This is a simple example of standard MVC validation provided in the .NET framework.

Create a new MVC application.

Edit the index.cshtml file. Important: for client validation to work, the scripts section must be included. (Defined per default in the _Layout View and the BundleConfig.cs in the App_Start folder)

@model MvcStandardValidation.Models.HomeDataModel

<h2>Validation Test for Standard MVC Validation</h2>

@using (Html.BeginForm("Index", "Home"))
{
     @Html.ValidationSummary(true)
     @Html.AntiForgeryToken() 
    <fieldset>
        <legend>Validation Form</legend>

   
        <div>
            @Html.LabelFor(model => model.ValInt1)
        </div>
        <div>
            @Html.EditorFor(model => model.ValInt1)
            @Html.ValidationMessageFor(model => model.ValInt1)
        </div>

        <div>
            @Html.LabelFor(model => model.ValInt2)
        </div>
        <div>
            @Html.EditorFor(model => model.ValInt2)
            @Html.ValidationMessageFor(model => model.ValInt2)
        </div>

        <div>
            @Html.LabelFor(model => model.ValString1)
        </div>
        <div>
            @Html.EditorFor(model => model.ValString1)
            @Html.ValidationMessageFor(model => model.ValString1)
        </div>

        <div>
            @Html.LabelFor(model => model.ValString2)
        </div>
        <div>
            @Html.EditorFor(model => model.ValString2)
            @Html.ValidationMessageFor(model => model.ValString2)
        </div>
    
    
        <div>
            @Html.LabelFor(model => model.ValDouble1)
        </div>
        <div>
            @Html.EditorFor(model => model.ValDouble1)
            @Html.ValidationMessageFor(model => model.ValDouble1)
        </div>
    
        <div>
            @Html.LabelFor(model => model.ValDouble2)
        </div>
        <div>
            @Html.EditorFor(model => model.ValDouble2)
            @Html.ValidationMessageFor(model => model.ValDouble2)
        </div>
    
        <div>
            @Html.LabelFor(model => model.ValDateTime1)
        </div>
        <div>
            @Html.EditorFor(model => model.ValDateTime1)
            @Html.ValidationMessageFor(model => model.ValDateTime1)
        </div>
    
        <div>
            @Html.LabelFor(model => model.ValDateTime2)
        </div>
        <div>
            @Html.EditorFor(model => model.ValDateTime2)
            @Html.ValidationMessageFor(model => model.ValDateTime2)
        </div>
    

        <p>
            <input type="submit" value="SendToServer"  />
        </p>
    </fieldset>

}
   
@section Scripts {
     @Scripts.Render("~/bundles/jqueryval")
}

Create a Model

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace MvcStandardValidation.Models
{
    public class HomeDataModel
    {
        [Required]
        [Range(5,30)]
        public int ValInt1 { get; set; }

        public int? ValInt2 { get; set; }

        public string ValString1 { get; set; }

        [Required(ErrorMessage = "string2 is required")]
        public string ValString2 { get; set; }

        public double ValDouble1 { get; set; }

        public double? ValDouble2 { get; set; }

        public DateTime ValDateTime1 { get; set; }

        public DateTime? ValDateTime2 { get; set; }
    }
}

Edit the web.config (for client side validation)

<appSettings>
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  </appSettings>

NOTE: The client validation can also be enabled/disabled per view:

@{
    HtmlHelper.ClientValidationEnabled = false;
    HtmlHelper.UnobtrusiveJavaScriptEnabled = false;
}

And here’s what your validation errors look like:

Because client validation is enabled, the model is validated on both the client and the server.

Extending the DataAnnotations Model Validator (Custom Validators)

The quickest way to create a custom validator is extend an existing one. This way client validation is supported without any extra effort.

Create an new Attribute

using System.ComponentModel.DataAnnotations;

namespace MvcEL6Validation.Validators
{
    [System.AttributeUsage(System.AttributeTargets.All, AllowMultiple = false, Inherited = true)]
    public sealed class CustomStringPatternAttribute : RegularExpressionAttribute
    {
        const string RegEx = "[0][0-9a-z]{5,20}";

        public CustomStringPatternAttribute()
            : base(RegEx)
        {
        }
    }
}

Add this to the required model

 [CustomStringPattern]
 public string ValString1 { get; set; }

And extend the provider

using System.Web.Http;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using MvcEL6Validation.Validators;

namespace MvcStandardValidation
{
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(CustomStringPatternAttribute), typeof(RegularExpressionAttributeAdapter));
        }
    }
}

Validation error result:

code: https://github.com/damienbod/MvcStandardValidation.git

Anthony Zigenbine provides a great post for property dependency. I have also included this in the example code as it is a great solution for this problem.

I’ve added his script to the validation bundles

bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include(
                        "~/Scripts/jquery.unobtrusive*",
                        "~/Scripts/jquery.validate*",
                        "~/Scripts/RequiredIfValidation*"));

And the following files:

1. RequiredIfAttribute.cs
2. RequiredIfValidation.js

The model and the view are extended to include the requiredIf validator.

Links
http://anthonyvscode.com/2011/07/14/mvc-3-requiredif-validator-for-multiple-values/

http://blogs.msdn.com/b/simonince/archive/2011/02/04/conditional-validation-in-asp-net-mvc-3.aspx

http://www.codeproject.com/Articles/301022/Creating-Custom-Validation-Attribute-in-MVC-3

http://blog.tomasjansson.com/creating-custom-unobtrusive-file-extension-validation-in-asp-net-mvc-3-and-jquery