Generic data interface

I currently have the following working code. I am looking for some suggestion with best practices and perhaps a better way to accomplish my goal.

Goal: - in short - Have a generic data interface as a single data access point to different data sources.

Concern: My current code is working fine but I have to call GetRepository() in each method inside my test class to access the desire instance of the data source repository.

Code Snippet:

public class GenericRepository : IGenericRepository
{
   public T GetRepository<T>() 
    {
        string typeName = typeof(T).ToString();
        if (string.IsNullOrEmpty(typeName))
            return default(T);

        Type repoType = Type.GetType(typeName);
        object repoInstance = Activator.CreateInstance(repoType);
        return (T)(object)repoInstance;
    }
    // more code... 
}

Usage:

public class MyTestClass
{
    IGenericRepository repo = new GenericRepository();

    private void DoThis()
    {
       IFileRepository repoA = repo.GetRepository<FileRepository>();
       // now I can call repository A interface methods like this repoA.SomeMethod()
    }

    private void DoThat()
    {
        ISQLRepository repoB = repo.GetRepository<SQLRepository>();
        // now do something with repository B interface methods like this repoB.SomeMethod()
    }
}

I thought of an alternative way to do this but it has its own drawbacks as well.

1. Implement the interface methods in both IGenericeRepository and as well as the interface I inherited.

2. Implement the methods for inherited interface inside IGenericRepository and put it in each different region and end up with a massive page of code

Thoughts? Comments? Suggestion? -- I personally think the first option is a better choice but wonder if there are better ideas or maybe there is something wrong with my implementation.

Alternative Code

public class GenericRepository : IGenericRepository, IFileRepository, ISQLRepository
{
   public FileRepository fileRepo { get; set; }
   public SQLRepository sqlRepo { get; set; }

   public GenericRepository()
   {
       fileRepo = new FileRepository();
       sqlRepo = new SQLRepository();
   }
    // more code... 
}

Alternative Usage

public class MyTestClass
{
    IGenericRepository repo = new GenericRepository();

    private void DoThis()
    {
         // now I can access file repository like this: repo.fileRepo.SomeMethod();
         // now I can access sql repository methods like this: repo.sqlRepo.SomeMethod();
    }

    private void DoThat()
    {
         // now I can access file repository like this: repo.fileRepo.SomeMethod();
         // now I can access sql repository methods like this: repo.sqlRepo.SomeMethod();
    }
}

====== updated:

To provide more context. Below is the solution structure

-- Solution

---- Repository Project (GenericRepository, FileRepository, SQLRepository)

---- IRepository Project (IGenericRepository, IFileRepository, ISQLRepository)

---- MyTestProject Project (MyTestClass)