In this article I will explain with an example, how to perform Decimal TextBox validation i.e. Decimal Number with maximum up to two decimal places validation on Client Side using Data Annotations in ASP.Net MVC.
The Decimal TextBox validation i.e. Decimal Number with maximum up to two decimal places validation will be performed using Regular Expression (Regex).
Note: For beginners in ASP.Net MVC, please refer my article ASP.Net MVC Hello World Tutorial with Sample Program example.
 
 

Model

The following Model class consists of one property Expenses. The property is decorated with the following Data Annotation attributes for performing validations.
1. Required Data Annotation attribute.
2. RegularExpression Data Annotation attribute.
Note: The Data Annotations attribute can be used with the Entity Data Model (EDM), LINQ to SQL, and other data models.
 
The Required Data Annotation and the RegularExpression Data Annotation attributes have been specified with a property ErrorMessage with a string value. As the name suggests, this string value will be displayed to the user when the respective validation fails.
The RegularExpression Data Annotation attribute has been set with a Regular Expression for validating Decimal Number with maximum 2 decimal places.
Valid example: 1.02
using System.ComponentModel.DataAnnotations;
 
namespace Decimal_Validation_MVC.Models
{
    public class PersonModel
    {
        [Display(Name = "Expenses:")]
        [Required(ErrorMessage = "Expenses is required.")]
        [RegularExpression("^[0-9]+(\.[0-9]{1,2})$", ErrorMessage = "Valid Decimal number with maximum 2 decimal places.")]
        public string Expenses { get; set; }
    }
}
 
 

Controller

The Controller consists of following 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 state of the submitted Model is checked using ModelState.IsValid property.
Note: ModelState.IsValid property is an inbuilt property which verifies two things:
         1. Whether the Form values are bound to the Model.
         2. All the validations specified inside Model class using Data annotations have been passed.
 
Finally, the View is returned to Index View.
public class HomeController : Controller
{
    // GET: Home
    public ActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public ActionResult Validate()
    {
        if (ModelState.IsValid)
        {
            // Validation success.
        }
 
        return View("Index");
    }
}
 
 

View

HTML Markup

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 Validate.
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 a following HTML Helper functions:
1. Html.LabelFor – For displaying the Model property name.
2. Html.TextBoxFor – For creating a TextBox for the Model property.
3. Html.ValidationMessageFor – For displaying the Validation message for the property.
 

Submitting the Form

There is also a Submit Button which when clicked, the Form gets submitted and the Expenses value is sent to the Controller.
 

Enabling Client-Side validations

By default, the validations using Data Annotations and Model class is performed on Server Side.
In order to enable Client-Side validations, you will need to inherit the following script files.
1. jquery.min.js
2. jquery.validate.js
3. jquery.validate.unobtrusive.js
Once, the above files are inherited automatically, the Client-Side validations using Data Annotations is enabled.
@model Decimal_Validation_MVC.Models.PersonModel
 
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width"/>
    <title>Index</title>
</head>
<body>
    @using (Html.BeginForm("Validate", "Home", FormMethod.Post))
    {
        <table>
            <tr>
                <td>@Html.LabelFor(m => m.Expenses)</td>
                <td>@Html.TextBoxFor(m => m.Expenses)</td>
                <td>@Html.ValidationMessageFor(m => m.Expenses, "", new { @class = "error" })</td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Submit"/></td>
                <td></td>
            </tr>
        </table>
    }
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.19.3/jquery.validate.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validation-unobtrusive/3.2.12/jquery.validate.unobtrusive.js"></script>
</body>
</html>
 
 

Screenshot

ASP.Net MVC: Decimal TextBox (Decimal number with two places) Validation using Data Annotations
 
 

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