context.SaveChanges（）不持久化數據庫中的數據

Question

我正在使用MVC應用程序。

當我調用context.SaveChanges來更新特定的記錄。更新未在數據庫中註冊。我也沒有得到任何運行時錯誤。所有通知是我的記錄沒有更新。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，更換context.SaveChanges();所以你的代碼應該是

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

，你不應該改變student_id數據如果是首要的關鍵。

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實體：

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

希望這將有助於。

Answer 3

之前

context.SaveChanges(); 

你需要調用這個

context.Student_Masters.Add(studentmaster); 

編輯：介紹Abstraction您Context class和你的上下文類象下面創建一個方法，那麼你可以調用它，每當你想創建或更新你的對象。

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(); 
     } 

然後在你的控制器與_context.SaveStudent_Master(studentmaster);