如何使用.cs.t4模板生成代码？接手项目遇模板运行困惑

Hey there! Let me break down how to run this parameterized T4 template you found. Unlike the auto-generating T4 templates you've seen in tutorials, this one is designed to take custom parameters (like ControllerName, Namespace) before it can generate a valid .cs file—here's exactly what you can do:

Why It Doesn't Auto-Generate #

First, notice the <#@ parameter #> directives at the top of your template. These mean the template requires external input values to work—without them, it can't produce a complete, valid controller class. That's why it doesn't auto-generate like simpler T4 templates.

Method 1: Use a "Driver" T4 Template (Easiest in Visual Studio) #

Create a new T4 template file (e.g., GenerateController.tt) in the same directory as Controller.cs.t4, then add this code to it:

<#@ template language="C#" #>
<#@ include file="Controller.cs.t4" #>
<#
    // Fill in your desired parameter values here
    ControllerName = "HomeController";
    ControllerRootName = "Home";
    Namespace = "YourProjectNamespace.Controllers";
    AreaName = ""; // Leave empty if no area, or set to something like "Admin"
    
    // Trigger the template generation
    this.Generate();
#>

Once you save this driver template, Visual Studio will automatically process it and generate a .cs file (e.g., GenerateController.cs) with your fully populated controller class. You can tweak the parameter values anytime and re-save to regenerate.

Method 2: Call the Template via C# Code (For Custom Automation) #

If you want more control (like integrating this into a build script or tool), you can use the Templating Engine API to run the template programmatically. Here's a simplified example:

using Microsoft.VisualStudio.TextTemplating;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        // Initialize the T4 engine
        var engine = new Engine();
        string templatePath = @"Path\To\Your\Controller.cs.t4";
        string templateContent = File.ReadAllText(templatePath);

        // Set up your parameter values
        var session = new TextTemplatingSession();
        session["ControllerName"] = "ProductController";
        session["ControllerRootName"] = "Product";
        session["Namespace"] = "YourProject.Controllers";
        session["AreaName"] = "Catalog";

        // Create a simple host to handle parameter resolution
        var host = new CustomTemplateHost { Session = session };

        // Process the template and get the output
        string generatedCode = engine.ProcessTemplate(templateContent, host);

        // Save the generated controller to a file
        File.WriteAllText(@"Path\To\Output\ProductController.cs", generatedCode);
    }
}

// Minimal implementation of the ITextTemplatingEngineHost interface
public class CustomTemplateHost : ITextTemplatingEngineHost
{
    public TextTemplatingSession Session { get; set; }

    public object GetHostOption(string optionName) => null;
    public bool LoadIncludeText(string requestFileName, out string content, out string location)
    {
        content = string.Empty;
        location = string.Empty;
        return false;
    }
    public void LogErrors(CompilerErrorCollection errors) { }
    public AppDomain ProvideTemplatingAppDomain(string content) => AppDomain.CurrentDomain;
    public string ResolveAssemblyReference(string assemblyReference) => assemblyReference;
    public Type ResolveDirectiveProcessor(string processorName) => null;
    public string ResolvePath(string path) => path;
    public string ResolveParameterValue(string directiveId, string processorName, string parameterName)
    {
        return Session[parameterName]?.ToString();
    }
    public void SetFileExtension(string extension) { }
    public void SetOutputEncoding(System.Text.Encoding encoding, bool fromOutputDirective) { }
}

Notes #

• Make sure you have the Text Template Transformation component installed in Visual Studio (you can add it via the Visual Studio Installer if missing).
• When using the driver template, ensure the include path points correctly to Controller.cs.t4 if they're in different directories.
• Adjust the parameter values (ControllerName, Namespace, etc.) to match your project's structure.

内容的提问来源于stack exchange，提问作者Josy Sclei