context.SaveChanges（）不持久化数据库中的数据

Question

我正在使用MVC应用程序。

当我调用context.SaveChanges来更新特定的记录。更新未在数据库中注册。我也没有得到任何运行时错误。所有通知是我的记录没有更新。我仍然看到相同的值。插入功能完美地工作。

enter code here 

public Admission Update(int stuid){ 

     VDData.VidyaDaanEntities context = new VDData.VidyaDaanEntities(); 
     VDData.Student_Master studentmaster = new VDData.Student_Master(); 

     studentmaster.Student_ID = stuid; 
     studentmaster.Student_First_Name = this.FirstName; 
     studentmaster.Student_Middle_Name = this.MiddleName; 
     studentmaster.Student_Last_Name = this.LastName; 
     studentmaster.Student_Address_1 = this.Address; 
     studentmaster.Student_Address_2 = this.Address2; 
     studentmaster.Student_City = this.City; 
     studentmaster.Student_State = this.State; 
     studentmaster.Student_Pin_Code = this.Pincode; 

     context.SaveChanges(); // here it wont give any kind of error. it runs sucessfully. } 

Answer 1

好像要更新，更换context.SaveChanges();所以你的代码应该是

VDData.Student_Master studentmaster = context.Student_Masters.Single(p=>p.Student_ID == stuid); 

，你不应该改变student_id数据如果是首要的关键。

public Admission Update(int stuid){ 

     VDData.VidyaDaanEntities context = new VDData.VidyaDaanEntities(); 
     //VDData.Student_Master studentmaster = new VDData.Student_Master(); 
//REPLACE WITH 
VDData.Student_Master studentmaster = context.Student_Masters.Where(p=>p.Student_ID == stuid); 

     studentmaster.Student_ID = stuid; 
     studentmaster.Student_First_Name = this.FirstName; 
     studentmaster.Student_Middle_Name = this.MiddleName; 
     studentmaster.Student_Last_Name = this.LastName; 
     studentmaster.Student_Address_1 = this.Address; 
     studentmaster.Student_Address_2 = this.Address2; 
     studentmaster.Student_City = this.City; 
     studentmaster.Student_State = this.State; 
     studentmaster.Student_Pin_Code = this.Pincode; 

     context.SaveChanges(); 

Answer 2

首先得到你所要更新的实体：

var entity = obj.GetEntity(id); 
entity.col1 = "value"; 
context.SaveChanges(entity); 

希望这将有助于。

Answer 3

之前

context.SaveChanges(); 

你需要调用这个

context.Student_Masters.Add(studentmaster); 

编辑：介绍Abstraction您Context class和你的上下文类象下面创建一个方法，那么你可以调用它，每当你想创建或更新你的对象。

public void SaveStudent_Master(Student_Master studentmaster) 
    { 
     using (var context = new VDData.VidyaDaanEntities()) 
     { 
      if (studentmaster.Student_ID == 0) 
      { 
       context.Student_Masters.Add(studentmaster); 
      } 
      else if (studentmaster.Student_ID > 0) 
      { 
       //This Updates N-Level deep Object grapgh 
       //This is important for Updates 
       var currentStudent_Master = context.Student_Masters 
        .Single(s => s.Student_ID == studentmaster.Student_ID); 

       context.Entry(currentStudent_Master).CurrentValues.SetValues(studentmaster);     
      } 
      context.SaveChanges(); 
     } 

然后在你的控制器与_context.SaveStudent_Master(studentmaster);