RazorBlade

Compile Razor templates at build-time without a dependency on ASP.NET.

RazorBlade is meant to be lightweight and self-contained: cshtml files are compiled into C# classes at build-time with a Roslyn source generator. No reference to ASP.NET is required.

A simple base class library is provided by default, but it can also be embedded into the target project, or even replaced by your own implementation.

Usage

This package will generate a template class for every .cshtml file in your project.

The generated classes will inherit from RazorBlade.HtmlTemplate by default, though it is advised to specify the base class explicitly to get the best IDE experience:

@inherits RazorBlade.HtmlTemplate

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A version with a model is also available for convenience. The following will add a Model property and a constructor with a ModelType parameter:

@inherits RazorBlade.HtmlTemplate<MyApplication.ModelType>

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Please note that this will cause a constructor with a ModelType parameter to be added to the generated class, which may cause false errors to be shown in some IDEs.

Further documentation is provided below.

Example

The following template, in the ExampleTemplate.cshtml file:

@inherits RazorBlade.HtmlTemplate

Hello, <i>@Name</i>!

@functions
{
    public string? Name { get; init; }
}

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Will generate the following class in your project:

internal partial class ExampleTemplate : RazorBlade.HtmlTemplate
{
    // ...
    public string? Name { get; init; }
    // ...
}

That you can use like the following:

var template = new ExampleTemplate
{
    Name = "World"
};

var result = template.Render();

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With a model

A similar template with a model would be:

@using MyApplication
@inherits RazorBlade.HtmlTemplate<GreetingModel>

Hello, <i>@Model.Name</i>!

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Instantiating the generated class requires a model argument:

var model = new GreetingModel { Name = "World" };
var template = new TemplateWithModel(model);
var result = template.Render();

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Since this generates a constructor with a GreetingModel parameter in the TemplateWithModel class, it may cause false errors to be shown in some IDEs, as they don't recognize this constructor signature.

With a manual model property

Another way of implementing a template with a model is to add a Model property in the template and mark it as required. This will work around false errors which can be shown in some IDEs.

@using MyApplication
@inherits RazorBlade.HtmlTemplate

Hello, <i>@Model.Name</i>!

@functions
{
    public required GreetingModel Model { get; init; }
}

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Instantiating the generated class is done similarly to the previous example:

var model = new GreetingModel { Name = "World" };
var template = new TemplateWithManualModel { Model = model };
var result = template.Render();

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Documentation

Base template classes

For HTML templates, specify one of the following base classes with an @inherits directive:

• RazorBlade.HtmlTemplate
• RazorBlade.HtmlTemplate<TModel>
• RazorBlade.HtmlLayout (for layouts only)

If you'd like to write a plain text template (which never escapes HTML), the following classes are available:

• RazorBlade.PlainTextTemplate
• RazorBlade.PlainTextTemplate<TModel>

They all derive from RazorBlade.RazorTemplate, which provides the base functionality.

You can also write your own base classes. Marking a constructor with [TemplateConstructor] will forward it to the generated template class.

Writing templates

HTML escaping can be avoided by using the @Html.Raw(value) method, just like in ASP.NET. The IEncodedContent interface represents content which does not need to be escaped. The HtmlString class is a simple implementation of this interface.

Templates can be included in other templates by evaluating them, since they implement IEncodedContent. For instance, a Footer template can be included by writing @(new Footer()). Remember to always create a new instance of the template to include, even if it doesn't contain custom code, as templates are stateful and not thread-safe.

The namespace of the generated class can be customized with the @namespace directive. The default value is deduced from the file location.

Layouts

Layout templates may be written by inheriting from the RazorBlade.HtmlLayout class, which provides the relevant methods such as RenderBody and RenderSection. It inherits from RazorBlade.HtmlTemplate.

The layout to use can be specified through the Layout property of RazorBlade.HtmlTemplate. Given that all Razor templates are stateful and not thread-safe, always create a new instance of the layout page to use:

@{
    Layout = new LayoutToUse();
}

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Layout pages can be nested, and can use sections. Unlike in ASP.NET, RazorBlade does not verify if the body and all sections have been used. Sections may also be executed multiple times.

Executing templates

The RazorTemplate base class provides Render and RenderAsync methods to execute the template.

Templates are stateful and not thread-safe, so it is advised to always create new instances of the templates to render.

Flushing partial output

By default, the output of a template is buffered while it is executing, then copied to the provided writer when finished. This is necessary for features such as layouts to be supported, but may not always be desired.

The RazorTemplate class provides a FlushAsync method which will copy the buffered output to the provided TextWriter and then flush the writer:

<div>Lightweight content goes here.</div>
@await FlushAsync()
<div>Slower to render content goes here.</div>

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Important

Flushing is not compatible with layout usage.

MSBuild

The source generator will process RazorBlade MSBuild items which have the .cshtml file extension.

By default, all .cshtml files are included, unless one of the EnableDefaultRazorBladeItems or EnableDefaultItems properties are set to false. You can also manually customize this set.

Removing the dependency on RazorBlade

RazorBlade makes it possible to remove the dependency on its runtime assembly. This could be useful for library projects which should be self-contained, with no dependencies on external packages.

This mode is enabled by default when the PackageReference of RazorBlade has the PrivateAssets="all" attribute. In order to avoid compilation warnings, the assembly reference also needs to be explicitly excluded with ExcludeAssets="compile;runtime".

<PackageReference Include="RazorBlade" Version="..." ExcludeAssets="compile;runtime" PrivateAssets="all" />

A source generator will then embed an internal version of the RazorBlade library in the target project. This behavior can also be controlled by setting the RazorBladeEmbeddedLibrary MSBuild property to true or false.