SqlDataAdapter、DataSet、DataTable使用

原文链接：https://blog.csdn.net/zhang_hui_cs/article/details/7327395

using System.Data;

using System.Data.SqlClient;

//SqlDataAdapter的MSDN网站：http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqldataadapter.aspx

//DataTable的MSDN网站：http://msdn.microsoft.com/en-us/library/system.data.datatable.aspx

//DataSet的MSDN网站: http://msdn.microsoft.com/en-us/library/system.data.dataset.aspx

//DataSets, DataTables, and DataViews (ADO.NET)： http://msdn.microsoft.com/en-us/library/ss7fbaez.aspx

namespace Chapter13

{

class FilterSort

{

static void Main(string[] args)

{

// connection string

string connString = @"

server = .;

integrated security = true;

database = northwind

";

// query 1

string sql1 = @" select      *    from    customers   ; ";

// query 2

string sql2 = @"     select    *   from   products   where     unitprice < 10    ";

// combine queries

string sql = sql1 + sql2;

// create connection

SqlConnection conn = null;

try

{

conn = new SqlConnection(connString);

// create data adapter

SqlDataAdapter da = new SqlDataAdapter(sql, conn);

// create and fill data set

DataSet ds = new DataSet();

/*

* 如果SqlDataAdapter对应的sql语句返回多个数据集，

* 则SqlDataAdapter对应的DataTable名

* 会被依次命名为"Table", "Table1","Table2"……

* 如下调用得到的将会把"Table"对应着"Customers"，

* "Table1"对应着"Products"

*/

da.TableMappings.Add("Table", "Customers");

da.TableMappings.Add("Table1", "Products");

da.Fill(ds);

// get the data tables collection

DataTableCollection dtc = ds.Tables;

//输出DataTableCollection中所有表的表名。

System.Console.WriteLine("DataTable in the DataTableCollection: ");

foreach (DataTable dt in dtc)

{

System.Console.WriteLine("\t{0}", dt.ToString());

}

// display data from first data table

//

// display output header

System.Console.WriteLine("Results from Customers table:");

System.Console.WriteLine(

"CompanyName".PadRight(20) +

"ContactName".PadLeft(23) + "\n");

// set display filter

string fl = "country = 'Germany'";

// set sort

string srt = "companyname asc";

foreach (DataRow row in dtc["Customers"].Select(fl, srt))   //  dtc["Customers"] 是DataTable , 看为内存的一张数据库表 ， 按照条件+排序查询

{

System.Console.WriteLine(

"{0}\t{1}",

row["CompanyName"].ToString().PadRight(25),

row["ContactName"]);

}

// display data from second data table

//

// display output header

System.Console.WriteLine("\n----------------------------");

System.Console.WriteLine("Results from Products table:");

System.Console.WriteLine(

"ProductName".PadRight(20) +

"UnitPrice".PadLeft(21) + "\n");

//下句中dtc["Products"]中还可以按照表索引值访问，等价于dtc[1]

foreach (DataRow row in dtc["Products"].Rows)

{

System.Console.WriteLine("{0}\t{1}",

row["productname"].ToString().PadRight(25),

row["unitprice"]);

}

}

catch (System.Exception e)

{

System.Console.WriteLine("Error: " + e);

}

finally

{

// close connection

conn.Close();

}

}

}

}