AddOrUpdate violates unique index - entity-framework

Question

I'm writing an MVC app in ASP.NET with the help of EF and I'm trying to seed my database. I have the following model:
public class Team
{
[ScaffoldColumn(false)]
public int Id { get; set; }
[ForeignKey("ParentTeam")]
public int? ParentTeamId { get; set; }
[Required(ErrorMessage = "Cannot create a Team without a name")]
[Index(IsUnique = true)]
[MaxLength(30)]
public string Name { get; set; }
public IEnumerable<string> Members { get; set; }
public virtual Team ParentTeam { get; set; }
public Team() { }
public Team(string name)
{
Name = name;
}
}
My migration says:
var team = new Team("Admin");
var team2 = new Team("Test Team");
var team3 = new Team("Test Team 2");
context.Teams.AddOrUpdate(t => t.Name, team, team2, team3);
context.SaveChanges();
And then, when I run Update-Database, I get:
System.Data.SqlClient.SqlException: Cannot insert duplicate key row in
object 'dbo.Teams' with unique index 'IX_Name'. The duplicate key
value is (Admin).
It's a little confusing - I thought I told AddOrUpdate to identify rows to update by their names, but this does not happen. I cannot add Name to Team's primary key, because it has a self-referencing foreign key (I could add ParentTeamName as a property, but I don't feel that it should be necessary). Am I misunderstanding the behaviour of AddOrUpdate? Did I specify the condition wrong?

Answer 1

I had the exact same reason. In my case, it was working fine, until I needed to use an Unique Index, when it broke.
My solution was to create a CustomAddOrUpdate method where I try to find the existing instance first based on a Where predicate. If I find it, I just update the properties and if not, it is added to the context.
However, before updating the instance, I had to copy the key values from the original instance to the new instance, to avoid an EF exception telling you cannot change key properties.
Here are the code snippets:
1) First the code in the context class
public void CustomAddOrUpdate<TEntity>(Expression<Func<TEntity, bool>> whereExpression, TEntity entity) where TEntity : class
{
var entitySet = this.EntitySet<TEntity>();
var foundInstance = entitySet.Where(whereExpression).FirstOrDefault();
if (foundInstance != null)
{
CopyKeyProperties<TEntity>(foundInstance, entity);
Entry(foundInstance).CurrentValues.SetValues(entity);
}
else
{
entitySet.Add(entity);
}
}
private void CopyKeyProperties<TEntity>(TEntity source, TEntity target) where TEntity : class
{
string[] keys = this.GetKeyNames<TEntity>();
foreach(var keyName in keys)
{
Entry(target).Property(keyName).CurrentValue = Entry(source).Property(keyName).CurrentValue;
}
}
2) Then on my seed code:
var entityList = new List<MyExempleEntity>()
{
new MyExampleEntity { Prop1 = "a p1", Prop2 = "a p2" },
new MyExampleEntity { Prop1 = "b p1", Prop2 = "b p2" },
new MyExampleEntity { Prop1 = "c p1", Prop2 = "c p2" },
}
foreach(var item in entityList)
{
context.CustomAddOrUpdate<MyExampleEntity>(x => x.Prop1 == item.Prop1 && x.Prop2 == item.Prop2, item);
}
context.SaveChanges()
3) And to wrap up, here you are the code to get the KeyProperties from an entity:
using System.Data.Entity.Core.Metadata.Edm;
using System.Data.Entity.Infrastructure;
using System.Linq;
namespace System.Data.Entity
{
public static class DbContextExtensions
{
public static string[] GetKeyNames<TEntity>(this DbContext context)
where TEntity : class
{
return context.GetKeyNames(typeof(TEntity));
}
public static string[] GetKeyNames(this DbContext context, Type entityType)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
MetadataWorkspace metadata = ((IObjectContextAdapter)context).ObjectContext.MetadataWorkspace;
// Get the mapping between CLR types and metadata OSpace
var objectItemCollection = ((ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace));
// Get metadata for given CLR type
var entityMetadata = metadata
.GetItems<EntityType>(DataSpace.OSpace)
.Single(e => objectItemCollection.GetClrType(e) == entityType);
return entityMetadata.KeyProperties.Select(p => p.Name).ToArray();
}
}
}
The above code was grabbed from this blog:
https://romiller.com/2014/10/07/ef6-1-getting-key-properties-for-an-entity/