HTML Helpers

1. Description

HTML Helpers are methods that render HTML elements from Razor views. ASP.NET Core provides tag helpers (preferred) and legacy HTML helper methods (Html.TextBoxFor, Html.DropDownListFor) for building form inputs and links.

2. Why It Is Important

Helpers keep views concise, reduce repetition, and integrate with model metadata (like validation attributes). They also produce correct name and id attributes needed for model binding.

3. Real-World Examples

• Render an input bound to a model property using Html.TextBoxFor or asp-for tag helper.
• Render validation messages tied to model state.

4. Syntax & Explanation

Legacy HTML helper example (.cshtml):

@model MyApp.Models.Product

@using (Html.BeginForm())
{
    @Html.LabelFor(m => m.Name)
    @Html.TextBoxFor(m => m.Name, new { @class = "form-control" })
    @Html.ValidationMessageFor(m => m.Name)

    <button type="submit">Save</button>
}

Tag helper equivalent (recommended):

@model MyApp.Models.Product

<form asp-action="Create" method="post">
    <label asp-for="Name"></label>
    <input asp-for="Name" class="form-control" />
    <span asp-validation-for="Name" class="text-danger"></span>
    <button type="submit">Save</button>
</form>

Notes:

• Tag helpers (asp-for, asp-action) are HTML-friendly and more readable.
• Helpers integrate with DataAnnotations to produce validation attributes.

5. Use Cases

• Building forms tied to view models.
• Generating links, images, and form elements with correct attributes.
• Working with validation and unobtrusive client-side behavior.

6. Mini Practice Task

1. Create a form for a User model using tag helpers and show validation errors.
2. Use Html.ActionLink to create a link to a Details action for a given id.