Validating user input in a web forms page

Sometimes you have to validate information that doesn't come directly from an HTML form.A typical example is a page where a value is passed in a query string, as in the following example: source, including form-field values, query-string values, and cookie values.The CSS rules that end in to both have the same fixed size.

Performing validation in server code is a security measure, in case users bypass client-based validation.The following page shows how to add client validation features to the example shown earlier. code-cshtml Main] Not all validation checks run on the client.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: .Even if users correctly enter an integer, for example, you might need to make sure that the value falls within a certain range. NOTE] Important Validating user input is also important for security.

When you restrict the values that users can enter in forms, you reduce the chance that someone can enter a value that can compromise the security of your site.This article discusses how to validate information you get from users — that is, to make sure that users enter valid information in HTML forms in an ASP. What you'll learn: If you ask users to enter information in a page — for example, into a form — it's important to make sure that the values that they enter are valid.For example, you don't want to process a form that's missing critical information.For example, if a page has an element as a placeholder for an individual field error, even if there is no error.In some situations, displaying an error message can cause the page to reflow and can cause elements on the page to move around.These pairs let you define rules for both conditions: an error condition and a "normal" (non-error) condition.