Add search to ASP.NET Core Razor Pages

By Rick Anderson

In this document, search capability is added to the Index page that enables searching movies by genre or name.

Update the Index page's OnGetAsync method with the following code:

public async Task OnGetAsync(string searchString)
{
    var movies = from m in _context.Movie
                 select m;

    if (!String.IsNullOrEmpty(searchString))
    {
        movies = movies.Where(s => s.Title.Contains(searchString));
    }

    Movie = await movies.ToListAsync();
}

The first line of the OnGetAsync method creates a LINQ query to select the movies:

// using System.Linq;
var movies = from m in _context.Movie
             select m;

The query is only defined at this point, it has not been run against the database.

If the searchString parameter contains a string, the movies query is modified to filter on the search string:

if (!String.IsNullOrEmpty(searchString))
{
    movies = movies.Where(s => s.Title.Contains(searchString));
}

The s => s.Title.Contains() code is a Lambda Expression. Lambdas are used in method-based LINQ queries as arguments to standard query operator methods such as the Where method or Contains (used in the preceding code). LINQ queries are not executed when they're defined or when they're modified by calling a method (such as Where, Contains or OrderBy). Rather, query execution is deferred. That means the evaluation of an expression is delayed until its realized value is iterated over or the ToListAsync method is called. See Query Execution for more information.

Note: The Contains method is run on the database, not in the C# code. The case sensitivity on the query depends on the database and the collation. On SQL Server, Contains maps to SQL LIKE, which is case insensitive. In SQLite, with the default collation, it's case sensitive.

Navigate to the Movies page and append a query string such as ?searchString=Ghost to the URL (for example, http://localhost:5000/Movies?searchString=Ghost). The filtered movies are displayed.

Index view

If the following route template is added to the Index page, the search string can be passed as a URL segment (for example, http://localhost:5000/Movies/Ghost).

@page "{searchString?}"

The preceding route constraint allows searching the title as route data (a URL segment) instead of as a query string value. The ? in "{searchString?}" means this is an optional route parameter.

Index view with the word ghost added to the Url and a returned movie list of two movies, Ghostbusters and Ghostbusters 2

However, you can't expect users to modify the URL to search for a movie. In this step, UI is added to filter movies. If you added the route constraint "{searchString?}", remove it.

Open the Pages/Movies/Index.cshtml file, and add the <form> markup highlighted in the following code:

@page
@model RazorPagesMovie.Pages.Movies.IndexModel

@{
    ViewData["Title"] = "Index";
}

<h2>Index</h2>

<p>
    <a asp-page="Create">Create New</a>
</p>

<form>
    <p>
        Title: <input type="text" name="SearchString">
        <input type="submit" value="Filter" />
    </p>
</form>

<table class="table">
@*Markup removed for brevity.*@

The HTML <form> tag uses the Form Tag Helper. When the form is submitted, the filter string is sent to the Pages/Movies/Index page. Save the changes and test the filter.

Index view with the word ghost typed into the Title filter textbox

Search by genre

Add the following highlighted properties to Pages/Movies/Index.cshtml.cs:

public class IndexModel : PageModel
{
    private readonly RazorPagesMovie.Models.MovieContext _context;

    public IndexModel(RazorPagesMovie.Models.MovieContext context)
    {
        _context = context;
    }

    public IList<Movie> Movie { get; set; }
    public SelectList Genres { get; set; }
    public string MovieGenre { get; set; }
public class IndexModel : PageModel
{
    private readonly RazorPagesMovie.Models.RazorPagesMovieContext _context;

    public IndexModel(RazorPagesMovie.Models.RazorPagesMovieContext context)
    {
        _context = context;
    }

    public IList<Movie> Movie { get; set; }
    public SelectList Genres { get; set; }
    public string MovieGenre { get; set; }

The Genres property contains the list of genres. This allows the user to select a genre from the list.

The MovieGenre property contains the specific genre the user selects (for example, "Western").

Update the OnGetAsync method with the following code:

// Requires using Microsoft.AspNetCore.Mvc.Rendering;
public async Task OnGetAsync(string movieGenre, string searchString)
{
    // Use LINQ to get list of genres.
    IQueryable<string> genreQuery = from m in _context.Movie
                                    orderby m.Genre
                                    select m.Genre;

    var movies = from m in _context.Movie
                 select m;

    if (!String.IsNullOrEmpty(searchString))
    {
        movies = movies.Where(s => s.Title.Contains(searchString));
    }

    if (!String.IsNullOrEmpty(movieGenre))
    {
        movies = movies.Where(x => x.Genre == movieGenre);
    }
    Genres = new SelectList(await genreQuery.Distinct().ToListAsync());
    Movie = await movies.ToListAsync();
}

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

// Use LINQ to get list of genres.
IQueryable<string> genreQuery = from m in _context.Movie
                                orderby m.Genre
                                select m.Genre;

The SelectList of genres is created by projecting the distinct genres.

Genres = new SelectList(await genreQuery.Distinct().ToListAsync());

Adding search by genre

Update Index.cshtml as follows:

@page
@model RazorPagesMovie.Pages.Movies.IndexModel

@{
    ViewData["Title"] = "Index";
}

<h2>Index</h2>

<p>
    <a asp-page="Create">Create New</a>
</p>

<form>
    <p>
        <select asp-for="MovieGenre" asp-items="Model.Genres">
            <option value="">All</option>
        </select>

        Title: <input type="text" name="SearchString">
        <input type="submit" value="Filter" />
    </p>
</form>

<table class="table">
    <thead>

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