1.linq to string

string s2 = "abc";

var data2 = s2.Where(x => x.CompareTo('a') > 0).ToList();

string s3 = "";

data2.ForEach(a => { s3 += a.ToString(); });

2. linq to datatable

using System;

using System.Collections.Generic;

using System.Data;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace ConsoleApplication8

{

public class Student

{

public int No { get; set; }

public string Name { get; set; }

public int Age { get; set; }

}

class Program

{

static void Main(string[] args)

{

//TestDb2Entities1 DbContext = new TestDb2Entities1();

//var stu = (from s in DbContext.UserInfoSets where s.Id == 1 select s).First();

//RoleInfoSet r = stu.RoleInfoSets.ToList()[0];

//DataTable table=new DataTable();

//var t = from s in table.AsEnumerable() group s by s.Field<Int32>("") into g select g;

DataTable table = new DataTable();

table.Columns.Add("Id", typeof(Int32));

table.Columns.Add("Name", typeof(String));

table.Columns.Add("Age", typeof(Int32));

DataRow row = table.NewRow();

row["Id"] = 1;

row["Name"] = "1";

row["Age"] = 10;

table.Rows.Add(row);

row = table.NewRow();

row["Id"] = 2;

row["Name"] = "2";

row["Age"] = 2;

table.Rows.Add(row);

row = table.NewRow();

row["Id"] = 1;

row["Name"] = "3";

row["Age"] = 3;

table.Rows.Add(row);

//var stus = from s in table.AsEnumerable() group s by s.Field<Int32>("Id") into g select

//new {

// key=g.Key,value=g

//}

//;

var stus = from s in table.AsEnumerable()

where s.Field<Int32>("Id") == 1

group s by s.Field<Int32>("Id")

into g

select g;

var list = stus.ToList();

var c = list[0].ToList()[1].Field<Int32>("Age");

Console.ReadKey();

}

}

}

3.待续