基本用法（CRUD）

1.插入：

// Create entity contextMyTest2Entities mt = new MyTest2Entities();// Create an instance of SClassSClass sc = new SClass();sc.AddTime = DateTime.Now;sc.Name = "Class 1";// Insert the instance into databasemt.SClasses.Add(sc);int count = mt.SaveChanges();Console.WriteLine(count.ToString());

2.修改：

// Create entity contextMyTest2Entities mt = new MyTest2Entities();// Create an instance need modifiedSClass sc = new SClass();sc.Id = 2;sc.Name = "Kyle";sc.AddTime = DateTime.Now;// Attach the entity need modifiedmt.SClasses.Attach(sc);// Modify execute statusmt.Entry(sc).State = System.Data.Entity.EntityState.Modified;mt.SaveChanges();

3.查询：

#region Multiple record queryMyTest2Entities mt = new MyTest2Entities();var classes = from c in mt.SClasses                where c.Id < 10                select c;foreach (var item in classes){    Console.WriteLine(item.Name);}#endregion#region Single record queryMyTest2Entities mt = new MyTest2Entities();var single = (from c in mt.SClasses                where c.Id == 1                select c).FirstOrDefault();if (single != null)    Console.WriteLine(single.Name);#endregion

4.删除：

MyTest2Entities mt = new MyTest2Entities();SClass sc = new SClass();sc.Id = 2;mt.SClasses.Attach(sc);mt.Entry(sc).State = System.Data.Entity.EntityState.Deleted;mt.SaveChanges();

获取主键：

// TestEntities 继承于 DbContextusing (var db = new TestEntities()){    var objectContext = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)db).ObjectContext;    // Brand 是其中一个表    ObjectSet
     
       set = objectContext.CreateObjectSet
      
       ();    //Act    IEnumerable
       
         keyNames = set.EntitySet.ElementType.KeyMembers.Select(k => k.Name);    Console.WriteLine("{0}", string.Join(",", keyNames.ToArray()));}