使用WebAPI的Webforms C＃客户端验证CustomValidator

Question

Basically I want to write my validation logic once and use it on both server and client side.

It seems like http://www.asp.net/web-forms/tutorials/hands-on-labs/whats-new-in-web-forms-in-aspnet-45 would fit the bill, but there does not appear to be support for a plain text input so.....

I am using C# and writing a webforms 4.5 application backed by entity framework 5. What I am looking at is how to provide validation client side and server side without repeating the validation logic.

Say I have a text intput that I want to validate for min length, existence, max length. I could put a custom validator on the form and write some javascript code but then I would have to code something similar in the back end as well.

What seems like a better approach would be to encapsulate the validation logic in the back end and then call that logic via a HTTP GET from JS. That way if I need to change the validation logic I update it once in the code behind and the JS client side would stay the same as its merely calling the same GET.

I have seen various examples relating to MVC / Web One / Web API but cannot see how I can apply this to what I am proposing.

Has anyone got any suggestions? Has this been done before? I don't want to reimplement the wheel if I don't have to.

Answer 1

ASP.NET does this for you! You can use annotations in your model classes, like:

 [Required, StringLength(100), Display(Name = "Name")]
 public string ProductName { get; set; }

See this tutorial: http://www.asp.net/web-forms/tutorials/aspnet-45/getting-started-with-aspnet-45-web-forms/create_the_data_access_layer

There are plenty of annotations you can use, and they will work for client-side validation too. So you only have to "write" the logic once.

If standard annotations are not sufficient, you can declare your own annotations. But then you also have to write a client-side validation. This is indeed problematic. Making GET-Calls to the server for validation is of course possible, but this would not be a "real" client-side validation. In these cases maintaining the logic twice might be the most practical solution.