implement validation in asp.net mvc

To implement validation in ASP.NET MVC, you can follow these steps:

1. Create a model class with the properties you want to validate. For example:

public class Person {
   public int Id { get; set; }
   [Required]
   public string Name { get; set; }
   [Range(0, 120)]
   public int Age { get; set; }
}

2. In your controller, add a [HttpPost] action method to handle form submissions. This method should accept an instance of your model as a parameter. For example:

[HttpPost]
public ActionResult Create(Person person) {
   if (ModelState.IsValid) {
      // Save person to database
      return RedirectToAction("Index");
   }
   return View(person);
}

3. In your view, add validation messages to display errors to the user. For example:

@model Person
@using (Html.BeginForm()) {
   @Html.LabelFor(m => m.Name)
   @Html.TextBoxFor(m => m.Name)
   @Html.ValidationMessageFor(m => m.Name)
   
   @Html.LabelFor(m => m.Age)
   @Html.TextBoxFor(m => m.Age)
   @Html.ValidationMessageFor(m => m.Age)
   
   <input type="submit" value="Save" />
}

4. In your Web.config file, make sure the clientValidationEnabled and unobtrusiveJavaScriptEnabled settings are set to true. For example:

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

These steps will enable client-side and server-side validation for your ASP.NET MVC application. If the model validation fails, the validation messages will be displayed to the user, and the form will not be submitted.