Asp net validating a checkboxlist control

Posted by / 05-Feb-2020 15:02

Asp net validating a checkboxlist control

In this article, we will explore how to create a custom validation control in ASP.NET and provide both Server and Client Side Validation for the same.Let us see how we can now perform validation directly on the client side, without a postback. As you observe, we override the On Pre Render method and use the Register Expando Attribute to assign the function name ‘Check If List Checked’ an attribute called ‘evaluationfunction’. This is done to make sure that if the users have turned off javascript on their browsers, then this call passes the control back to the page and allows the rendering to continue by calling base. If Java Script is enabled on your browsers, the validation errors are displayed before the form is posted back to the server.To perform client side validation, you would need to override On Pre Render and create the javascript function using a String Builder object and output it using Page. The javascript function(Check If List Checked) takes one parameter, the validator object and returns ‘true’ if Valid (item in both Radiobuttonlist or Check Box List is checked) and ‘false’ if Invalid (Item in either Radiobuttonlist or Check Box List is not selected). The entire source code of the application can be downloaded from here.You will need to implement the ‘Evaluate Is Valid’ method which returns a Boolean value indicating if the field/control being validated is valid or not.The code for the server side validation will be similar to the following: In the code snippet shown above, we override the Evaluate Is Valid() method.Two error messages are displayed when the form is submitted.

There are 6 Validation Controls included in the ASP. NET 3.5 framework, however with a few shortcomings.However, there are a few shortcomings in these controls. NET provides the framework to create new validation controls.If you would like to create your own validation control, you can do so by deriving a new control from the Base Validator abstract class.This sample will demonstrate that the user should select at least one checkbox and one radiobutton before submitting the form to the server.For this purpose, we will first show how to create a custom validation control to perform server-side validation and then extend the control to support client-side validation too.

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