[英]Entity Framework Creating new data rows during db.SaveChanges()
根據本教程創建AngularJS應用程序: http : //jphoward.wordpress.com/2013/01/04/end-to-end-web-app-in-under-an-hour/
類別:
public class Todo
{
public int ID { get; set; }
public virtual Status Status { get; set; }
}
public class Status
{
public int ID { get; set; }
public string Type { get; set; }
}
功能是單擊按鈕並更改狀態。 單擊該按鈕時,所有正確的內容都將傳遞到Visual Studio中。 最初它根本沒有更新。 經過研究后,我發現了一些強制更改的方法,但是在db.SaveChanges()處,它向Status添加了一個新行,該行具有相同的“類型”,只是最后一個ID的增量ID。
調用update的JS:
Api.Todo.update({ id: todoID }, todo, function () {
$location.path('/');
});
在此功能上打VS:
private DataContext db = new DataContext();
// PUT api/Todo/5
HttpResponseMessage PutTodo(int id, Todo todo)
{
if (!ModelState.IsValid)
{
return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
}
if (id != todo.ID)
{
return Request.CreateResponse(HttpStatusCode.BadRequest);
}
// Found a stack overflow that mentioned that you need to check for things already being tracked
var entry = db.Entry(todo);
if (entry.State == EntityState.Detached)
{
var set = db.Set<Todo>();
Todo attachedEntity = set.Find(todo.ID); // You need to have access to key
if (attachedEntity != null)
{
// The following code does not update any changes to the foreign keys
var attachedEntry = db.Entry(attachedEntity);
attachedEntry.CurrentValues.SetValues(todo);
db.Entry(attachedEntity).State = EntityState.Modified;
// When this didn't work, I tried just changing the status on the already attached entity
//attachedEntity.Status = todo.Status;
//db.SaveChanges();
// However when it hit SaveChanges() it created a new row in the Status table.
}
else
{
//This code was never hit
entry.State = EntityState.Modified; // This should attach entity
}
}
try
{
db.SaveChanges();
}
catch (DbUpdateConcurrencyException ex)
{
return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
}
我的能力已接近尾聲,希望能得到一些幫助或指導。
public class Todo
{
public int ID { get; set; }
//Foreign key
public int StatusID { get; set; } //<====Add this line
public virtual Status Status { get; set; }
}
發布數據時更新外鍵屬性,而不是導航屬性
另外,請檢查以下內容:為什么實體框架將現有對象重新插入到我的數據庫中? http://msdn.microsoft.com/en-us/magazine/dn166926.aspx
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