Refactor code into using statement

Question

I have a dal layer with lots of methods, all of them call stored procedures, some return lists (so with a use of SqlDataReader), others only a specific value.

I have a helper method that creates the SqlCommand:

    protected SqlCommand CreateSprocCommand(string name, bool includeReturn, SqlDbType returnType)
    {
        SqlConnection con = new SqlConnection(this.ConnectionString);
        SqlCommand com = new SqlCommand(name, con);
        com.CommandType = System.Data.CommandType.StoredProcedure;

        if (includeReturn)
            com.Parameters.Add("ReturnValue", returnType).Direction = ParameterDirection.ReturnValue;

        return com;
    }

Now my average (overly simplified) method body look like:

SqlCommand cmd = CreateSprocCommand("SomeSprocName"); //an override of the above mentioned method
try {
   cmd.Connection.Open();
   using (var reader = cmd.ExecuteReader()) {
       //some code looping over the recors
   }
   //some more code to return whatever needs to be returned
}
finally {
   cmd.Connection.Dispose();
}

Is there a way to refactor this, so that I won't lose my helper function (it does quite a bit of otherwise repetitive work), and yet be able to use using?

Answer 1

One way is to change it from returning a command to taking a delegate which uses the command:

protected void ExecuteSproc(string name,
                            SqlDbType? returnType,
                            Action<SqlCommand> action)
{
    using (SqlConnection con = new SqlConnection(this.ConnectionString))
    using (SqlCommand com = new SqlCommand(name, con))
    {
        con.Open();
        com.CommandType = System.Data.CommandType.StoredProcedure;

        if (returnType != null)
        {
            com.Parameters.Add("ReturnValue", returnType.Value).Direction = 
                ParameterDirection.ReturnValue;
        }
        action(com);
    }
}

(Note that I've also removed the includeReturn parameter and made returnType nullable instead. Just pass null for "no return value".)

You'd use this with a lambda expression (or anonymous method):

ExecuteSproc("SomeName", SqlDbType.DateTime, cmd =>
{
    // Do what you want with the command (cmd) here
});

That way the disposal is in the same place as the creation, and the caller just doesn't need to worry about it. I'm becoming quite a fan of this pattern - it's a lot cleaner now that we've got lambda expressions.