WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for ‘jquery’. Please add a ScriptResourceMapping named jquery (case-sensitive)

Specifies how ASP.NET globally enables the built-in validator controls to use unobtrusive JavaScript for client-side validation logic.

Type: UnobtrusiveValidationMode

Default value: None

Remarks: If this key value is set to “None” [default], the ASP.NET application will use the pre-4.5 behavior (JavaScript inline in the pages) for client-side validation logic. If this key value is set to“WebForms”, ASP.NET uses HTML5 data-attributes and late bound JavaScript from an added script reference for client-side validation logic.

 <appSettings>
     <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
 </appSettings>