How to implement Unit Of Work pattern with Dapper?

This Git project is very helpful. I started from the same and did some changes as per my need.

public sealed class DalSession : IDisposable
{
    public DalSession()
    {
        _connection = new OleDbConnection(DalCommon.ConnectionString);
        _connection.Open();
        _unitOfWork = new UnitOfWork(_connection);
    }

    IDbConnection _connection = null;
    UnitOfWork _unitOfWork = null;

    public UnitOfWork UnitOfWork
    {
        get { return _unitOfWork; }
    }

    public void Dispose()
    {
        _unitOfWork.Dispose();
        _connection.Dispose();
    }
}

public sealed class UnitOfWork : IUnitOfWork
{
    internal UnitOfWork(IDbConnection connection)
    {
        _id = Guid.NewGuid();
        _connection = connection;
    }

    IDbConnection _connection = null;
    IDbTransaction _transaction = null;
    Guid _id = Guid.Empty;

    IDbConnection IUnitOfWork.Connection
    {
        get { return _connection; }
    }
    IDbTransaction IUnitOfWork.Transaction
    {
        get { return _transaction; }
    }
    Guid IUnitOfWork.Id
    {
        get { return _id; }
    }

    public void Begin()
    {
        _transaction = _connection.BeginTransaction();
    }

    public void Commit()
    {
        _transaction.Commit();
        Dispose();
    }

    public void Rollback()
    {
        _transaction.Rollback();
        Dispose();
    }

    public void Dispose()
    {
        if(_transaction != null)
            _transaction.Dispose();
        _transaction = null;
    }
}

interface IUnitOfWork : IDisposable
{
    Guid Id { get; }
    IDbConnection Connection { get; }
    IDbTransaction Transaction { get; }
    void Begin();
    void Commit();
    void Rollback();
}

Now, your repositories should accept this UnitOfWork in some way. I choose Dependency Injection with Constructor.

public sealed class MyRepository
{
    public MyRepository(IUnitOfWork unitOfWork) 
    {
        this.unitOfWork = unitOfWork;
    }

    IUnitOfWork unitOfWork = null;

    //You also need to handle other parameters like 'sql', 'param' ect. This is out of scope of this answer.
    public MyPoco Get()
    {
        return unitOfWork.Connection.Query(sql, param, unitOfWork.Transaction, .......);
    }

    public void Insert(MyPoco poco)
    {
        return unitOfWork.Connection.Execute(sql, param, unitOfWork.Transaction, .........);
    }
}

And then you call it like this:

With transaction:

using(DalSession dalSession = new DalSession())
{
    UnitOfWork unitOfWork = dalSession.UnitOfWork;
    unitOfWork.Begin();
    try
    {
        //Your database code here
        MyRepository myRepository = new MyRepository(unitOfWork);
        myRepository.Insert(myPoco);
        //You may create other repositories in similar way in same scope of UoW.

        unitOfWork.Commit();
    }
    catch
    {
        unitOfWork.Rollback();
        throw;
    }
}

Without Transaction:

using(DalSession dalSession = new DalSession())
{
    //Your database code here
    MyRepository myRepository = new MyRepository(dalSession.UnitOfWork);//UoW have no effect here as Begin() is not called.
    myRepository.Insert(myPoco);
}

Please note that, UnitOfWork is more than DBTransaction.

More details about Repository in above code could be found here.

I have already post this code here. But this question looks more relevant to me for this code; so I am posting again instead of just link to original answer.