Proposal: Razor-like templating syntax inside raw string literals #9586

wiktor-golonka · 2025-08-05T21:29:12Z

wiktor-golonka
Aug 5, 2025

Summary

Introduce a new string literal form that supports embedded C# expressions and simple control flow (e.g., @variable, @foreach, @if) in a Razor-like syntax, primarily for use in source generation and templating scenarios.

Motivation

Currently, raw string literals and interpolated strings are awkward to use for generating structured content like HTML, code, or configuration files when logic is involved.

No support for control flow like foreach or if.
Escaping braces ({{ }}) in nested templating scenarios is painful.

This proposal aims to bring templating support, using a Razor-like syntax, directly into the C# language for improved ergonomics in scenarios like source generators, code emitters, etc.

Examples

HTML Email Template

Current (clunky):

var html = $$"""
<html>
<body>
    <p>Hello, {{user.Name}}</p>
</body>
</html>
""";

Proposed (templated block):

var html = razor"""
<html>
<body>
    <p>Hello, @user.Name</p>

    @if (user.IsAdmin)
    {
        <p>You have admin rights.</p>
    }
</body>
</html>
""";

C# Source Generator Emitting Code

Current (clunky):

var sb = new StringBuilder();

sb.AppendLine($"namespace {ns}");
sb.AppendLine("{");
sb.AppendLine($"    public class {className}");
sb.AppendLine("    {");

foreach (var prop in properties)
{
    sb.AppendLine($"        public {prop.Type} {prop.Name} {{ get; set; }}");
}

sb.AppendLine("    }");
sb.AppendLine("}");

var code = sb.ToString();

Proposed (templated block):

var code = razor"""
namespace @ns
{
    public class @className
    {
        @foreach (var prop in properties)
        {
            public @prop.Type @prop.Name { get; set; }
        }
    }
}
""";

Benefits

Safer and cleaner than string interpolation for large blocks
Familiar syntax for .NET developers
Better readability and maintainability
Removes the need for external templating engines
Ideal for source generators, code emitters, and email templates

I’m curious if this is something that could be supported by the language.

ufcpp · 2025-08-06T00:55:56Z

ufcpp
Aug 6, 2025

That should be implemented using Source Generator. I have implemented something similar to that with scriban: ScribanSourceGenerator.

4 replies

wiktor-golonka Aug 6, 2025
Author

I'm not sure if it can be implemented using Source Generator if I want to utilise it in Source Generators. Even more, I don't understand why you are saying that it should be implemented with SG.

ufcpp Aug 6, 2025

As many discussions have concluded many times, we should not have another language within a language.

wiktor-golonka Aug 8, 2025
Author

@ufcpp: I see this more as syntax sugar added to C#’s existing string features than as another language within a language.
We already have string interpolation, this would be the next step, enabling more complex scenarios while still lowering to familiar string operations.

From my experience with source generators, this would be a huge improvement. Writing complex output today means juggling StringBuilders, escaping, and indentation, which is hard to read and maintain. A Razor-style literal would make that far more readable while staying entirely within C#.

HaloFour Aug 8, 2025

It is another language within a language, though, with it's own set of control statements that work differently than they would in the normal C# language. It's about turning string interpolation into an entire templating engine, which would be no small feat.

GabeSchaffer · 2025-08-06T05:46:45Z

GabeSchaffer
Aug 6, 2025

Is your proposal any different from #7532?

Your request is also similar to #8756.

1 reply

wiktor-golonka Aug 6, 2025
Author

Hi @GabeSchaffer

It's quite similar to #7532, but I don't think it's similar to #8756.

The main difference from 7532 is that it's not about making it easier specifically for ASP.NET Core, but in general to make working with larger string templates easier.

Since now we have the source generators something like this would drastically improve the readability of the code.

siegfriedpammer · 2025-08-11T03:58:51Z

siegfriedpammer
Aug 11, 2025

What's so clunky about the first example?
Also, I believe you are comparing apples to oranges in your second example...

I have written a source generator myself and while it may be confusing at first that one has to produce strings instead of Roslyn AST. It's certainly the most flexible approach.

What's so bad about multi-line/verbatim interpolated strings? If you need conditions, you can use conditional expressions inside the interpolations. If it's more complicated logic, you can use a local function.

I think c# has enough flavors of string literals already:

verbatim strings
interpolated strings
verbatim interpolated strings
raw strings
raw interpolated strings

Why add another one? Like I said, if you need conditions, you can use conditional expressions inside the interpolations. If it's more complicated logic, you can use a local function.

0 replies

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Proposal: Razor-like templating syntax inside raw string literals #9586

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Proposal: Razor-like templating syntax inside raw string literals #9586

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wiktor-golonka Aug 5, 2025

Summary

Motivation

Examples

HTML Email Template

C# Source Generator Emitting Code

Benefits

Replies: 3 comments · 5 replies

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ufcpp Aug 6, 2025

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wiktor-golonka Aug 6, 2025 Author

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ufcpp Aug 6, 2025

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wiktor-golonka Aug 8, 2025 Author

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HaloFour Aug 8, 2025

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GabeSchaffer Aug 6, 2025

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wiktor-golonka Aug 6, 2025 Author

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siegfriedpammer Aug 11, 2025

wiktor-golonka
Aug 5, 2025

Replies: 3 comments 5 replies

ufcpp
Aug 6, 2025

wiktor-golonka Aug 6, 2025
Author

wiktor-golonka Aug 8, 2025
Author

GabeSchaffer
Aug 6, 2025

wiktor-golonka Aug 6, 2025
Author

siegfriedpammer
Aug 11, 2025