Validators / Controls will be executed always even a condition is false - asp.net

Question

I'm experienced in developing with ASP.NET MVC but have to deal with a lagacy web application with web forms.
I have an html form and inside, there are several input fields and validators (<asp:TextBox />, <asp:CustomValidator />, <ajax:MaskedEditValidator />).
The second part of the form should only be rendered / visible if a condition resolves to true. Also the associated validators inside this block should only validate if a given condition resolves to true. For this I wrapped the respective part in a condition block:
<%
if (condition)
{
%>
...
<ajax:MaskedEditExtender runat="server" ID="meePreisProGruppe" TargetControlID="PreisProGruppeInsertTextBox"
Mask="999" MessageValidatorTip="true" OnFocusCssClass="MaskedEditFocus"
OnInvalidCssClass="MaskedEditError" MaskType="Number" InputDirection="RightToLeft"
AutoComplete="false" ErrorTooltipEnabled="True" />
<ajax:MaskedEditValidator ID="mevPreisProGruppe" runat="server" ValidationGroup="vgBuchungsanfrageMP"
ControlExtender="meePreisProGruppe" ControlToValidate="PreisProGruppeInsertTextBox" IsValidEmpty="false"
InvalidValueMessage="Preis p.Gruppe ungültig" emptyvaluemessage="Preis p.Gruppe fehlt" EmptyValueBlurredText='<img src="/bsb/img/srf/icon_exclamation_error.gif">'
InvalidValueBlurredMessage='<img src="/bsb/img/srf/icon_exclamation_error.gif">'
Display="Dynamic" />
...
<asp:CustomValidator ID="cvRechnungsadresse" Display="Dynamic" ErrorMessage="Rechnungsadresse nicht vollständig!"
OnServerValidate="ServerValidationRechnungsadresse" ValidationGroup="vgBuchungsanfrageMP"
runat="server" />
...
<%
}
%>
With this, the controls do not get rendered, this is what I want. But all the validators will be executed independent to what the condition resolve, though.
How can I solve this issue?

Answer 1

My answer below is based on the assumption that the condition for validators to evaluate is different from the condition for the input control/validators to be rendered.
There is a standard JavaScript function called ValidatorValidate when you use validation in web forms. You need to override this using sample code like below to implement your requirement.
An important point to keep in mind with this solution is to place the code below just before the closing body tag so the function being overridden has been already loaded in browser else you might get a JavaScript error saying that window.ValidatorValidate is undefined.
Also, implement same requirement on server-side using the C# code below, since validators are evaluated on client-side as well as server-side.
Override ValidatorValidate function in JavaScript
<script type="text/javascript">
//create a condition in JavaScript for your validators to validate
//make condition a global variable, like here ( don't set it inside a function)
var condition = ...; //write your condition code on right side of equal operator
//populate this array with client ID's of all validators for which you want to conditionally validate
var conditionalValidatorIds = [];
conditionalValidatorIds.push("<%= validator1.CleintID%>";
conditionalValidatorIds.push("<%= validator2.CleintID%>";
conditionalValidatorIds.push("<%= validator5.CleintID%>";
//now override the standard ValidatorValidate function
var originalValidatorValidate = window.ValidatorValidate;
window.ValidatorValidate = function (val, validationGroup, event) {
//check if the condition is true and if yes then skip this function for all
//validators within the conditionalValidatorIds array
if(condition === true) {
for(var i=0; i < conditionalValidatorIds.length; i++) {
if( val.id === conditionalValidatorIds[i] ) {
val.isvalid = true;
ValidatorUpdateDisplay(val);
return;
}
}
}
//perform original validation when condition is false
window.originalValidatorValidate(val, validationGroup, event);
}
</script>
C# code to override validators evaluation on server-side
public override void Validate(string validationGroup)
{
//you will need to define yourCondition on server-side
bool enableValidators = (someCondition === true);
//then enable/disable your validators based on above condition
validator1.Enabled = enableValidators;
validator2.Enabled = enableValidators
validator3.Enabled = enableValidators;
base.Validate(validationGroup);
}
Another option instead of using above approach is to define only custom validators ( no standard validators like requiredfieldvalidator or comparevalidator etc.) within the if condition block and then within each custom validator client-side function, just check for the condition and if its true then set args.IsValid = true; in it. Do the same on server-side events you have for these custom validators.