Validating a data entry form before submitting it to the server is one of the most common task in web applications. In ASP.NET Core you can easily do that with the help of validation attributes and tag helpers. However, at times you need to take charge of the client side validation process and roll out your own strategy to validate the data being submitted to the server. For example, you might be building a SPA and want to validate data using HTML5 features. To that end this article discusses how HTML5 form validation features can be used in TypeScript and ASP.NET Core.