Html.ValidationMessageFor Example in ASP.Net MVC 5

Html.ValidationMessageFor is a strongly typed method that is used for display error message for input control if the invalid value entered. You can define Html.ValidationMessageFor as follows:

@Html.ValidationMessageFor(Model Property, "String Message", Html Attribute })

Model Property binds the ValidationMessageFor helper method to a model property.
String Message is used for displaying a custom error message
Html Attribute allows you to insert CSS.

Mostly there are 3 parts of validating a control and displaying a message.

1. Create Rules for model properties in Model class.
2. Validating in Controller
3. Displaying an Error message in View.

using System.ComponentModel.DataAnnotations;

namespace HtmlHelperDemo.Models
{
    public class UserModel
    {
        [Required(ErrorMessage = "Name is Required. It cannot be empty")]
        public string UserName { get; set; }
    }
}

 [HttpPost]
 public ActionResult Index(UserModel um)
 {
     if (ModelState.IsValid)
     {
         return View(um);
     }
     else
     {
         return View();
     }
 }    

@using HtmlHelperDemo.Models
@model UserModel

<h3><code>Html.ValidationMessageFor Example</code></h3>
<br />

@using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
    <strong>Name </strong> @Html.EditorFor(m => m.UserName)
    @Html.ValidationMessageFor(m => m.UserName, "", new { @class = "text-danger" })
    <br /><br />
    <input id="Submit" type="submit" value="submit" />
}

<br /><br />
<strong>User Name:</strong> @Html.DisplayFor(m => m.UserName)<br />

<input class="input-validation-error text-box single-line" 
       data-val="true" 
       data-val-required="Name is Required. It cannot be empty" 
       id="UserName" name="UserName" 
       type="text" 
       value="" />

<span class="field-validation-error text-danger" 
      data-valmsg-for="UserName" 
      data-valmsg-replace="true">Name is Required. It cannot be empty
</span>

In this tutorial, I tried to give you a fundamental knowledge about What is and How to Use Html.ValidationMessageFor in ASP.Net MVC 5. You can learn complete Html Form Validation with an example in ASP.Net MVC 5 here.