dotnet-t4 3.0.0-preview-0045-g9b6fc72764

dotnet-t4

dotnet-t4 is a command-line tool for processing T4 templates, a general-purpose way to generate text or code files using C#.

It's part of Mono.TextTemplating, a modern open-source reimplementation of the Visual Studio T4 text templating engine.

Example

A T4 template file contains text interleaved with C# or VB.NET code blocks, which is used to generate a template class, then optionally compiled and executed to generate textual output.

Here is an example T4 template, powers.tt. It generates a Markdown table of squares and cubes for numbers up to the value specified by the parameter Max.

<#@ output extension=".md" #>
<#@ parameter name="Max" type="int" #>
<#@ import namespace="System.Linq" #>
# Table of Powers
Number | Square | Cube
--- | ---
<# foreach(int i in Enumerable.Range(2,Max)) {#>
<#= i #> | <#= i*i #> | <#= i*i*i #>
<#}#>

It can be executed by running t4 powers.tt -p:Max=6, which produces the following powers.md markdown file:

# Table of Powers
Number | Square | Cube
--- | ---
2 | 4 | 8
3 | 9 | 27
4 | 16 | 64
5 | 25 | 125
6 | 36 | 216

Alternatively, invoking t4 powers.tt -c MyApp.Powers will produce a powers.cs file containing the runtime template class, which you can compile into your app and execute at runtime with new parameter values:

var template = new MyApp.Powers {
    Session = new Dictionary<string, object> {
        { "Max", 10 }
    }
};
template.Initialize();
string powersTableMarkdown = template.TransformText();

To learn more about the T4 language, see the Visual Studio T4 documentation.

Usage

t4 is a CLI tool and may be invoked as follows:

t4 [options] [template-file]

The template-file argument is required unless the template text is piped in via stdin.

Differences from VS T4

The Mono.TextTemplating engine contains many improvements over the original Visual Studio T4 implementation, including:

• It supports the latest .NET APIs and C# language version
• The engine and the code it generates are compatible with .NET Core and .NET 5+
• Parameter directives may use primitive types: <#@ parameter name="Foo" type="int" #>
• Parameter values passed on the CLI will be automatically converted to the type specified in the parameter directive.
• The CLI can read templates from standard input and output to standard output

Several of these features are demonstrated in the following bash one-liner:

$  echo '<#@ parameter name="Date" type="System.DateTime" #>That was a <#=$"{Date:dddd}"#>' | t4 -o - -p:Date="2016/3/8"
That was a Tuesday