In this article I will explain with an example, how to perform Mobile Number (Cellphone Number) TextBox validation i.e. exact Ten Numbers (Digits) validations using Data Annotations and RegularExpressions (Regex) on Client Side in ASP.Net MVC Razor.
A Mobile Phone Number (Cellphone Number) is a numeric value with exact ten (10) digits and such validation can be achieved using the RegularExpression Data Annotation attribute in ASP.Net MVC Razor.
 
 
Configuring Bundles and enabling Client Side Validation
Please refer the following article for complete information on how to configure Bundles and enable Client Side validation in ASP.Net MVC project.
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 MobileNumber to which the following validation Data Annotation attributes have been applied.
1. Required Data Annotation attribute.
2. RegularExpression Data Annotation attribute.
The RegularExpression Data Annotation attribute accepts the Regular Expression as first parameter. The Regular expression will allow only Numbers (Digits) and the length will be exact 10 digits.
The Required Data Annotation and the RegularExpression Data Annotation attributes have 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 respective validation fails.
public class PersonModel
{
    [Display(Name = "Mobile Number:")]
    [Required(ErrorMessage = "Mobile Number is required.")]
    [RegularExpression(@"^([0-9]{10})$", ErrorMessage = "Invalid Mobile Number.")]
    public string MobileNumber { get; set; }
}
 
 
Controller
The Controller consists of 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.
Inside the View, the following three HTML Helper functions are used:-
1. Html.LabelFor – 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.
The jQuery and the jQuery Validation script bundles are rendered at the end of the Model using the Scripts.Render function.
@model MobileNumber_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.LabelFor(m => m.MobileNumber)</td>
                <td>@Html.TextBoxFor(m => m.MobileNumber)</td>
                <td>@Html.ValidationMessageFor(m => m.MobileNumber, "", 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
Mobile Number (Cellphone Number) Validation using Data Annotations and RegularExpressions (Regex) in ASP.Net MVC
 
 
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