AspNetCore.Docs/aspnetcore/includes/mvc-intro/search3.md

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Now when you submit a search, the URL contains the search query string. Searching will also go to the HttpGet Index action method, even if you have a HttpPost Index method.

The following markup shows the change to the form tag:

<form asp-controller="Movies" asp-action="Index" method="get">

Adding Search by genre

Add the following MovieGenreViewModel class to the Models folder:

[!code-csharp]

The movie-genre view model will contain:

• A list of movies.
• A SelectList containing the list of genres. This allows the user to select a genre from the list.
• MovieGenre, which contains the selected genre.
• SearchString, which contains the text users enter in the search text box.

Replace the Index method in MoviesController.cs with the following code:

[!code-csharp]

The following code is a LINQ query that retrieves all the genres from the database.

[!code-csharp]

The SelectList of genres is created by projecting the distinct genres (we don't want our select list to have duplicate genres).

When the user searches for the item, the search value is retained in the search box. To retain the search value, populate the SearchString property with the search value. The search value is the searchString parameter for the Index controller action.

movieGenreVM.genres = new SelectList(await genreQuery.Distinct().ToListAsync())

Adding search by genre to the Index view

Update Index.cshtml as follows:

[!code-HTML]

Examine the lambda expression used in the following HTML Helper:

@Html.DisplayNameFor(model => model.Movies[0].Title)

In the preceding code, the DisplayNameFor HTML Helper inspects the Title property referenced in the lambda expression to determine the display name. Since the lambda expression is inspected rather than evaluated, you don't receive an access violation when model, model.Movies, or model.Movies[0] are null or empty. When the lambda expression is evaluated (for example, @Html.DisplayFor(modelItem => item.Title)), the model's property values are evaluated.

Test the app by searching by genre, by movie title, and by both.