BaseModel.cs

public class BaseModel
{
    public BaseModel()
    {
        IsActive = true;
    }

    public int Id { get; set; }

    public bool IsActive { get; set; }

    public DateTime CreatedDate { get; set; }

    public string CreatedUser { get; set; }

    public DateTime UpdatedDate { get; set; }

    public string UpdatedUser { get; set; }
}

IRepository.cs

public interface IRepository<T> where T : BaseModel, new()
{
    void Add(T entity);

    void Delete(T entity);

    void Delete(int id);

    T GetById(int id);

    IQueryable<T> GetAllActive();

    IQueryable<T> GetAll();

    void SaveChanges();
}

IRepositoryGenerator.tt

<#@ include file="IRepositoryTemplate.tt" #>
<#+
// <copyright file="IRepositoryGenerator.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

public class IRepositoryGenerator : Generator
{
	public IRepositoryTemplate Template = new IRepositoryTemplate();

	protected override void RunCore()
	{
		var classes = new string[]{"User", "Product"};

		foreach(var className in classes){
			Template.ClassName = className;
			Template.RenderToFile("I" + className + "Repository.generated.cs");
		}
	}
}
#>

IRepositoryScript.tt

<#@ template language="C#" debug="True" #>
<#@ output extension="cs" #>
<#@ include file="T4Toolbox.tt" #>
<#@ include file="IRepositoryGenerator.tt" #>
<#
// <copyright file="IRepositoryScript.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

	IRepositoryGenerator generator = new IRepositoryGenerator();
	generator.Run();
#>

IRepositoryTemplate.tt

<#+
// <copyright file="IRepositoryTemplate.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

public class IRepositoryTemplate : CSharpTemplate
{
	public string ClassName;

	public override string TransformText()
	{
		base.TransformText();
#>
using T4Repositories.Models;

namespace <#= DefaultNamespace #>
{
	public partial interface I<#= Identifier(ClassName) #>Repository : IRepository<<#= Identifier(ClassName) #>>
	{
		
	}
}
<#+
        return this.GenerationEnvironment.ToString();
	}
}
#>

IUserRepository.cs

// <autogenerated>
//   This file was generated by T4 code generator IRepositoryScript.tt.
//   Any changes made to this file manually will be lost next time the file is regenerated.
// </autogenerated>

using T4Repositories.Models;

namespace T4Repositories.Logic.Repositories
{
	public partial interface IUserRepository : IRepository<User>
	{
		
	}
}

Repository.cs

public abstract class Repository<T> : IRepository<T> where T : BaseModel, new()
{
    public Repository(Lazy<DataContext> dataContext)
    {
        if (dataContext == null)
        {
            throw new ArgumentNullException("dataContext");
        }
        _dataContext = dataContext;
    }

    private Lazy<DataContext> _dataContext;

    protected DataContext DataContext
    {
        get
        {
            return _dataContext.Value;
        }
    }

    public void Add(T entity)
    {
        DataContext.Set<T>().Add(entity);
    }

    public void Delete(T entity)
    {
        DataContext.Set<T>().Remove(entity);
    }

    public void Delete(int id)
    {
        T entity = new T()
        {
            Id = id
        };

        DataContext.Entry(entity).State = EntityState.Deleted;
    }

    public T GetById(int id)
    {
        return DataContext.Set<T>().FirstOrDefault(e => e.Id == id);
    }

    public IQueryable<T> GetAllActive()
    {
        return DataContext.Set<T>().Where(e => e.IsActive);
    }

    public IQueryable<T> GetAll()
    {
        return DataContext.Set<T>();
    }

    public void SaveChanges()
    {
        DataContext.SaveChanges();
    }
}

RepositoryGenerator.tt

<#@  include file="RepositoryTemplate.tt" #>
<#@ assembly name="System" #>
<#+
// <copyright file="RepositoryGenerator.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

public class RepositoryGenerator : Generator
{
	public RepositoryTemplate Template = new RepositoryTemplate();

	protected override void RunCore()
	{
		var classes = new string[]{"User", "Product"};

		foreach(var item in classes){
			Template.ClassName = item;
			Template.RenderToFile(item + "Repository.generated.cs");
        }
	}
}
#>

RepositoryScript.tt

<#@ template language="C#" debug="True" #>
<#@ output extension="cs" #>
<#@ include file="T4Toolbox.tt" #>
<#@ include file="RepositoryGenerator.tt" #>
<#
// <copyright file="RepositoryScript.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

	RepositoryGenerator generator = new RepositoryGenerator();
	generator.Run();
#>

RepositoryTemplate.tt

<#+
// <copyright file="RepositoryTemplate.tt" company="">
//  Copyright © . All Rights Reserved.
// </copyright>

public class RepositoryTemplate : CSharpTemplate
{
	public string ClassName;

	public override string TransformText()
	{
		base.TransformText();
#>
using T4Repositories.Models;
using T4Repositories.Logic.Repositories;
using System;

namespace <#= DefaultNamespace #>
{
	public partial class <#= Identifier(ClassName) #>Repository : Repository<<#= Identifier(ClassName) #>>, I<#= Identifier(ClassName) #>Repository
	{
		public <#= Identifier(ClassName) #>Repository(Lazy<DataContext> db)
			: base(db)
			{

			}
	}
}
<#+
        return this.GenerationEnvironment.ToString();
	}
}
#>