В WebForms для режима UnobtrusiveValidationMode требуется сопоставление ScriptResourceMapping для "jquery". Добавьте сопоставление ScriptResourceMapping с именем jquery (с учетом регистра).

Message in Russian (Русский)

Unlocalized message

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

Search by Google

Available localized messages

Arabic (العربية) Czech (Čeština) Danish (Dansk) Dutch (Nederlands) Finnish (suomi) French (Français) German (Deutsch) Greek (Ελληνικά) Prior (Message) Hebrew (עברית) Hungarian (magyar) Portuguese (Brazil) (Português (Brasil)) Italian (Italiano) Japanese (日本語) Korean (한국어) Norwegian (Bokmal) (Norsk (Bokmål)) Next (Message) Polish (Polski) Spanish (Español) Swedish (Svenska) Turkish (Türkçe) Chinese (Simplified) (中文(简体)) Chinese (Traditional) (中文（繁體）)