Minimal Db Helper

DbHelper.cs

namespace DbHelper
{
    public class OleDbHelper : DbHelper<OleDbConnection>
    {
        public static DbParameter CreateParameter(string name, object value)
        {
            return new OleDbParameter(name, value);
        }
    }

    public class SqlDbHelper : DbHelper<SqlConnection>
    {
        public static DbParameter CreateParameter(string name, object value)
        {
            return new SqlParameter(name, value);
        }
    }

    public class DbHelper<TC> where TC : DbConnection
    {
        public static DbDataReader ExecuteReader(string connectionString, string sql, params DbParameter[] pars)
        {
            return ExecuteCommand<TC, DbDataReader>(
                connectionString, sql,
                (Cx, Cd) =>
                {
                    Cx.Open();
                    return Cd.ExecuteReader(CommandBehavior.CloseConnection);
                },
                pars);
        }

        public static int Execute(string connectionString, string sql, params DbParameter[] pars)
        {
            return ExecuteCommand<TC, int>(
                connectionString, sql,
                (Cx, Cd) =>
                {
                    Cx.Open();
                    try
                    {
                        return Cd.ExecuteNonQuery();
                    }
                    finally
                    {
                        Cx.Close();
                    }
                },
                pars);
        }

        public static T ExecuteScalar<T>(string connectionString, string sql, params DbParameter[] pars)
        {
            return ExecuteCommand<TC, T>(
                connectionString, sql,
                (Cx, Cd) =>
                {
                    Cx.Open();
                    try
                    {
                        var Obj = Cd.ExecuteScalar();
                        if (Obj == DBNull.Value)
                            return default(T);
                        else
                        {
                            return (T)Obj;
                        }
                    }
                    finally
                    {
                        Cx.Close();
                    }
                },
                pars);
        }

        static T3 ExecuteCommand<T, T3>(string connectionString, string sql, Func<T, DbCommand, T3> action, params DbParameter[] pars) where T : DbConnection
        {
            T3 ReturnValue;

            var Cx = Activator.CreateInstance<T>();
            Cx.ConnectionString = connectionString;

            using (var Cd = Cx.CreateCommand())
            {
                Cd.CommandText = sql;
                if (sql.StartsWith("sp", StringComparison.InvariantCultureIgnoreCase))
                    Cd.CommandType = CommandType.StoredProcedure;

                if (pars != null && pars.Length > 0)
                    Cd.Parameters.AddRange(pars);

                ReturnValue = action(Cx, Cd);
            }

            return ReturnValue;
        }
    }
}