T4Sample (How to Use T4 in .NET Core + VSCode)
This is a sample to create a table Entity class using T4.
In Japanese, see also .NET Core+VS CodeでもT4 テンプレートエンジンでコード生成したい！
Environments
-
.NET Core 3.0 SDK (Preview 7)
-
Visual Studio Code
- Required: C# Extension
- Recommended: T4 Support to highlight T4 Documents.
What is "T4"?
T4 means "Text Template Transformation Toolkit". It is bundled to Visual Studio since 2008.
It is often used for automatic code generation such as table definition classes.
This sample uses Mono.TextTemplating which is a T4 implemented by Mono Project.
Processes
1. Create Project
> dotnet new console2. Add LangVersion to .csproj
- Set
LangVersionto 8.0.
<PropertyGroup>
+ <LangVersion>8.0</LangVersion>
<OutputType>Exe</OutputType>
<TargetFramework>netcoreapp3.0</TargetFramework>
</PropertyGroup>3. Create Table and Column Entities
4. Install Mono.TextTemplating from NuGet
The program code generated by T4 file depends on this package.
> dotnet add package Mono.TextTemplating --version 2.0.55. Install T4 Cli Tool
Add DotNetCliToolReference in csproj to use dotnet-t4-project-tool.
<ItemGroup>
+ <DotNetCliToolReference Include="dotnet-t4-project-tool" Version="2.0.5" />
<PackageReference Include="Mono.TextTemplating" Version="2.0.5" />
</ItemGroup>6. Add Task to Prebuild and Cleanup
Define Target Files
Define TextTemplate and Genarated using Glob.
<ItemGroup>
<DotNetCliToolReference Include="dotnet-t4-project-tool" Version="2.0.5" />
<PackageReference Include="Mono.TextTemplating" Version="2.0.5" />
+ <TextTemplate Include="**\*.tt" />
+ <Generated Include="**\*.Generated.cs" />
</ItemGroup>Define Prebuild Task
Define Task to run dotnet t4.
%(TextTemplate.Identity)- T4 File Paths such as foo/Template.tt.
$(RootNameSpace)- Default Namespace. If you changed the T4 class's namespace, set it exactly.
%(TextTemplate.Filename)- T4 File Name.
</ItemGroup>
+ <Target Name="TextTemplateTransform" BeforeTargets="BeforeBuild">
+ <Exec WorkingDirectory="$(ProjectDir)" Command="dotnet t4 %(TextTemplate.Identity) -c $(RootNameSpace).%(TextTemplate.Filename) -o %(TextTemplate.Filename).Generated.cs" />
+ </Target>Define Cleanup Task
Define Task to delete *.Generated.cs.
</Target>
+ <Target Name="TextTemplateClean" AfterTargets="Clean">
+ <Delete Files="@(Generated)" />
+ </Target>7. Create T4 Interface and define implements
TransFormText(), Called by Program to use T4 Classes are defined in *.Generated.cs.
But *.Generated.cs is generated just before the build.
So calling TransFormText() will cause a compile error because there is no definition at before build time.
This sample avoids this by using the "default implementation of interfaces".
using System;
namespace T4Sample
{
public interface ITextTemplate
{
string TransformText() => throw new NotImplementedException();
}
}8. Create T4 Template File & Class
Note that T4 class should be defined with partial class.
9. Call T4 Class in Program.cs
Note that variable type should be an interface. Don't use var or TableEntityTemplate.
Build & Run
Build
> dotnet buildTableEntityTemplate.Generated.cs is generated and the program is built including it.
Run
dotnet run does not cause Beforebuild-Event, you should execute dotnet build first.
> dotnet runResult
using System;
using System.Collections.Generic;
namespace MyNameSpace
{
/// <summery>
/// Stores employee information.
/// </summery>
public class StaffMaster
{
public int StaffId { get; }
public string StaffName { get; set; }
/// <summery>
/// Home Address.
/// </summery>
public string Address { get; set; }
public DateTime CreatedDate { get; set; }
public StaffMaster(
int staffId
)
{
StaffId = staffId;
}
public StaffMaster(
int staffId,
string staffName,
string address,
DateTime createdDate
)
{
StaffId = staffId;
StaffName = staffName;
Address = address;
CreatedDate = createdDate;
}
}
}