linq to datatable 和lambda查询datatable

static DataTable table = new DataTable();
static DataColumn dc = new DataColumn();
static void Main()
{
Createtable();
table.Rows.Add(1, 2,"2010-1-1");
table.Rows.Add(2, 3, "2010-1-1");
table.Rows.Add(3, 4, "2010-1-1");
table.Rows.Add(4, 5, "2010-1-1");
table.Rows.Add(5, 2, "2010-1-2");
table.Rows.Add(6, 3, "2010-1-2");
table.Rows.Add(7, 4, "2010-1-2");
table.Rows.Add(8, 5, "2010-1-2");

var query = from dt in table.AsEnumerable()
where new int[] { 2, 3, 4 }.Contains(dt.Field<Int32>("PID"))
orderby dt.Field<DateTime>("CreateDate") descending
group dt by dt.Field<Int32>("PID") into g
let n = (from d in g.Take(2).Skip(1) select d).FirstOrDefault()
select new
{
ID = n.Field<Int32>("ID"),
PID = g.Key,
CreateDate = n.Field<DateTime>("CreateDate")
};
query.ToList().ForEach(m => Console.WriteLine("{0}\t{1}\t{2}\t",m.ID,m.PID,m.CreateDate));
}
public static void Createtable()
{
dc = new DataColumn("ID", Type.GetType("System.Int32"));
table.Columns.Add(dc);
dc = new DataColumn("PID", Type.GetType("System.Int32"));
table.Columns.Add(dc);
dc = new DataColumn("CreateDate", Type.GetType("System.DateTime"));
table.Columns.Add(dc);
}

DataTable dt = new DataTable();
DataColumn dc = new DataColumn("UserName", System.Type.GetType("System.String"));
DataColumn dc1 = new DataColumn("UserPwd", System.Type.GetType("System.String"));
dt.Columns.Add(dc);
dt.Columns.Add(dc1);
DataRow dr = dt.NewRow();
dr["UserName"] = "22";
dr["UserPwd"] = "33";
dt.Rows.Add(dr);

var rownumber = dt.AsEnumerable().Where<DataRow>(C=>C["UserName"].ToString()=="22");
int row = rownumber.Count<DataRow>();
foreach ( DataRow en in  rownumber)
{

Response.Write("User" + en["UserName"] + "pwd" + en["UserPwd"]);
}