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.This is the exact position the error message will appear if validation fails. This also improves response time on the server because the ASP.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.You could have a button to add a new line of data in the form, and that would not be a submit button, nor would you like it to perform the add action unless the above line is filled.
The complete listing for Web Form1cs is shown below. You can disable any of the validation controls by setting the Enabled property to false.It seems that displaying the error was moving subsequent elements down and pushing my button out from under the cursor.In fact, when I click towards the bottom of the button, it doesn’t move far enough to clear the cursor so it works. @kmsheng’s solution works by stopping the chain before validation and @jkoontz2010’s solution works by stopping the chain before DOM insertion.The associated control is set by right clicking on the validator and selecting Properties from the context menu. The rest of the validation controls provided by ASP.In the Properties dialog box find the Control To Validate property and select First Name Text Box from the drop down list. We can set other properties, such as the Error Message property, and the final ASPX source code should look like the following. NET work in a similar fashion to what we've seen above. If the client's web browser is of executing client side Java Script, the first validation pass occurs on the client.