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Validation in MVC is the process of checking that the data submitted by the user is valid. This is done to ensure that the data is correct and that it meets the requirements of the application.

There are two main ways to use validation in MVC:

• Data annotation attributes: Data annotation attributes are attributes that can be applied to properties of a model class to specify validation rules. These attributes are evaluated by the MVC framework when the data is submitted, and any errors are displayed to the user.
• Client-side validation: Client-side validation is validation that is performed by the browser before the data is submitted to the server. This type of validation can be used to improve the user experience by providing feedback to the user about the validity of their input.

Here is an example of how to use data annotation attributes to validate a property in a model class:

C#

public class User
{
  [Required]
  [StringLength(100)]
  public string Name { get; set; }
}

The Required attribute specifies that the Name property must have a value. The StringLength attribute specifies that the Name property must be a string with a maximum length of 100 characters.

When the user submits the data, the MVC framework will evaluate the data annotation attributes and display any errors to the user. For example, if the user leaves the Name property blank, the MVC framework will display an error message to the user.

Here is an example of how to use client-side validation to validate a property in a view:

HTML

<input type="text" name="Name" id="Name" />
<span id="NameError" class="error"></span>

The NameError element is a hidden element that will be displayed if the Name property is invalid. The client-side validation code will check the value of the Name property and display an error message if the value is invalid.

Hi friends,

Today I'm going to describe the use of validation in asp.net MVC. If you have used validation control in ASP.NET, it will be easy for you. So let's start it...

First of all, we should discuss about to validation. Like as :

What is validation?

That is the process of evaluating software during the development process or at the end of the development process to determine whether it satisfies specified business requirements. The validation testing ensures that the product actually meets the client's needs. This can also be defined as to demonstrate that the product fulfills its intended use when deployed on an appropriate environment.

Using the Data Annotation Validator Attributes

If we use the Data Annotations Model Binder, we use validator attributes to perform validation. where System.ComponentModel.DataAnnotations namespace includes the following validator attributes:

1.  Range – Enables you to validate whether the value of a property falls between a specified range of values.
2.  RegularExpression – Enables you to validate whether the value of property matches a specified regular expression pattern.
3.  Required – Enables you to mark a property as required.
4.  StringLength – Enables you to specify a maximum length for a string property.
5.  Validation – The base class for all validator attributes.

 Note : When we need validation are not satisfied by any of the standard validators then you always have the option of creating a custom validator attribute by inheriting a new validator attribute from the base Validation attribute. 

That is the goal of the web form validation is to ensure that the user provided necessary and properly formatted information needed to successfully complete an operation. Into this article, we will go beyond the validation itself and explore different validation and error feedback techniques, methods and approaches.

SERVER-SIDE VALIDATION

Into the server-side validation, information is being sent to the server and validated using one of the server-side languages. Whether the validation fails, the response is then sent back to the client, the page that contains the web form is refreshed and feedback is shown. That method is secure because it will work even if JavaScript is turned off in the browser and it can’t be easily bypassed by malicious users. Through the other hand, users will have to fill in the information without getting a response until they submit the form. It results in a slow response from the server. 

Model.cs

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.ComponentModel.DataAnnotations;

using System.Linq;

using System.Web;



namespace MvcApplication6.Models

{

    public class BookCustomModel

    {

        public int ID { get; set; }



        [DisplayName("Book Name")]

        [Required]

        public string BookName { get; set; }



        [DisplayName("Author Name")]

        [Required]

        public string BookAuthor { get; set; }



        public string BookImage { get; set; }



    }

}

create.cshtml

@model MvcApplication6.Models.BookCustomModel



@{

    Layout = null;

}



<!DOCTYPE html>



<html>

<head>

    <meta name="viewport" content="width=device-width" />

    <title>Create</title>

    <style>

        .field-validation-error {

            color: red;

        }

    </style>

</head>

<body>

    @if (ViewData.ModelState.IsValid)

    {

        if (@ViewBag.Name != null)

        {

        <b>BookName : @ViewBag.BookName<br />

            AuthorName : @ViewBag.AuthorName

        </b>

        }

    }



    @using (Html.BeginForm())

    {



        @Html.ValidationSummary(true)



        <fieldset>

            <legend>Book</legend>



            <div class="editor-label">

                @Html.LabelFor(model => model.BookName)

            </div>

            <div class="editor-field">

                @Html.TextBoxFor(model => model.BookName, new { @class = "form-control" })

                @Html.ValidationMessageFor(model => model.BookName)

            </div>



            <div class="editor-label">

                @Html.LabelFor(model => model.BookAuthor)

            </div>

            <div class="editor-field">

                @Html.TextBoxFor(model => model.BookAuthor, new { @class = "form-control" })

                @Html.ValidationMessageFor(model => model.BookAuthor) 
            </div> 

            @*<div class="editor-label"> 
                @Html.LabelFor(model => model.BookImage) 
            </div> 
            <div class="editor-field"> 
                @Html.TextBoxFor(model => model.BookImage) 
                @Html.ValidationMessageFor(model => model.BookImage) 
            </div>*@ 
            <p> 
                <input type="submit" value="Create" /> 
            </p> 
        </fieldset> 
    } 

    <div> 
        @Html.ActionLink("Back to List", "Index") 
    </div> 
   <script src="~/Scripts/jquery-2.1.0.js"></script> 
    <script src="~/Scripts/jquery.validate.min.js"></script> 
    <script src="~/Scripts/jquery.unobtrusive-ajax.min.js"></script> 
    <script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script> 


</body> 
</html> 

CLIENT-SIDE VALIDATION

Here we know that Server-side validation is enough to have a successful and secure form validation. But, for better user experience, however, you might consider using client-side validation. These type of validation are done on the client using script languages such as JavaScript. Through, the using script languages user’s input can be validated as they type. It means a more responsive, visually rich validation. By the client-side validation, the form never gets submitted if validation fails. The validation is being handled in JavaScript methods that you create (or within frameworks/plugins) and users get immediate feedback if validation fails. 

By the client-side validation, the form never gets submitted if validation fails. The validation is being handled in JavaScript methods that you create (or within frameworks/plugins) and users get immediate feedback if validation fails.

The major drawback of client-side validation is that it relies on JavaScript. Whether the users turn JavaScript off, they can easily bypass the validation. It is why validation should always be implemented on both the client and server. Through combining server-side and client-side methods we can get the best of the two: fast response, more secure validation and better user experience.

Useful resources

Here are some of the frameworks, plugins, and tutorials that might help you easily implement validation in your forms.

•  LiveValidation - Its a small, open-source JavaScript validation library. This enables real-time, rich client validation which can be implemented easily. That is the best way to see its capabilities is to check out the example page.
•  Validanguage - A validation framework that enables rich client-side validation.
•  JavaScript Form Validation - A JavaScript validation framework for creating inline validation. You can configure it through JavaScript code or by using the XML configuration file.
•  UniForm - That is an attempt to standardize form markup (XHTML) and CSS. That can help you style error messages, help text, indicators and so on.
•  jQuery Validation plugin - It is one of the most popular validation plugins. Like expected from jQuery plugin, it enables validation in one line of code, unless we can also customize it. This has only 14 kb approx and is compatible with the version of jQuery 1.3.2.
•  jForm - Other different types of jQuery plugins that let you implement validation easily. Neither only that it performs validation but also has the support for live tips. This is still in the development phase but is worth checking.
•  Dynamic JavaScript Form Validation - Provides easy validation and attractive error messages.
•  jQuery Form Validator - Other numerous jQuery validation plugin that performs live validation. This is fully customizable and supports localization as well.
•  Form field hints with CSS and JavaScript - The useful tutorial on how to create helpful tips using CSS and JavaScript. Demo and source are included.
•  PHP Contact Form with jQuery Validation - This tutorial shows how to implement the validation of a contact form using PHP and JavaScript.
•  jQuery Shows - how to implement both client-side and server-side validation using PHP, MVC, javascript etc.
•  Adding Form Validation to WordPress Comments using jQuery - An interesting tutorial for all WordPress users.