基本用法（CRUD）
1.插入：
// Create entity context
MyTest2Entities mt = new MyTest2Entities(); // Create an instance of SClass
SClass sc = new SClass(); sc.AddTime = DateTime.Now; sc.Name = "Class 1"; // Insert the instance into database
mt.SClasses.Add(sc); int count = mt.SaveChanges(); Console.WriteLine(count.ToString());
2.修改：
// Create entity context
MyTest2Entities mt = new MyTest2Entities(); // Create an instance need modified
SClass sc = new SClass(); sc.Id = 2; sc.Name = "Kyle"; sc.AddTime = DateTime.Now; // Attach the entity need modified
mt.SClasses.Attach(sc); // Modify execute status
mt.Entry(sc).State = System.Data.Entity.EntityState.Modified; mt.SaveChanges();
3.查询：
#region Multiple record query MyTest2Entities 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 query MyTest2Entities 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 DbContext
using (var db = new TestEntities()) { var objectContext = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)db).ObjectContext; // Brand 是其中一个表
ObjectSet<Brand> set = objectContext.CreateObjectSet<Brand>(); //Act
IEnumerable<string> keyNames = set.EntitySet.ElementType.KeyMembers.Select(k => k.Name); Console.WriteLine("{0}", string.Join(",", keyNames.ToArray())); }
转载于:https://www.cnblogs.com/jizhiqiliao/p/10905614.html
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