DbCommand Extensions

public static DbCommand AddInParameter(this DbCommand cmd, string parameterName, object value)
        {
            DbParameter para = cmd.CreateParameter();
            para.ParameterName = parameterName;
            para.Value = value ?? DBNull.Value;
            cmd.Parameters.Add(para);
            return cmd;
        }
        public static DbCommand AddInParameter(this DbCommand cmd, string parameterName, DbType type, int size, object value)
        {
            DbParameter para = cmd.CreateParameter();
            para.ParameterName = parameterName;
            para.DbType = type;
            para.Size = size;
            para.Value = value ?? DBNull.Value;
            cmd.Parameters.Add(para);
            return cmd;
        }

        public static DbCommand AddOutParameter(this DbCommand cmd, string parameterName)
        {
            DbParameter para = cmd.CreateParameter();
            para.ParameterName = parameterName;
            para.Direction = ParameterDirection.Output;
            cmd.Parameters.Add(para);
            return cmd;
        }

        public static DbCommand SetReturnParameter(this DbCommand cmd)
        {
            return cmd.SetReturnParameter(DbType.Int32);
        }
        public static DbCommand SetReturnParameter(this DbCommand cmd, DbType type)
        {
            if (!cmd.Parameters.Contains(DbBase.ReturnParameterName))
            {
                DbParameter para = cmd.CreateParameter();
                para.ParameterName = DbBase.ReturnParameterName;
                para.DbType = type;
                para.Direction = ParameterDirection.ReturnValue;
                cmd.Parameters.Add(para);
            }
            return cmd;
        }
        public static DbParameter GetReturnParameter(this DbCommand cmd)
        {
            int index = cmd.Parameters.IndexOf(DbBase.ReturnParameterName);
            if (index != -1)
            {
                DbParameter returnParameter = cmd.Parameters[index];
                if (returnParameter.Direction == ParameterDirection.ReturnValue)
                {
                    return returnParameter;
                }
            }
            return null;
        }