Server side validations are required for validating the user input whether it is correct and valid. If the received input data is valid then we do the further processing with the data.
Introduction
This article will help us to learn how to make use of server side validations using explicit
model validation.you can check my Previous article on Model validation with Data Annotations here.
Lets look into the sample implementation
- Step 1 Lets create the Application as shown in my previous article from here..
A new property Email in Model class is added
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace Serversidevalidation.Models
{
public class Student
{
public string Name { get; set; }
public string Email { get; set; }
}
}- Step 2 Now Lets create a empty controller as shown below
Right click on Controllers Folder-->Add-->Scaffold-->Select MVC5 Controller-Empty -->provide specific name
Now add the below lines to the controller
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Mvc;
namespace Serversidevalidation.Controllers
{
public class StudentController : Controller
{
//
// GET: /Student/
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Index(Serversidevalidation.Models.Student model)
{
if (string.IsNullOrEmpty(model.Name))
{
ModelState.AddModelError("Name", "Name is required");
}
if (!string.IsNullOrEmpty(model.Email))
{
string emailvalidation = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +
@"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +
@".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
Regex re = new Regex(emailvalidation);
if (!re.IsMatch(model.Email))
{
ModelState.AddModelError("Email", "Provide a valid Email");
}
}
else
{
ModelState.AddModelError("Email", "Email is required");
}
if (ModelState.IsValid)
{
ViewBag.Name = model.Name;
ViewBag.Email = model.Email;
}
return View(model);
}
}
}
Here we have used Regular Expression to validate the Email Field and provided the error messages
using System.Text.RegularExpressions is the Namespace which allows us to use the Regular Expressions
- Step 3 Now Lets Create the View for the Model as shown
Right click on Views Folder-->Add-->New Folder-->provide name
Right click on the folder created-->Add-->Scaffold-->MVC5 View-->provide a name-->select Empty Template-- -->select Model class
Lets create the view as shown
@{
ViewBag.Title = "Index";
}
<h2>Index</h2>
@using (Html.BeginForm())
{
if (@ViewData.ModelState.IsValid)
{
if (@ViewBag.Name != null)
{
<b>
Name : @ViewBag.Name<br />
Email : @ViewBag.Email
</b>
}
}
<fieldset>
<legend>Students</legend>
<div class="editor-label">
@Html.LabelFor(model => model.Name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Name)
@if (!ViewData.ModelState.IsValid)
{
<span class="field-validation-error">@ViewData.ModelState["Name"].Errors[0].ErrorMessage</span>
}
</div>
<div class="editor-label">
@Html.LabelFor(model => model.Email)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Email)
@if (!ViewData.ModelState.IsValid)
{
<span class="field-validation-error">@ViewData.ModelState["Email"].Errors[0].ErrorMessage</span>
}
</div>
<p>
<input type="submit" value="Register" />
</p>
</fieldset>
}
Right click on Index.cshtml and view in browser we can watch the following ouput
When no data is given
When wrong Email is provided
Conclusion
In this article we have learned how to add error manually to model state object