In this article I will explain with an example, how to add (apply) CSS Class (Styles) in Html.ValidationMessageFor Helper method in ASP.Net MVC Razor.
The Html.ValidationMessageFor Helper method has a parameter named htmlAttributes which is used for adding (applying) CSS Class (Styles) to the displayed validation message.
Configuring Bundles and enabling Client Side validations
Note: By default, the validation done using Data Annotation attributes is Server Side. And hence to make it work Client Side, the Client Side validation must be enabled.
Model
The following Model class consists of one property Name. The property is decorated with the following Data Annotation attributes for performing validations.
1. Required Data Annotation attribute.
Note: The Data Annotations attributes can be used with the Entity Data Model (EDM), LINQ to SQL, and other data models.
The Required Data Annotation has been specified with a property Error Message with a string value. As the name suggests, this string value will be displayed to the user when the validation fails.
using System.ComponentModel.DataAnnotations;
namespace TextBox_Validation_MVC.Models
{
public class PersonModel
{
[Required(ErrorMessage = "Name is required.")]
public string Name { get; set; }
}
}
Controller
The Controller consists of following two Action methods.
Action method for handling GET operation
Inside this Action method, simply the View is returned.
Action method for handling POST operation
This action method handles the POST operation and when the form is submitted, the object of the PersonModel class is sent to this method.
public class HomeController : Controller
{
// GET: Home
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Index(PersonModel person)
{
return View();
}
}
View
Inside the View, in the very first line the PersonModel class is declared as Model for the View.
The View consists of an HTML Form which has been created using the Html.BeginForm method with the following parameters.
ActionName – Name of the Action. In this case the name is Index.
ControllerName – Name of the Controller. In this case the name is Home.
FormMethod – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
The Form consists of the following there HTML Helper functions:-
1. Html.DisplayFor – Displaying the Model property name.
2. Html.TextBoxFor – Creating a TextBox for the Model property.
3. Html.ValidationMessageFor – Displaying the Validation message for the property.
There is also Submit button which when clicked, the Form gets submitted.
Enabling Client-Side validations
By default, the validations performed using Data Annotations and Model class is performed on Server Side.
In order to enable Client-Side validations, you will need to render the following script bundles at the end of the Model using the Scripts.Render function.
1. jQuery
2. jQuery Validation
Once, the above files are rendered automatically, the Client-Side validations using Data Annotations is enabled.
@model TextBox_Validation_MVC.Models.PersonModel
@{
Layout = null;
}
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>Index</title>
<style type="text/css">
body { font-family: Arial; font-size: 10pt; }
.error { color: red; }
</style>
</head>
<body>
@using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
<table>
<tr>
<td>@Html.DisplayFor(m => m.Name)</td>
<td>@Html.TextBoxFor(m => m.Name)</td>
<td>@Html.ValidationMessageFor(m => m.Name, "", new { @class = "error" })</td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="Submit" /></td>
<td></td>
</tr>
</table>
}
</body>
@Scripts.Render("~/bundles/jquery")
@Scripts.Render("~/bundles/jqueryval")
</html>
Screenshot
![ASP.Net MVC: Add (Apply) CSS Class (Styles) in Html.ValidationMessageFor method]()
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