public abstract class Base : IDisposable
{
protected SqlCommand command = null;
        protected SqlDataReader reader = null;
        private string connectionString = string.Empty;

public Base(string connectionString)
        {
            this.connectionString = connectionString;
        }

protected bool Init()
        {
            if (command == null) command = new SqlCommand();
            if (command.Connection == null) command.Connection = new SqlConnection(connectionString);
            if (command.Connection.State != ConnectionState.Open)
            {
                try
                {
                    command.Connection.Open();
                }
                catch
                {
                    command.Dispose();
                    command = null;
                    return false;
                }
            }
            command.CommandType = CommandType.Text;
            return true;
        }

public void Dispose(bool disposing)
        {
            if (!disposed)
            {
                if (disposing)
                {
                    try
                    {
                        command.Connection.Close();
                        command.Connection.Dispose();
                        command.Dispose();
                    }
                    catch { }
                    finally
                    {
                        CloseReader();
                        disposed = true;
                    }
                }
            }
            disposed = true;
        }

protected void AddParameter(DbParameter parameter)
        {
// прописать логику для добавления параметров
}
//... и другие функции 
}