Ado.net 创建DataTable

  /// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name="SQLString">查询语句</param>
        /// <returns>DataSet</returns>
        public   DataSet Query(string SQLString, params SqlParameter[] cmdParms)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                SqlCommand cmd = new SqlCommand();
                PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataSet ds = new DataSet();
                    try
                    {
                        da.Fill(ds, "ds");
                        cmd.Parameters.Clear();
                    }
                    catch (System.Data.SqlClient.SqlException ex)
                    {
                        throw new Exception(ex.Message);
                    }
                    return ds;
                }
            }
        }
        private   void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, string cmdText, SqlParameter[] cmdParms)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            if (trans != null)
                cmd.Transaction = trans;
            cmd.CommandType = CommandType.Text;//cmdType;
            if (cmdParms != null)
            {
                foreach (SqlParameter parameter in cmdParms)
                {
                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&
                        (parameter.Value == null))
                    {
                        parameter.Value = DBNull.Value;
                    }
                    cmd.Parameters.Add(parameter);
                }
            }
        }
 
 string connectionString = "Data Source=192.168.42.97;Initial Catalog=DataCompare;User ID=sa;Password=sa";
        public DataTable QueryBigFQCY(string datatype)
        {
            string cmdText = "select   distinct pici from InputData  where and createtime >='2011-09-27 10:40:54.293' order by pici desc";
            DataTable dt = new DataTable();
            SqlParameter[] parm = new SqlParameter[] { new SqlParameter("@datetype", datatype) };
            try
            {
                DataSet ds = Query(cmdText, parm);
                if (ds != null && ds.Tables.Count > 0)
                {
                    dt = ds.Tables[0];
                }
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            return dt;
        }