I recently upgraded my application from ASP.NET MVC 3 and EF 4 to ASP.NET MVC 5 and EF 6. I have several repository functions that I'm using for CRUD functionality.
I haven't changed anything, but I'm suddenly receiving this error if I try to add a record to my entities:
Cannot insert explicit value for identity column in table "Photos" when IDENTITY_INSERT is set to OFF
Here's an example of one of these methods
public void SavePhoto(Photo photo)
{
if (photo.PhotoID == 0) // new photo
_entities.Photos.Add(photo);
else // edit photo
{
_entities.Photos.Attach(photo);
_entities.Entry(photo).State = EntityState.Modified;
}
_entities.SaveChanges();
}
The PhotoID column in my database for this table is set to be the Identity. When this worked before, it would just increment the PhotoID column value based on the last entry (as expected).
Is there a better way to do this now with EF 6?
Is your PhotoId column is "int" type and annotated with "DateGenerated identity"? If so, the following code will error. Because EF might thinking you are inserting 0 into identity column.
if (photo.PhotoID == 0) // new photo
_entities.Photos.Add(photo);
Use id == 0 to check whether it is a new photo or not is not a good practice, actually it is a "bug", because say you have 3 records in the system(which default could mean your photoid is not greater than 4), And somehow you PhotoID was manipulated as 100 in the backend, now when your code run, your code will set its state as Modified. And EF might throw error for you, or EF might try to insert it for you instead of editing.
So I would suggest to use follow code
var photo = _entities.Photos.Find(photo.PhotoId)
if (photo == null) {
//your code to add photo
}
else
{
//your code to set the the modal state to modified.
}
Related
I have a very simple row that I'm inserting using Entity, which I do like so:
var context = GetEntityContext();
SOMEPOCO newobj = new SOMEPOCO
{
Data = data
};
context.SOMEOBJECTS.Add(newobj);
context.SaveChanges();
return newobj.ID;
And newobj.ID (the auto-incremented primary key) is indeed populated. No errors are raised or exceptions thrown. But when I go to SQL Management Studio and query for items or look it up in code, it doesn't show up. But if I manually make an entry in the DB, it increments the primary key as though the previous failed entry were there.
What could be causing this?
Thanks.
I am using ASP.NET MVC2 in Visual Studio 2008. I believe the SQL Server is 2005.
I have two tables: EquipmentInventory and EquipmentRequested
EquipmentInventory has a primary key
of sCode
EquipmentRequested has a
foreign key called sCode based upon
sCode in EquipmentInventory.
I am trying the following code (lots of non-relevent code removed):
try
{
EChODatabaseConnection myDB = new EChODatabaseConnection();
//this section of code works fine. The data shows up in the database as expected
foreach (var equip in oldData.RequestList)
{
if (equip.iCount > 0)
{
dbEquipmentInventory dumbEquip = new dbEquipmentInventory();
dumbEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
myDB.AddTodbEquipmentInventorySet(dumbEquip);
}
}
myDB.SaveChanges(); //save this out immediately so we can add in new requests
//this code runs fine
foreach (var equip in oldData.RequestList)
{
if (equip.iCount > 0)
{
dbEquipmentRequested reqEquip = new dbEquipmentRequested();
reqEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
myDB.AddTodbEquipmentRequestedSet(reqEquip);
}
}
//but when I try to save the above result, I get an error
myDB.SaveChanges();
oldData is passed into the function. newRequest is the result of adding to a "non-related" table. newRequest.iRequestID does have a value.
In looking at the reqEquip is the watch window, I do notice that EquipInventory is null.
The error message I receive is:
"Entities in 'EChODatabaseConnection.dbEquipmentRequestedSet' participate in the 'FK_EquipmentRequested_EquipmentInventory_sCode' relationship. 0 related 'EquipmentInventory' were found. 1 'EquipmentInventory' is expected."
Obviously I'm doing something wrong but thus far, I can not seem to find where I am having a problem.
Anyone have some hints on how to properly insert a record into a table that has a foreign key reference?
UPDATE:
I am using the Data Entity Framework.
UPDATE:
Thanks to Rob's answer, I was able to figure out my error.
As Rob mentioned, I needed to set my reference for the foreign key.
My coding result looks like:
foreach (var equip in oldData.RequestList)
{
if (equip.iCount > 0)
{
dbEquipmentInventory dumbEquip = new dbEquipmentInventory();
dumbEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
myDB.AddTodbEquipmentInventorySet(dumbEquip);
//add in our actual request items
dbEquipmentRequested reqEquip = new dbEquipmentRequested();
reqEquip.EquipmentInventory = dumbEquip;
myDB.AddTodbEquipmentRequestedSet(reqEquip);
}
}
myDB.SaveChanges();
Does anyone see a better method for doing this?
What are you using as an ORM? I believe that regardless of which one you're using, you could use the foreign key handling of most ORMs to handle this for you. For example, you make a new dumbEquip, don't do the immediate save. Do your dbEquipmentRequested reqEquip = new dbEquipmentRequested(); and add the data to it and then say dumbEquip.dbEquipmentRequested.Add(reqEquip). Then save the record and the ORM should save the records in the correct order required for the FK and even enter the FK ID into the reqEquip record.
i want to make sure all product names are unique so i tried to do the following.
but it is causing an infinity loop at the lambda expression.
public partial class Product
{
partial void OnProductNameChanging(string value)
{
using(var ctx = new MyEntityContext()){
var val = value;
var item = ctx.Products.Where(o=>o.ProductName == val).FirstOrDefault();
if(item != null)
throw new ValidationException("Product Name existed.");
}
}
}
i'm using asp.net 4.0 with dynamic data and entity framework.
Why don't you set it up on database level and handle exeption in case if product name already exists?
I am not too familiar with EF, but you should get the changeset and compare values. That is, for the Product Entity and in the case of the the changeset having an Update, compare the EXISTING value with NEW, and change the new in the case of duplication.
Here's how to get changeSet in EF :
http://davidhayden.com/blog/dave/archive/2005/11/16/2570.aspx
the comparison and value must be called before any context.SubmitChanges();
Hope this helps.
So I'm starting out with EF on my website (C#) and Ive run into a bit of a snag. A user can either create or modify data and they will do that with the selection screen (page 1). If a user selects to create new data, I will perform the following code:
Program newProg = new Program();
using (DatabaseEntities context = new DatabaseEntities())
{
Guid id = new Guid(list.SelectedValue);
var itemString = from item in context.Set where item.Id == id select item;
Item selectedItem = itemString.ToList()[0];
newProg.Items.Add(selectedItem);
context.AddToProgramSet(newProg);
context.Detach(newProg);
}
Pretty much creating a new instance of the 'Program' which will be passed along each user control until the user is ready to submit to the database. At that point the following code will be executed:
using (DatabaseEntities context = new DatabaseEntities())
{
context.AddToProgramSet(this.SummaryControl.SelectedProgram);
context.SaveChanges();
}
Unfortunately when I get there, I receive the following message:
The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key.
at this line:
context.AddToProgramSet(this.SummaryControl.SelectedProgram);
Also, when I add the following line prior to the previous:
context.Attach(this.SummaryControl.SelectedProgram);
I get this error:
An object with a null EntityKey value cannot be attached to an object context.
Any help would be greatly appreciated. Thanks.
The root cause of this error is that you are attempting to add an Entity as a new Entity that already has its primary key set.
At what point do you add the Entities to your SummaryControl? Your first code snippet shows you adding the Entity:
...
newProg.Items.Add(selectedItem);
context.AddToProgramSet(newProg);
context.Detach(newProg);
...
Then you appear to add it again:
using (DatabaseEntities context = new DatabaseEntities())
{
context.AddToProgramSet(this.SummaryControl.SelectedProgram);
context.SaveChanges();
}
If newProg and this.SummaryControl.SelectedProgram are the same Entity, you've attempted to add it twice. Remove the context.AddToProgramSet(newProg); from the first snippet, do you work on the Entity, then add it to the ProgramSet.
Dave is right that the root cause is that the entity already has a primary key.
One thing that you do not show in your code is how:
Program newProg = new Program();
Becomes:
this.SummaryControl.SelectedProgram
One way that you could fix it is by saving newProg to the database before you start adding Items to it.
I have an asp.net site which uses the ASP.net Membership provider. Each comment, entry etc in the DB is tracked by the userID.
Since MS doesn't provide a way to change the username, I've found the userNAME in the "users" table in the DB and there is only 1 place where the username appears.
My question is,
Is it safe to provide an "edit profile" page where the user is allowed to edit their own username. Of course i would handle this change in the background by directly changing the "username" value in the DB.
Are there any downsides to this ? I've created and modified some test accounts and it seems to be fine, i am just wondering if there is any known negatives to this before putting it into production.
cptScarlet's link was good, however I despise using stored procedures if I don't have to and I favor Entity Framework whenever possible. Here's what I did to change the user name, using EF 4.0 and .NET 4.0:
Right click project -> Add New Item -> ADO.NET Entity Data Model
Give it a proper name, I chose "MembershipModel.edmx" and click Add
Select Generate from database and click Next
Add the connection to your 'aspnetdb' database (the ASP.NET membership database)
Give it a proper name, I chose "MembershipEntities"
Click Next
Drill into Tables and select aspnet_Users
Change the Model Namespace to MembershipModel
Click Finish
Now you can add code to create the EF object context and modify the database:
public void ChangeUserName(string currentUserName, string newUserName)
{
using (var context = new MembershipEntities())
{
// Get the membership record from the database
var currentUserNameLowered = currentUserName.ToLower();
var membershipUser = context.aspnet_Users
.Where(u => u.LoweredUserName == currentUserNameLowered)
.FirstOrDefault();
if (membershipUser != null)
{
// Ensure that the new user name is not already being used
string newUserNameLowered = newUserName.ToLower();
if (!context.aspnet_Users.Any(u => u.LoweredUserName == newUserNameLowered))
{
membershipUser.UserName = newUserName;
membershipUser.LoweredUserName = newUserNameLowered;
context.SaveChanges();
}
}
}
}
Note: I did not account for application ID's in my code. I typically only ever have one application using the ASP.NET membership database, so if you have multiple apps, you'll need to account for that.