Validating user input with c
The cancel button has a Causes Validation property. As we mentioned in the beginning of the article, validation can occur twice: once on the client’s machine and once on the server. Client side validation provides quick feedback for the user.
For this first example we do not need to place much code into the code-behind file. NET runtime does not waste time processing a request with invalid information.
Drag one Text Box control and give it an ID of First Name Text Box, two Button controls (Submit Button and Cancel Button), and one Required Field Validator (First Name Required Field Validator). The following screen shows the form in action, and the user has pressed the Submit button without entering any text into the textbox. The Required Field Validator fails when the value in the associated control matches the value of the Initial Value property of the Required Field Validator.
This Required Field Validator forces the user to enter text into the control associated with the validator. If you want to make sure the user changes a default value placed into the control, set the control’s Text value and the Initial Value property of the Required Field Validator to the same value.
Before accepting data from over the network you need to ensure all of the required fields have been filled out and conform to your formats and business rules. NET provides a number of validation controls to ease the burden of performing validation on both sides of the network. To walk along with the example, create a new web application in Visual Studio . Once the application is setup, right click on the empty web form, select Properties from the context menu, and change the Page Layout property to Flow Layout. Notice we need to check the Is Valid property of the base class before performing any critical action in the submit event.
Place four controls from the Web forms section of the Toolbox onto the form. If Is Valid returns a value of true then all of the validation checks were successful.
Simply put, never trust the data in an incoming request, and always validate on the server.