Template Authoring

Template Authoring

When to Use

Invoke this skill when:

• User wants to create a custom dotnet new template
• User wants to reverse-engineer a template from an existing project
• User needs to add parameters, post-actions, or constraints to an existing template
• User wants to validate or test a template before publishing

Creating a Template from an Existing Project

Use template_create_from_existing to analyze a .csproj and generate a complete template:

template_create_from_existing with:
  projectPath: "C:/repos/MyProject/MyProject.csproj"
  templateName: "My Custom Template"
  shortName: "mycustomtemplate"
  outputDir: "C:/repos/MyProject/.template.config"

This generates:

• template.json — complete metadata with parameters extracted from project properties
• Templatized .csproj — namespace tokens, conditional sections
• sourceName set for automatic namespace/filename renaming
• Gaps report showing differences from generic dotnet new templates

Template Directory Structure

MyTemplate/
├── .template.config/
│   ├── template.json          # Template metadata (required)
│   ├── ide.host.json          # VS/Rider IDE integration (optional)
│   ├── dotnetcli.host.json    # CLI parameter mappings (optional)
│   └── ai.host.json           # AI assistant metadata (optional)
├── MyProject.csproj           # Project file (templatized)
├── Program.cs                 # Source files
└── ...

template.json Structure

{
  "$schema": "http://json.schemastore.org/template",
  "author": "Your Name",
  "classifications": ["Web", "API"],
  "identity": "MyOrg.MyTemplate.CSharp",
  "name": "My Custom Template",
  "shortName": "mytemplate",
  "sourceName": "MyTemplate",
  "preferNameDirectory": true,
  "tags": {
    "language": "C#",
    "type": "project"
  },
  "symbols": { },
  "sources": [{ "modifiers": [] }],
  "postActions": []
}

Key Fields

Parameter Types (symbols)

"symbols": {
  "Framework": {
    "type": "parameter",
    "datatype": "choice",
    "defaultValue": "net10.0",
    "choices": [
      { "choice": "net10.0", "description": ".NET 10" },
      { "choice": "net9.0", "description": ".NET 9" }
    ],
    "replaces": "net10.0"
  },
  "EnableAot": {
    "type": "parameter",
    "datatype": "bool",
    "defaultValue": "false",
    "description": "Enable Native AOT publishing"
  },
  "copyrightYear": {
    "type": "generated",
    "generator": "now",
    "parameters": { "format": "yyyy" },
    "replaces": "1975"
  }
}

Supported Data Types

Conditional Content

Use C# preprocessor-style directives for conditional content:

#if (EnableAot)
[JsonSerializable(typeof(WeatherForecast))]
internal partial class AppJsonContext : JsonSerializerContext { }
#endif

In .csproj files, use XML comments:

<!--#if (EnableAot) -->
<PublishAot>true</PublishAot>
<!--#endif -->

Post-Actions

Common post-actions to include:

"postActions": [
  {
    "actionId": "210D431B-A78B-4D2F-B762-4ED3E3EA9025",
    "description": "Restore NuGet packages",
    "manualInstructions": [{ "text": "Run 'dotnet restore'" }],
    "continueOnError": true
  },
  {
    "actionId": "84C0DA21-51C8-4541-9940-6CA19AF04EE6",
    "description": "Open README in editor",
    "args": { "files": "README.md" },
    "manualInstructions": [{ "text": "Open README.md" }]
  }
]

Post-Action GUIDs

Constraints

"constraints": {
  "sdk-version": {
    "type": "sdk-version",
    "args": [ "[9.0,)" ]
  },
  "os": {
    "type": "os",
    "args": "Windows"
  },
  "workload": {
    "type": "workload",
    "args": [ "maui" ]
  }
}

Testing a Template

1. Install locally: dotnet new install ./path/to/template/
2. List to verify: dotnet new list mytemplate
3. Dry run: template_dry_run or dotnet new mytemplate --dry-run
4. Create and build: dotnet new mytemplate -n TestProject && dotnet build TestProject
5. Uninstall: dotnet new uninstall ./path/to/template/

Packaging for NuGet

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <PackageType>Template</PackageType>
    <PackageId>MyOrg.Templates</PackageId>
    <PackageVersion>1.0.0</PackageVersion>
    <IncludeContentInPack>true</IncludeContentInPack>
    <IncludeBuildOutput>false</IncludeBuildOutput>
    <ContentTargetFolders>content</ContentTargetFolders>
  </PropertyGroup>
  <ItemGroup>
    <Content Include="templates\**\*" Exclude="templates\**\bin\**;templates\**\obj\**" />
  </ItemGroup>
</Project>

Cross-Reference

• Finding templates → template-discovery skill
• Creating projects from templates → template-instantiation skill
• MSBuild project file best practices → msbuild-style-guide skill (msbuild-skills plugin)