We are using EF 4.0 for performing database operation. we are using following code to save products to database :
public void SaveProduct(Product updatedProduct)
{
using (model)
{
Product originalProduct = model.Products.Single(p => p.ProductID == updatedProduct.ProductID);
if(originalProduct.Any())
{
model.Products.ApplyCurrentValues(updatedProduct);
}
else
{
model.Products.Attach(updatedProdut);
}
model.SaveChanges();
}
}
But while attaching a product, I am getting following error :
An object with the same key already exists in the ObjectStateManager.
The ObjectStateManager cannot track multiple objects with the same
key.
Im a little surprised by the code. Would not work in EF6.
Anyway:
Single returns 1 entry or Exception if not found.
EF 4.x had SingleOrDefault, which returns a null if not found.
IEnumerable.Single extension returns T.
Are you sure T supports Any().?
Clearly the error is you cant put the record in to the context twice.
If the single worked but Any() test didnt, that might explain.
See SingleOrDefault.
Consider test for Null instead of any.
Related
I have a method that receives an IEnumerable<Guid> of IDs to objects I want to delete. One suggested method is as follows
foreach(Guid id in ids)
{
var tempInstance = new MyEntity { Id = id };
DataContext.Attach(tempInstance); // Exception here
DataContext.Remove(tempInstance);
}
This works fine if the objects aren't already loaded into memory. But my problem is that when they are already loaded then the Attach method throws an InvalidOperationException - The instance of entity type 'MyEntity' cannot be tracked because another instance with the key value 'Id:...' is already being tracked. The same happens if I use DataContext.Remove without calling Attach.
foreach(Guid id in ids)
{
var tempInstance = new MyEntity { Id = id };
DataContext.Remove(tempInstance); // Exception here
}
I don't want to use DataContext.Find to grab the instance of an already loaded object because that will load the object into memory if it isn't already loaded.
I cannot use DataContext.ChangeTracker to find already loaded objects because only objects with modified state appear in there and my objects might be loaded and unmodified.
The following approach throws the same InvalidOperationException when setting EntityEntry.State, even when I override GetHashCode and Equals on MyEntity to ensure dictionary lookups see them as the same object.
foreach(Guid id in ids)
{
var tempInstance = new MyEntity { Id = id };
EntityEntry entry = DataContext.Entry(tempInstance);
entry.State == EntityState.Deleted; // Exception here
}
The only way so far I have found that I can achieve deleting objects by ID without knowing if the object is the following:
foreach(Guid id in ids)
{
var tempInstance = new MyEntity { Id = id };
try
{
DataContext.Attach(tempInstance); // Exception here
}
catch (InvalidOperationException)
{
}
DataContext.Remove(tempInstance);
}
It's odd that I am able to call DataContext.Remove(tempInstance) without error after experiencing an exception trying to Attach it, but at this point it does work without an exception and also deletes the correct rows from the database when DataContext.SaveChanges is executed.
I don't like catching the exception. Is there a "good" way of achieving what I want?
Note: If the class has a self-reference then you need to load the objects into memory so EntityFrameworkCore can determine in which order to delete the objects.
Strangely, although this is a quite common exception in EF6 and EF Core, neither of them expose publicly a method for programmatically detecting the already tracked entity instance with the same key. Note that overriding GetHashCode and Equals doesn't help since EF is using reference equality for tracking entity instances.
Of course it can be obtained from the DbSet<T>.Local property, but it would not be as efficient as the internal EF mechanism used by Find and the methods throwing the aforementioned exception. All we need is the first part of the Find method and returning null when not found instead of loading from the database.
Luckily, for EF Core the method that we need can be implemented relatively easily by using some of the EF Core internals (under the standard This API supports the Entity Framework Core infrastructure and is not intended to be used directly from your code. This API may change or be removed in future releases. policy). Here is the sample implementation, tested on EF Core 2.0.1:
using Microsoft.EntityFrameworkCore.Internal;
namespace Microsoft.EntityFrameworkCore
{
public static partial class CustomExtensions
{
public static TEntity FindTracked<TEntity>(this DbContext context, params object[] keyValues)
where TEntity : class
{
var entityType = context.Model.FindEntityType(typeof(TEntity));
var key = entityType.FindPrimaryKey();
var stateManager = context.GetDependencies().StateManager;
var entry = stateManager.TryGetEntry(key, keyValues);
return entry?.Entity as TEntity;
}
}
}
Now you can use simply:
foreach (var id in ids)
DataContext.Remove(DataContext.FindTracked<MyEntity>(id) ?? new MyEntity { Id = id }));
or
DataContext.RemoveRange(ids.Select(id =>
DataContext.FindTracked<MyEntity>(id) ?? new MyEntity { Id = id }));
I have a complex and big object graph that I want to insert in database by using a DbContext and SaveChanges method.
This object is a result of parsing a text file with 40k lines (around 3MB of data). Some collections inside this object have thousands of items.
I am able to parse the file correctly and add it to the context so that it can start tracking the object. But when I try to SaveChanges, it says:
Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.SqlClient.SqlException: String or binary data would be truncated.
I would like to know if there is a smart and efficient way of discovering which object is causing the issue. It seems that a varchar field is too little to store the data. But it's a lot of tables and fields to check manually.
I would like to get a more specific error somehow. I already configured an ILoggerProvider and added the EnableSensitiveDataLogging option in my dbContext to be able to see which sql queries are being generated. I even added MiniProfiler to be able to see the parameter values, because they are not present in the log generated by the dbContext.
Reading somewhere in the web, I found out that in EF6 there is some validation that happens before the sql is passed to the database to be executed. But it seems that in EF Core this is not available anymore. So how can I solve this?
After some research, the only approach I've found to solve this, is implementing some validation by overriding dbContext's SaveChanges method. I've made a merge of these two approaches to build mine:
Implementing Missing Features in Entity Framework Core - Part 3
Validation in EF Core
The result is...
ApplicationDbContext.cs
public override int SaveChanges(bool acceptAllChangesOnSuccess)
{
ValidateEntities();
return base.SaveChanges(acceptAllChangesOnSuccess);
}
public override async Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = new CancellationToken())
{
ValidateEntities();
return await base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
}
private void ValidateEntities()
{
var serviceProvider = this.GetService<IServiceProvider>();
var items = new Dictionary<object, object>();
var entities = from entry in ChangeTracker.Entries()
where entry.State == EntityState.Added || entry.State == EntityState.Modified
select entry.Entity;
foreach (var entity in entities)
{
var context = new ValidationContext(entity, serviceProvider, items);
var results = new List<ValidationResult>();
if (Validator.TryValidateObject(entity, context, results, true)) continue;
foreach (var result in results)
{
if (result == ValidationResult.Success) continue;
var errorMessage = $"{entity.GetType().Name}: {result.ErrorMessage}";
throw new ValidationException(errorMessage);
}
}
}
Note that it's not necessary to override the other SaveChanges overloads, because they call these two.
The Error tells you that youre writing more characters to a field than it can hold.
This error for example would be thrown when you create a given field as NVARCHAR(4) or CHAR(4) and write 'hello' to it.
So you could simply check the length of the values you read in to find the one which is causing your problem. There is at least on which is too long for a field.
I am inserting data into a table for an integration test using Entity Framework 6. When I execute the following code, I get a DbUpdateConcurrencyException on the call to SaveChanges().
using (var context = new CONTACTEntities())
{
context.Facilities.AddRange(facilities);
context.SaveChanges();
}
I'm not sure why this is happening. The table should be empty since the tables are dropped/created before the test runs and this is the only place in the test that I insert any data into this table. Any ideas?
If you are using SQLServer and you have a datetime column in your table, change the columns type to datetime2(7).
It sounds strange but it works. The explanation is something about milliseconds.
You must be aware of how Entity Framework handle keys in your table. In my code I set the HasDatabaseGeneratedOption. It can be otherwise in your code.
public class IceCatCategoryMap : EntityTypeConfiguration<IceCatCategory>
{
public IceCatCategoryMap()
{
ToTable("SemlerServices_IceCatCategory");
HasKey(m => m.Id);
Property(m => m.Id).IsRequired().HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
Can u tell me what is the problem?
If you are using two different instances of the DbContext (the db variable as you named it) then nothing will be saved when you call SaveChanges on a context different than the one where your entities are tracked. You need to use the Attach method first.
db.customer_images.Attach(item);
db.SaveChanges();
However I think in your case you can avoid the attach step if you refactor a bit you code and don't use the DbContext from the entity itself.
Before going through my answer, you must check, if you are attaching the item as shown in excepted answer or check this code:.
if (dbStudentDetails != null && dbStudentDetails.Id != 0)
{
// update scenario
item.Id = dbStudentDetails.Id;
_context.Entry(dbStudentDetails).CurrentValues.SetValues(item);
_context.Entry(dbStudentDetails).State = EntityState.Modified;
}
else
{
// create scenario
_context.StudentDetails.Add(item);
}
await _context.SaveChangesAsync();
If above solution doesn't work, then check the below answer.
Saw a very wired issue, and thought to must answer this. as this can
be a major issue if you have lots of constraints and indexes in your
SQL.
db.SaveChanges() wasn't throwing any error, but not working (I have tried Exception or SqlException). This was not working because the Unique constraint was not defined properly while creating the Entity Models.
How you can Identified the issue:
I connected my SQL Server and opened the SQL Profiler.
Just before the db.SaveChanges(), I cleared all my profiler logs and ran the db.SaveChanges(). It logged the statement. I copied the script from the profiler and ran the script in SQL Server.
And bingo, I can see the actual error, which is being thrown at SQL Server side.
(images: have some hints, how you can get the execute statement from Profiler and run on sql server)
What you can do For Entity Framework Core:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Students>().HasIndex(p => new { p.RollNumber, p.PhoneNumber }).IsUnique(true).IsClustered(false).HasDatabaseName("IX_Students_Numbers");
}
What you can do For Entity Framework 6 and below:
using System.Data.Entity.ModelConfiguration;
internal partial class StudentsConfiguration : EntityTypeConfiguration<Students>
{
public StudentsConfiguration()
{
HasIndex(p => new { p.RollNumber, p.PhoneNumber }).IsUnique(true).IsClustered(false).HasName("IX_Students_Numbers");
}
}
Try to query your entity by Id, eg:
entity = this.repo.GetById(item.id);
entity.is_front = false;
if (dbSaveChanges() > 0)
{
....
}
I have an Entity Framework v1 project. I have two entities (Roles and Permissions), which have a many-to-many relationship with each other. I pass in a object to be saved (through a WCF call, I do not create it from a context myself), which has new entries in the many-to-many relationship.
I use "context.ApplyPropertyChanges" to update the record with the new properties. I know that this does not update relationships though. I attempt to either do a ChildCollection.Add(relatedObject); or ChildCollection.Attach(relatedObject).
When I use the "Add" method, I get the error that: 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.
When I use the "Attach" method, I get the error that: 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.
I am getting quite frustrated, and I think I can hear the Entity Framework laughing at me.
Does anyone know how I can resolve this?
MyRole x = context.Roles.FirstOrDefault(a => a.RoleId == this.RoleId);
context.ApplyPropertyChanges("Roles", this);
foreach (MyPermission p in this.Permissions)
{
x.Permissions.Add(p);
// ^ or v
x.Permissions.Attach(p);
}
context.SaveChanges();
Thanks.
Wow. After 20 or so straight hours on this problem, I'm starting to hate the Entity Framework. Here is the code that appears to be working currently. I would appreciate any advice on how to make this more streamlined.
I did rework the WCF service so that there is only the one data context. Thanks Craig.
Then I had to change the code to the following:
MyRole x = context.Roles.FirstOrDefault(a => a.RoleId == this.RoleId);
if (x == null) // inserting
{
MyApplication t = this.Application;
this.Application = null;
context.Attach(t);
this.Application = t;
}
else // updating
{
context.ApplyPropertyChanges("Roles", this);
x.Permissions.Load();
IEnumerable<Guid> oldPerms = x.Permissions.Select(y => y.PermissionId);
List<MyPermission> newPerms = this.Permissions.Where(y => !oldPerms.Contains(y.PermissionId)).ToList();
IEnumerable<Guid> curPerms = this.Permissions.Select(y => y.PermissionId);
List<MyPermission> deletedPerms = x.Permissions.Where(y => !curPerms.Contains(y.PermissionId)).ToList();
// new
foreach (MyPermission p in newPerms)
{
x.Permissions.Add(context.Permissions.First(z => z.PermissionId == p.PermissionId));
}
// deleted
foreach (MyPermission p in deletedPerms)
{
x.Permissions.Remove(context.Permissions.First(z => z.PermissionId == p.PermissionId));
}
}
You are using multiple ObjectContexts concurrently (the variable context and whereever this came from). Don't do that. It will only make things very difficult for you. Use one ObjectContext at a time.
I can give more specific advice if you show more code.
I suspect you are getting the errors because the ObjectContext thinks you are trying to add a new entity but finds it already has a EntityKey. I use the AttachTo method of the ObjectContext to attach my already existing entities to their EntitySet. I have had results generating my entities from stubs or hitting the database. This way when you add the entity to the navigation property on your entity, the ObjectContext finds the entity in it's EntitySet and knows it is an existing entity and not a new one. I don't know if this is clear. I could post some code if it would help. As Mr Stuntz said in his answer, posting more of your code would help.