DataTable与Linq相互转换方法

var query1 =
from stu in dtStu.AsEnumerable( )
from score in dtScore.AsEnumerable( )
where stu.Field<int>("ScoreID") == score.Field<int>("ScoreID")
where (int)stu["Age"] > 20
select stu;
//通过CopyToDataTable()方法创建新的副本
DataTable newDt = query1.CopyToDataTable<DataRow>( );

namespace UseCopyToTable
{
class Program
{
static void Main(string[] args)
{
UseCopyToDTSimple( );
UseSetField( );
}

static DataSet BuildDataSet( )
{
//创建Students数据集
DataSet ds = new DataSet("Students");
//创建Students数据表，并添加到数据集
//Students数据表包含学生信息
DataTable dtStu = new DataTable("Students");
ds.Tables.Add(dtStu);
//添加学生信息记录的列信息
dtStu.Columns.AddRange(new DataColumn[]{
new DataColumn("Name", Type.GetType("System.String")),
new DataColumn("XingBie", Type.GetType("System.String")),
new DataColumn("Age", Type.GetType("System.Int32")),
new DataColumn("ScoreID", Type.GetType("System.Int32")),
});
//添加学生信息的行信息
dtStu.Rows.Add("张三", "男", 20, 1);
dtStu.Rows.Add("李四", "男", 19, 2);
dtStu.Rows.Add("王霞", "女", 21, 3);
dtStu.Rows.Add("赵敏", "女", 22, 4);
dtStu.Rows.Add("吴安", "男", 18, 5);
//创建Scores数据表，并添加到数据集
//Scores数据表包含学生成绩记录
DataTable dtScore = new DataTable("Scores");
ds.Tables.Add(dtScore);
//添加成绩记录的列信息
dtScore.Columns.AddRange(new DataColumn[]{
new DataColumn("ScoreID", Type.GetType("System.Int32")),
new DataColumn("Math", Type.GetType("System.Int32")),
new DataColumn("Chinese", Type.GetType("System.Int32")),
new DataColumn("English", Type.GetType("System.Int32")),
});
//添加学生成绩记录
dtScore.Rows.Add(1, 80, 75, 78);
dtScore.Rows.Add(3, 88, 80, 60);
dtScore.Rows.Add(4, 75, 90, 80);
dtScore.Rows.Add(5, 59, 80, 75);
//返回数据集
return ds;
}

static void UseCopyToDTSimple( )
{
//获取数据集和要进行查询的数据表
DataSet ds = BuildDataSet( );
DataTable dtStu = ds.Tables["Students"];
DataTable dtScore = ds.Tables["Scores"];
//查询query1年龄大于20且具有成绩的学生
var query1 =
from stu in dtStu.AsEnumerable( )
from score in dtScore.AsEnumerable( )
where stu.Field<int>("ScoreID") == score.Field<int>("ScoreID")
where (int)stu["Age"] > 20
select stu;
//通过CopyToDataTable()方法创建新的副本
DataTable newDt = query1.CopyToDataTable<DataRow>( );
//打印副本的信息
System.Console.WriteLine("学生列表：");
foreach (var item in newDt.AsEnumerable())
{
System.Console.WriteLine("姓名:{0}, 性别:{1}， 年龄:{2}",
item["Name"], item["XingBie"], item["Age"]);
}
}

static void UseSetField( )
{
//获取数据集和要进行查询的数据表
DataSet ds = BuildDataSet( );
DataTable dtStu = ds.Tables["Students"];
//将所有学生的年龄都增加2岁
foreach (var row in dtStu.AsEnumerable())
{
int age = row.Field<int>("Age");
row.SetField<int>("Age", age + 2);
}
//打印新的学生信息
System.Console.WriteLine("学生列表：");
foreach (var item in dtStu.AsEnumerable( ))
{
System.Console.WriteLine("姓名:{0}, 性别:{1}， 年龄:{2}",
item["Name"], item["XingBie"], item["Age"]);
}
}
}
}