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Statically-rendered layout components (#35344)
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aspnetcore/blazor/components/built-in-components.md

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@@ -37,7 +37,7 @@ The following built-in Razor components are provided by the Blazor framework. Fo
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavigationLock`](xref:blazor/fundamentals/routing#handleprevent-location-changes)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavigationLock`](xref:blazor/fundamentals/routing#handleprevent-location-changes)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavigationLock`](xref:blazor/fundamentals/routing#handleprevent-location-changes)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`OwningComponentBase`](xref:fundamentals/dependency-injection#utility-base-component-classes-to-manage-a-di-scope)
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`OwningComponentBase`](xref:fundamentals/dependency-injection#utility-base-component-classes-to-manage-a-di-scope)
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* [`InputSelect`](xref:blazor/forms/input-components)
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* [`InputText`](xref:blazor/forms/input-components)
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* [`InputTextArea`](xref:blazor/forms/input-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#layout-components)
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* [`LayoutComponentBase`](xref:blazor/components/layouts#create-a-layout-component)
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* [`LayoutView`](xref:blazor/components/layouts#apply-a-layout-to-arbitrary-content-layoutview-component)
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* [`NavLink`](xref:blazor/fundamentals/routing#navlink-component)
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* [`OwningComponentBase`](xref:fundamentals/dependency-injection#utility-base-component-classes-to-manage-a-di-scope)

aspnetcore/blazor/components/layouts.md

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A Blazor layout is a Razor component that shares markup with components that reference it. Layouts can use [data binding](xref:blazor/components/data-binding), [dependency injection](xref:blazor/fundamentals/dependency-injection), and other features of components.
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## Layout components
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### Create a layout component
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## Create a layout component
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To create a layout component:
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:::moniker-end
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### `MainLayout` component
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## `MainLayout` component
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In an app created from a [Blazor project template](xref:blazor/project-structure), the `MainLayout` component is the app's [default layout](#apply-a-default-layout-to-an-app). Blazor's layout adopts the [:::no-loc text="Flexbox"::: layout model](https://developer.mozilla.org/docs/Glossary/Flexbox) ([W3C specification](https://www.w3.org/TR/css-flexbox-1/)).
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:::moniker-end
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:::moniker range=">= aspnetcore-8.0"
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<!-- UPDATE 11.0 Is https://github.com/dotnet/aspnetcore/issues/52768 addressed
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to resolve the following limitation? -->
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## Statically-rendered layout components
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When a Blazor Web App adopts per-page/component rendering (the `Routes` component doesn't specify an interactive render mode), layout components are rendered statically on the server. Applying an interactive render mode directly to a layout isn't supported because Blazor doesn't support serializing a <xref:Microsoft.AspNetCore.Components.RenderFragment> (`@Body` in this case) as a root component parameter. For example, placing `@rendermode InteractiveServer` at the top of the `MainLayout` component results in the following runtime exception:
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> :::no-loc text="System.InvalidOperationException: Cannot pass the parameter 'Body' to component 'MainLayout' with rendermode 'InteractiveServerRenderMode'. This is because the parameter is of the delegate type 'Microsoft.AspNetCore.Components.RenderFragment', which is arbitrary code and cannot be serialized.":::
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This applies to any layout component that inherits from <xref:Microsoft.AspNetCore.Components.LayoutComponentBase> in an app that adopts per-page/component rendering.
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This scenario might be addressed in a future release of Blazor. For more information, see [[Blazor] Support serializing render fragments from SSR (`dotnet/aspnetcore` #52768)](https://github.com/dotnet/aspnetcore/issues/52768). In the meantime, you can adopt the following approach in a Blazor Web App that adopts per-page/component rendering.
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Create a wrapper component that's capable of interactivity. In the following example, a wrapper component contains a [Blazor section](xref:blazor/components/sections) that can receive content from a child component.
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In the `_Imports.razor` file, add an [`@using`](xref:mvc/views/razor#using) directive for sections (<xref:Microsoft.AspNetCore.Components.Sections?displayProperty=fullName>):
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```razor
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@using Microsoft.AspNetCore.Components.Sections
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```
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Create the following interactive wrapper component in the `Pages` folder.
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`Pages/InteractiveWrapper.razor`:
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```razor
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@rendermode InteractiveServer
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<div>
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<SectionOutlet SectionName="top-bar" />
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</div>
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@ChildContent
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@code {
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[Parameter]
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public RenderFragment? ChildContent { get; set; }
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}
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```
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The `Counter` component can use the wrapper component and set interactive section content. In the following example, a counter button is placed in the section.
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`Pages/Counter.razor`:
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```razor
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@page "/counter"
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@rendermode InteractiveServer
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<InteractiveWrapper>
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<SectionContent SectionName="top-bar">
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<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
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</SectionContent>
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<PageTitle>Counter</PageTitle>
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<h1>Counter</h1>
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<p role="status">Current count: @currentCount</p>
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<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
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</InteractiveWrapper>
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@code {
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private int currentCount = 0;
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private void IncrementCount()
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{
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currentCount++;
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}
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}
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```
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Other components around the app can also wrap content in the `InteractiveWrapper` component and set interactive section content.
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:::moniker-end
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## Apply a layout
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### Make the layout namespace available
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<RouteView RouteData="routeData" DefaultLayout="typeof({LAYOUT})" />
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In the preceding example, the `{LAYOUT}` placeholder is the layout (for example, `DoctorWhoLayout` if the layout file name is `DoctorWhoLayout.razor`). You may need to idenfity the layout's namespace depending on the .NET version and type of Blazor app. For more information, see the [Make the layout namespace available](#make-the-layout-namespace-available) section.
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In the preceding example, the `{LAYOUT}` placeholder is the layout (for example, `DoctorWhoLayout` if the layout file name is `DoctorWhoLayout.razor`). You may need to identify the layout's namespace depending on the .NET version and type of Blazor app. For more information, see the [Make the layout namespace available](#make-the-layout-namespace-available) section.
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Specifying the layout as a default layout in the <xref:Microsoft.AspNetCore.Components.Routing.Router> component's <xref:Microsoft.AspNetCore.Components.RouteView> is a useful practice because you can override the layout on a per-component or per-folder basis, as described in the preceding sections of this article. We recommend using the <xref:Microsoft.AspNetCore.Components.Routing.Router> component to set the app's default layout because it's the most general and flexible approach for using layouts.
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aspnetcore/blazor/components/render-modes.md

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> :::no-loc text="System.InvalidOperationException: Cannot pass the parameter 'ChildContent' to component 'SharedMessage' with rendermode 'InteractiveServerRenderMode'. This is because the parameter is of the delegate type 'Microsoft.AspNetCore.Components.RenderFragment', which is arbitrary code and cannot be serialized.":::
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<!-- UPDATE 11.0 Is https://github.com/dotnet/aspnetcore/issues/52768 addressed
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to resolve the following limitation? -->
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The same thing happens if you attempt to adopt interactive rendering in a layout that inherits from <xref:Microsoft.AspNetCore.Components.LayoutComponentBase>, such as the app's `MainLayout` component, in an app that adopts per-page/component rendering. For more information, see <xref:blazor/components/layouts#statically-rendered-layout-components>.
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To circumvent the preceding limitation, wrap the child component in another component that doesn't have the parameter. This is the approach taken in the Blazor Web App project template with the `Routes` component (`Components/Routes.razor`) to wrap the <xref:Microsoft.AspNetCore.Components.Routing.Router> component.
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`WrapperComponent.razor`:

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