="server"></asp:RequiredFieldValidator>--%>
                            <asp:CustomValidator ID="grants" runat="server" OnServerValidate="ServerValidation" OnClientValidate="Validate_textboxes" ControlToValidate="txtGrantNumber" ErrorMessage="One of the two is required" ValidateEmptyText="true"></asp:CustomValidator>
                             </div>

Client side code:

<script type="text/javascript">
        (function Validate_textboxes(sender, args) {
            var v = document.getElementById('<%=txtStateCommGrantNumber.ClientID%>').value;
            var v = document.getElementById('<%=txtGrantNumber.ClientID%>').value;
            if (v == '') {
                args.IsValid = false;
            }
            else {

            }


        });

serverside code:

protected void ServerValidation(object source, ServerValidateEventArgs args)
        {
            args.IsValid = txtStateCommGrantNumber.Text.Trim().Length > 0 || txtGrantNumber.Text.Trim().Length > 0;
            if (!args.IsValid)
            {
                CustomValidator customvalidator = new CustomValidator();
                customvalidator.IsValid = false;
                customvalidator.ErrorMessage = "TextBox1 and TexBox2 can't both be empty";
                Page.Form.Controls.Add(customvalidator);
            }
        }

Answer 1

You have to use ClientValidationFunction attribute of CustomValidator control. And within javascript function you have to set args.IsValid property to true or false. For example:

<asp:Textbox id="text1" runat="server" text=""></asp:Textbox>
<asp:Textbox id="text2" runat="server" text=""></asp:Textbox>
<asp:CustomValidator id="CustomValidator1" runat="server" 
  ControlToValidate = "text1"
  ErrorMessage = "Required"
  ClientValidationFunction="validate" >
</asp:CustomValidator>

And Javascript:

<script type="text/javascript">
  function validate(oSrc, args){
            var v1 = document.getElementById('<%=text1.ClientID%>').value;
            var v2 = document.getElementById('<%=text2.ClientID%>').value;
            if (v1 == '' && v2 == '') {
                args.IsValid = false;
            }
            else {
               args.IsValid = true;
            }
}
</script>

Edit: If the textbox is empty it might not trigger the validation event. To overcome this, you can add ValidateEmptyText="true" attribute to custom validator or can use separate required field validator to validate empty values.