However, the test will be performed in server code.You can control how validation errors are displayed by defining CSS classes that have the following reserved names: .Users get immediate feedback, which is convenient for them.
These pairs let you define rules for both conditions: an error condition and a "normal" (non-error) condition.
It's important to understand that the markup for the error display is always rendered, even if there are no errors.
This test would pass the first time that the page is requested, but not when the request is a form submission.
NET Web Pages and the new Razor syntax provide a fast, approachable, and lightweight way to combine server code with HTML to create dynamic web content.
Therefore, you also have to make sure that the values that users enter can be correctly converted to the appropriate data types.
You might also have certain restrictions on the values.The following example shows how you might validate a value that's passed in a query string.The code tests that the value is not empty and that it's an integer. code-csharp Main] Notice that the test is performed when the request is not a form submission ().The following example shows a page that illustrates these steps. code-cshtml Main] To see how validation works, run this page and deliberately make mistakes.For example, here's what the page looks like if you forget to enter a course name, if you enter an, and if you enter an invalid date: By default, user input is validated after users submit the page — that is, the validation is performed in server code.In particular, data-type validation (integer, date, and so on) don't run on the client.