Getting Client side validation to work while fixing errors of Unobtrusive Validation in ASP.NET 4.5
Moving to ASP.NET 4.5 the existing validation code stops working with a runtime error of Webform UnobtrusiveValidationMode requires a ScriptResourceMapping for jquery. You can force the old style validation to continue to work with the setting below in the web.config.
<appSettings>
<add key="ValidationSettings:UnobtrusiveValidationMode" value="WebForms" />
</appSettings>
However, what you really want to do enable the new validation scheme. I had a lot of trouble getting the client side JavaScript to do the local validation to work. It still caused the server validation to work, but it didn't the client validation first. I read a bunch of articles and they all seemed to enable the server validation, but the client validation. Then until I followed the details in this article:
https://www.c-sharpcorner.com/UploadFile/cd7c2e/ways-to-fix-the-errors-of-unobtrusive-validation/
The basic gist of it is to install several NuGet packages with the client side libraries and changing script manager to actually use those libraries.