how to write validation error

Question

Jignesh Kumar · Answer

please refer below one, https://www.c-sharpcorner.com/article/validation-message-and-validation-summary-in-asp-net-mvc/ https://www.tutorialsteacher.com/mvc/htmlhelper-validationmessagefor

Praveen Mishra · Answer

1. Using Validation Controls: ASP.NET provides built-in validation controls that you can use to display validation errors. You can place these controls on your web form and customize their error messages. Some commonly used validation controls include: - RequiredFieldValidator: Ensures that a specific input field is not left empty. - RangeValidator: Checks if the input falls within a specified range of values. - RegularExpressionValidator: Validates the input against a specified regular expression pattern. - CustomValidator: Allows you to define custom validation logic. To display validation errors using these controls, follow these steps: a. Add the required validation control to your web form, specifying the validation logic and error message. b. Set the `ErrorMessage` property of the validation control to the desired error message. c. Associate the validation control with the input control you want to validate using the `ControlToValidate` property. d. When the validation fails, the error message will be displayed automatically. 2. Using ModelState: In ASP.NET MVC, you can use the `ModelState` object to store and display validation errors. This approach allows you to perform server-side validation and display the errors next to the corresponding input fields. Here's an example: [HttpPost] public ActionResult MyAction(MyModel model) { if (!ModelState.IsValid) { return View(model); // Return the view with validation errors } // Perform other actions if the validation passes return RedirectToAction("SuccessAction"); // Redirect to a success page } In your view, you can display validation errors using the `ValidationMessageFor` helper method: @model MyModel @Html.ValidationMessageFor(m => m.PropertyName) Make sure you have included the necessary validation attributes (e.g., `[Required]`, `[Range]`, etc.) on your model properties. 3. Manual Validation: You can manually validate input in your code-behind or controller and add validation errors to the `ModelState` object. This approach gives you more flexibility but requires additional code. Here's an example: [HttpPost] public ActionResult MyAction(string inputValue) { if (string.IsNullOrEmpty(inputValue)) { ModelState.AddModelError("inputValue", "The input value is required."); } if (!ModelState.IsValid) { return View(); // Return the view with validation errors } // Perform other actions if the validation passes return RedirectToAction("SuccessAction"); // Redirect to a success page } In your view, you can display manual validation errors using the `ValidationSummary` helper method: @Html.ValidationSummary() These are some common approaches to writing validation errors in ASP.NET. The specific method you choose depends on your application's architecture and requirements.

how to write validation error

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