| title | author | description | ms.author | ms.date | uid |
|---|---|---|---|---|---|
Scaffolded Razor Pages in ASP.NET Core |
rick-anderson |
Explains the Razor Pages generated by scaffolding. |
riande |
08/17/2019 |
tutorials/razor-pages/page |
::: moniker range=">= aspnetcore-3.0"
This tutorial examines the Razor Pages created by scaffolding in the previous tutorial.
[!INCLUDEView or download sample code]
Examine the Pages/Movies/Index.cshtml.cs Page Model:
Razor Pages are derived from PageModel. By convention, the PageModel-derived class is called <PageName>Model. The constructor uses dependency injection to add the RazorPagesMovieContext to the page. All the scaffolded pages follow this pattern. See Asynchronous code for more information on asynchronous programming with Entity Framework.
When a request is made for the page, the OnGetAsync method returns a list of movies to the Razor Page. OnGetAsync or OnGet is called to initialize the state of the page. In this case, OnGetAsync gets a list of movies and displays them.
When OnGet returns void or OnGetAsync returnsTask, no return statement is used. When the return type is IActionResult or Task<IActionResult>, a return statement must be provided. For example, the Pages/Movies/Create.cshtml.cs OnPostAsync method:
Examine the Pages/Movies/Index.cshtml Razor Page:
Razor can transition from HTML into C# or into Razor-specific markup. When an @ symbol is followed by a Razor reserved keyword, it transitions into Razor-specific markup, otherwise it transitions into C#.
The @page Razor directive makes the file an MVC action, which means that it can handle requests. @page must be the first Razor directive on a page. @page is an example of transitioning into Razor-specific markup. See Razor syntax for more information.
Examine the lambda expression used in the following HTML Helper:
@Html.DisplayNameFor(model => model.Movie[0].Title)The DisplayNameFor HTML Helper inspects the Title property referenced in the lambda expression to determine the display name. The lambda expression is inspected rather than evaluated. That means there is no access violation when model, model.Movie, or model.Movie[0] is null or empty. When the lambda expression is evaluated (for example, with @Html.DisplayFor(modelItem => item.Title)), the model's property values are evaluated.
The @model directive specifies the type of the model passed to the Razor Page. In the preceding example, the @model line makes the PageModel-derived class available to the Razor Page. The model is used in the @Html.DisplayNameFor and @Html.DisplayFor HTML Helpers on the page.
Select the menu links (RazorPagesMovie, Home, and Privacy). Each page shows the same menu layout. The menu layout is implemented in the Pages/Shared/_Layout.cshtml file. Open the Pages/Shared/_Layout.cshtml file.
Layout templates allow the HTML container layout to be:
- Specified in one place.
- Applied in multiple pages in the site.
Find the @RenderBody() line. RenderBody is a placeholder where all the page-specific views show up, wrapped in the layout page. For example, select the Privacy link and the Pages/Privacy.cshtml view is rendered inside the RenderBody method.
Consider the following markup from the Pages/Movies/Index.cshtml file:
The preceding highlighted markup is an example of Razor transitioning into C#. The { and } characters enclose a block of C# code.
The PageModel base class contains a ViewData dictionary property that can be used to pass data to a View. Objects are added to the ViewData dictionary using a key/value pattern. In the preceding sample, the "Title" property is added to the ViewData dictionary.
The "Title" property is used in the Pages/Shared/_Layout.cshtml file. The following markup shows the first few lines of the _Layout.cshtml file.
The line @*Markup removed for brevity.*@ is a Razor comment. Unlike HTML comments (<!-- -->), Razor comments are not sent to the client.
Change the <title> element in the Pages/Shared/_Layout.cshtml file to display Movie rather than RazorPagesMovie.
Find the following anchor element in the Pages/Shared/_Layout.cshtml file.
<a class="navbar-brand" asp-area="" asp-page="/Index">RazorPagesMovie</a>Replace the preceding element with the following markup:
<a class="navbar-brand" asp-page="/Movies/Index">RpMovie</a>The preceding anchor element is a Tag Helper. In this case, it's the Anchor Tag Helper. The asp-page="/Movies/Index" Tag Helper attribute and value creates a link to the /Movies/Index Razor Page. The asp-area attribute value is empty, so the area isn't used in the link. See Areas for more information.
Save your changes, and test the app by clicking on the RpMovie link. See the _Layout.cshtml file in GitHub if you have any problems.
Test the other links (Home, RpMovie, Create, Edit, and Delete). Each page sets the title, which you can see in the browser tab. When you bookmark a page, the title is used for the bookmark.
Note
You may not be able to enter decimal commas in the Price field. To support jQuery validation for non-English locales that use a comma (",") for a decimal point, and non US-English date formats, you must take steps to globalize your app. See this GitHub issue 4076 for instructions on adding decimal comma.
The Layout property is set in the Pages/_ViewStart.cshtml file:
The preceding markup sets the layout file to Pages/Shared/_Layout.cshtml for all Razor files under the Pages folder. See Layout for more information.
Examine the Pages/Movies/Create.cshtml.cs page model:
The OnGet method initializes any state needed for the page. The Create page doesn't have any state to initialize, so Page is returned. Later in the tutorial, an example of OnGet initializing state is shown. The Page method creates a PageResult object that renders the Create.cshtml page.
The Movie property uses the [BindProperty] attribute to opt-in to model binding. When the Create form posts the form values, the ASP.NET Core runtime binds the posted values to the Movie model.
The OnPostAsync method is run when the page posts form data:
If there are any model errors, the form is redisplayed, along with any form data posted. Most model errors can be caught on the client-side before the form is posted. An example of a model error is posting a value for the date field that cannot be converted to a date. Client-side validation and model validation are discussed later in the tutorial.
If there are no model errors, the data is saved, and the browser is redirected to the Index page.
Examine the Pages/Movies/Create.cshtml Razor Page file:
Visual Studio displays the following tags in a distinctive bold font used for Tag Helpers:
<form method="post"><div asp-validation-summary="ModelOnly" class="text-danger"></div><label asp-for="Movie.Title" class="control-label"></label><input asp-for="Movie.Title" class="form-control" /><span asp-validation-for="Movie.Title" class="text-danger"></span>
The following Tag Helpers are shown in the preceding markup:
<form method="post"><div asp-validation-summary="ModelOnly" class="text-danger"></div><label asp-for="Movie.Title" class="control-label"></label><input asp-for="Movie.Title" class="form-control" /><span asp-validation-for="Movie.Title" class="text-danger"></span>
Visual Studio displays the following tags in a distinctive bold font used for Tag Helpers:
<form method="post"><div asp-validation-summary="ModelOnly" class="text-danger"></div><label asp-for="Movie.Title" class="control-label"></label><input asp-for="Movie.Title" class="form-control" /><span asp-validation-for="Movie.Title" class="text-danger"></span>
The <form method="post"> element is a Form Tag Helper. The Form Tag Helper automatically includes an antiforgery token.
The scaffolding engine creates Razor markup for each field in the model (except the ID) similar to the following:
The Validation Tag Helpers (<div asp-validation-summary and <span asp-validation-for) display validation errors. Validation is covered in more detail later in this series.
The Label Tag Helper (<label asp-for="Movie.Title" class="control-label"></label>) generates the label caption and for attribute for the Title property.
The Input Tag Helper (<input asp-for="Movie.Title" class="form-control">) uses the DataAnnotations attributes and produces HTML attributes needed for jQuery Validation on the client-side.
For more information on Tag Helpers such as <form method="post">, see Tag Helpers in ASP.NET Core.
[!div class="step-by-step"] Previous: Adding a model Next: Database
::: moniker-end
::: moniker range="< aspnetcore-3.0"
This tutorial examines the Razor Pages created by scaffolding in the previous tutorial.
View or download sample.
Examine the Pages/Movies/Index.cshtml.cs Page Model:
Razor Pages are derived from PageModel. By convention, the PageModel-derived class is called <PageName>Model. The constructor uses dependency injection to add the RazorPagesMovieContext to the page. All the scaffolded pages follow this pattern. See Asynchronous code for more information on asynchronous programming with Entity Framework.
When a request is made for the page, the OnGetAsync method returns a list of movies to the Razor Page. OnGetAsync or OnGet is called on a Razor Page to initialize the state for the page. In this case, OnGetAsync gets a list of movies and displays them.
When OnGet returns void or OnGetAsync returnsTask, no return method is used. When the return type is IActionResult or Task<IActionResult>, a return statement must be provided. For example, the Pages/Movies/Create.cshtml.cs OnPostAsync method:
Examine the Pages/Movies/Index.cshtml Razor Page:
Razor can transition from HTML into C# or into Razor-specific markup. When an @ symbol is followed by a Razor reserved keyword, it transitions into Razor-specific markup, otherwise it transitions into C#.
The @page Razor directive makes the file into an MVC action, which means that it can handle requests. @page must be the first Razor directive on a page. @page is an example of transitioning into Razor-specific markup. See Razor syntax for more information.
Examine the lambda expression used in the following HTML Helper:
@Html.DisplayNameFor(model => model.Movie[0].Title)The DisplayNameFor HTML Helper inspects the Title property referenced in the lambda expression to determine the display name. The lambda expression is inspected rather than evaluated. That means there is no access violation when model, model.Movie, or model.Movie[0] are null or empty. When the lambda expression is evaluated (for example, with @Html.DisplayFor(modelItem => item.Title)), the model's property values are evaluated.
The @model directive specifies the type of the model passed to the Razor Page. In the preceding example, the @model line makes the PageModel-derived class available to the Razor Page. The model is used in the @Html.DisplayNameFor and @Html.DisplayFor HTML Helpers on the page.
Select the menu links (RazorPagesMovie, Home, and Privacy). Each page shows the same menu layout. The menu layout is implemented in the Pages/Shared/_Layout.cshtml file. Open the Pages/Shared/_Layout.cshtml file.
Layout templates allow you to specify the HTML container layout of your site in one place and then apply it across multiple pages in your site. Find the @RenderBody() line. RenderBody is a placeholder where all the page-specific views you create show up, wrapped in the layout page. For example, if you select the Privacy link, the Pages/Privacy.cshtml view is rendered inside the RenderBody method.
Consider the following code from the Pages/Movies/Index.cshtml file:
The preceding highlighted code is an example of Razor transitioning into C#. The { and } characters enclose a block of C# code.
The PageModel base class has a ViewData dictionary property that can be used to add data that you want to pass to a View. You add objects into the ViewData dictionary using a key/value pattern. In the preceding sample, the "Title" property is added to the ViewData dictionary.
The "Title" property is used in the Pages/Shared/_Layout.cshtml file. The following markup shows the first few lines of the _Layout.cshtml file.
The line @*Markup removed for brevity.*@ is a Razor comment which doesn't appear in your layout file. Unlike HTML comments (<!-- -->), Razor comments are not sent to the client.
Change the <title> element in the Pages/Shared/_Layout.cshtml file to display Movie rather than RazorPagesMovie.
Find the following anchor element in the Pages/Shared/_Layout.cshtml file.
<a class="navbar-brand" asp-area="" asp-page="/Index">RazorPagesMovie</a>Replace the preceding element with the following markup.
<a class="navbar-brand" asp-page="/Movies/Index">RpMovie</a>The preceding anchor element is a Tag Helper. In this case, it's the Anchor Tag Helper. The asp-page="/Movies/Index" Tag Helper attribute and value creates a link to the /Movies/Index Razor Page. The asp-area attribute value is empty, so the area isn't used in the link. See Areas for more information.
Save your changes, and test the app by clicking on the RpMovie link. See the _Layout.cshtml file in GitHub if you have any problems.
Test the other links (Home, RpMovie, Create, Edit, and Delete). Each page sets the title, which you can see in the browser tab. When you bookmark a page, the title is used for the bookmark.
Note
You may not be able to enter decimal commas in the Price field. To support jQuery validation for non-English locales that use a comma (",") for a decimal point, and non US-English date formats, you must take steps to globalize your app. This GitHub issue 4076 for instructions on adding decimal comma.
The Layout property is set in the Pages/_ViewStart.cshtml file:
The preceding markup sets the layout file to Pages/Shared/_Layout.cshtml for all Razor files under the Pages folder. See Layout for more information.
Examine the Pages/Movies/Create.cshtml.cs page model:
The OnGet method initializes any state needed for the page. The Create page doesn't have any state to initialize, so Page is returned. Later in the tutorial you see OnGet method initialize state. The Page method creates a PageResult object that renders the Create.cshtml page.
The Movie property uses the [BindProperty] attribute to opt-in to model binding. When the Create form posts the form values, the ASP.NET Core runtime binds the posted values to the Movie model.
The OnPostAsync method is run when the page posts form data:
If there are any model errors, the form is redisplayed, along with any form data posted. Most model errors can be caught on the client-side before the form is posted. An example of a model error is posting a value for the date field that cannot be converted to a date. Client-side validation and model validation are discussed later in the tutorial.
If there are no model errors, the data is saved, and the browser is redirected to the Index page.
Examine the Pages/Movies/Create.cshtml Razor Page file:
Visual Studio displays the <form method="post"> tag in a distinctive bold font used for Tag Helpers:
For more information on Tag Helpers such as <form method="post">, see Tag Helpers in ASP.NET Core.
Visual Studio for Mac displays the <form method="post"> tag in a distinctive bold font used for Tag Helpers.
The <form method="post"> element is a Form Tag Helper. The Form Tag Helper automatically includes an antiforgery token.
The scaffolding engine creates Razor markup for each field in the model (except the ID) similar to the following:
The Validation Tag Helpers (<div asp-validation-summary and <span asp-validation-for) display validation errors. Validation is covered in more detail later in this series.
The Label Tag Helper (<label asp-for="Movie.Title" class="control-label"></label>) generates the label caption and for attribute for the Title property.
The Input Tag Helper (<input asp-for="Movie.Title" class="form-control">) uses the DataAnnotations attributes and produces HTML attributes needed for jQuery Validation on the client-side.
[!div class="step-by-step"] Previous: Adding a model Next: Database
::: moniker-end