数据读取（SQL）与文本写入（fileStream）

要求：从三个不同服务器中取数，对最近10的历史数据进行去重，写出到文本。

1.读取。

public static DataTable ExecuteSql(string connectString, string querySqlString)
        {
            DataTable dt = new DataTable();
            using (SqlConnection conn = new SqlConnection(connectString))
            {
                conn.Open();
                SqlCommand cmd = conn.CreateCommand();
                cmd.CommandText = querySqlString;
                using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
                {
                    adapter.SelectCommand.CommandTimeout = 60 * 30;
                    adapter.Fill(dt);
                    return dt;
                }
            }
        }

当然，另外还有一种，定义了一个我要使用的类型，返回List<T>:

public static List<MarketUrl> GetUrlListFromDataBase(string serverName, string sqlString)
        {
            List<MarketUrl> list = new List<MarketUrl>();
            MarketUrl mu = new MarketUrl();
            string connectStr = ConfigurationManager.ConnectionStrings[serverName].ConnectionString;
            using (SqlConnection conn = new SqlConnection(connectStr))
            {
                conn.Open();
                SqlCommand cmd = conn.CreateCommand();
                cmd.CommandText = sqlString;
                cmd.CommandTimeout = 60 * 30;
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    var dr = new MarketUrl()
                    {
                        market = reader.GetString(reader.GetOrdinal("MarketCode")),
                        url = reader.GetString(reader.GetOrdinal("Url"))
                    };
                    list.Add(dr);
                }
            }
            return list;
        }

2.去重（我的思路是，在取数的时候，对各自的data select 的时候先进行distinct，然后三个data merge到一起时，再次duplicate）：

//colmuns 是distinct的 数组，为columnName
public static DataTable GetDistinctRow(DataTable dt, string[] columns)
        {
            DataView dv = dt.DefaultView;
            DataTable dtDistinct = dv.ToTable(true, columns);
            return dtDistinct;
        }

3.DataRows ConvertTo DataTable

//这是个额外用的到操作，先记下
public static DataTable ConvertToDataTable(DataRow[] rows)
        {
            if (rows == null || rows.Count() < 1)
                return null;
            DataTable dtResult = rows[0].Table.Clone();
            foreach (DataRow r in rows)
            {
                dtResult.Rows.Add(r.ItemArray);
            }
            return dtResult;
        }

4.写入到文本，因code还涉及到别的一些操作，这里只写最简单部分：

StringBuilder sb = new StringBuilder();
foreach (DataRow row in dt.Rows)
{
      sb.AppendLine(dateString + " " + row[0].ToString() + " " + row[1].ToString());
}
using (FileStream fs = new FileStream(filePath, FileMode.Create, FileAccess.Write))
 7 {
     using (TextWriter tw = new StreamWriter(fs, Encoding.Default))
     {
         tw.Write(sb.ToString());
     }
}
File.WriteAllText(logPath, "[" + DateTime.UtcNow + "] Successed...
");