Creating self-closing helpers

Self-closing helpers are helpers that can contain HTML and Razor markup. The built-in @Html.BeginForm() helper is an example of this helper type.

In order to create this type of HTML Helper, we'll need to create a helper class that implements the IDisposable interface. Using the IDisposable interface, we can write the element's closing tags when the object is disposed.

The Bootstrap Alert component is a good candidate for such a helper. To create the helper, we'll have to complete the following steps:

1. Create a new subfolder called Alerts inside the Helpers folder in your project.

2. Open the Enums.cs file and add a new item called AlertStyle:

           public enum AlertStyle 
           { 
               Default, 
               Primary, 
               Success, 
               Info, 
               Warning, 
               Danger 
           } 
   

3. Add a new class file called Alert.cs to the Alerts folder.

4. Add a new private, read-only TextWriter object field to the class called _writer:

           private...