HTML helpers are server-side methods that generate HTML for you. We can generate the same form using HTML helpers as follows (HTML.BeginForm, @Html.Label, and @Html.TextBox generate the HTML form element, label, and textbox elements, respectively):

@using (Html.BeginForm())
 {
   <table>        
     <tr> 
       <td>@Html.Label("Name")</td>
       <td>@Html.TextBox("txtName")</td>
     </tr>
     <tr>
       <td>@Html.Label("Age")</td>
       <td>@Html.TextBox("txtAge")</td>
     </tr>
     <tr>
       <td colspan="2"><input type="submit" value="Submit" /></td>
     </tr> 
   </table>
}

You might wonder why we need to use HTML helpers when we can write the HTML code manually. Things will get more complex when we pass the model from the Controller to the view. Using HTML helpers, we can directly build form elements from Models files so that they will pick the names from the Models that you are using.

For example, let's create a folder called Models and a class called Person. This class will act as a model as shown in the following screenshot:

The Person class is just a POCO (Plain Old C# Object) class and will act as a model. The complete code for this class is as follows:

public class Person
{
  public int PersonId { get; set; }
  public string Name { get; set; }
  public int Age { get; set; }
}

Let's create a new action method called ValidateAge. In this method, we will create an empty Person class and pass the Model to the View. We will also create a dynamic property called Title in ViewBag so that we can display this value in View:

[HttpGet]
public IActionResult ValidateAge()
{
  ViewBag.Title = "Validate Age for voting";
  Person person1 = new Person();
  return View(person1);
}

In the view, create the form using the following HTML Helpers:

@model Chapter4.Models.Person
@using (Html.BeginForm("ValidateAge", "Home", FormMethod.Post))
 {
   <table>
     <tr>
       <td>@Html.LabelFor(Model => Model.Name) </td>
       <td>@Html.TextBoxFor(Model => Model.Name) </td>
     </tr>
     <tr>
       <td>@Html.LabelFor(Model => Model.Age)</td>
       <td>@Html.TextBoxFor(Model => Model.Age)</td>
     </tr>
     <tr>
       <td colspan="2"><input type="submit" value="Submit" /></td>
     </tr>
   </table>
}

In the first line, we are telling the View that we are passing the Model of type Person class. This enables you to use the strong type of Model, that is, when you type Model and a dot, IntelliSense provides you with all the properties of the Person class

In the second line, we are using the overloaded BeginForm HTML helpers which accept three parameters—the action method name, the Controller name, and the Form method.

Simply, when the user submits the form, the information should be passed to the mentioned action of the Controller.

In the LabelFor and TextBox For HTML helpers, we are just passing Model properties (name and age); it automatically queries and gets the Model properties and builds the respective HTML elements. This is one of the primary advantages of using HTML helpers. Without using the HTML helpers, this process might become complex.

Now, let's write the respective POST action method in the same way. In the following POST action method, based on the age entered in the form, we set the dynamic property as Message.

[HttpPost]
public IActionResult ValidateAge(Person person1)
{
  if(person1.Age>=18)
  {
    ViewBag.Message = "You are eligible to Vote!";
  }
  else
  {
    ViewBag.Message = "Sorry.You are not old enough to vote!";
  }
  return View();
}

It is to be noted that both the GET and POST action method refer to the same View —ValidateAge.cshtml. Add the following content to the View just above the form element:

@if(ViewBag.Message!=null)
 {
   <b>@ViewBag.Message</b>
 }

Once the user submits the form, the POST action method sets the dynamic Message property in ViewBag. However, the value of this property will be null when the View is rendered as part of the GET request. If the value is not null, insert the message at the top of the page.

When you run the application, you'll get the following output: