Value Conversion of custom struct type throws exception if it doesn't implement == and != operators

[gojanpaolo]

Exception message: 

The binary operator Equal is not defined for the types 'ExceptionEqualIsNotDefined.Fuel' and 'ExceptionEqualIsNotDefined.Fuel'.

Stack trace:

   at Microsoft.EntityFrameworkCore.Metadata.Internal.ClrAccessorFactory`1.Create(PropertyInfo propertyInfo, IPropertyBase propertyBase)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.ClrAccessorFactory`1.Create(IPropertyBase property)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.<>c.<get_Getter>b__34_0(PropertyBase p)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.get_Getter()
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.ReadPropertyValue(IPropertyBase propertyBase)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.ChangeDetector.DetectChanges(InternalEntityEntry entry)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.ChangeDetector.DetectChanges(IStateManager stateManager)
   at Microsoft.EntityFrameworkCore.ChangeTracking.ChangeTracker.DetectChanges()
   at Microsoft.EntityFrameworkCore.DbContext.TryDetectChanges()
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges()
   at ExceptionEqualIsNotDefined.Tests.Test() in 

Steps to reproduce

public class Tests
{
    [Fact]
    public void Test()
    {
        using (var connection = new SqliteConnection("DataSource=:memory:"))
        {
            connection.Open();

            var options = new DbContextOptionsBuilder<Context>()
                .UseSqlite(connection)
                .Options;

            using (var context = new Context(options))
            {
                context.Database.EnsureCreated();
            }

            using (var context = new Context(options))
            {
                context.Add(new Load());
                context.SaveChanges(); //throws exception here
            }
        }
    }
}

public class Context : DbContext
{
    public Context(DbContextOptions options) : base(options) { }

    public DbSet<Load> Load { get; private set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Load>(e =>
        {
            e.Property(l => l.Fuel)
                .HasConversion(
                    f => f.Volume,
                    v => new Fuel(v));
        });
    }
}

public class Load
{
    public int LoadId { get; private set; }

    public Fuel Fuel { get; set; }
}

public struct Fuel
{
    public Fuel(double volume)
    {
        Volume = volume;
    }

    public double Volume { get; }

    // Uncomment below to get rid of exception.
    //public static bool operator ==(Fuel left, Fuel right)
    //{
    //    return left.Volume == right.Volume;
    //}

    //public static bool operator !=(Fuel left, Fuel right)
    //{
    //    return left.Volume != right.Volume;
    //}

    //// Need to override Equals and GetHashCode to get rid of warning.
    //public override bool Equals(object obj)
    //{
    //    if (obj == null || GetType() != obj.GetType())
    //    {
    //        return false;
    //    }

    //    return Volume.Equals(((Fuel)obj).Volume);
    //}

    //public override int GetHashCode()
    //{
    //    return Volume.GetHashCode();
    //}
}

Further technical details

EF Core version: 2.1.0
Database Provider: Microsoft.EntityFrameworkCore.Sqlite
Operating system: Win7
IDE: Visual Studio 2017 15.7.2

[ajcvickers]

Note for triage: I was able to repro this.

[smitpatel]

Structs cannot use operators == & != unless implemented https://stackoverflow.com/questions/15199026/comparing-two-structs-using

[ajcvickers]

This is approved for 2.1.3. Do not merge yet; branch is expected to open Monday.

Given these issues have been parked for some time, please be careful to ensure the correct commits get into the correct branches.

[ajcvickers]

@ajcvickers This issue is approved for patch and the release\2.1 branch is now open for merging. Please ensure:

• The appropriate changes get into both the release and dev branches
• Quirking is included for the release branch only

[theNETTechie]

Getting the same issue with .NET Core 3.0 and EF Core 3.0. Resolution is to implement operators == & != on the struct.

Stack trace:
System.AggregateException: One or more errors occurred. (Exception has been thrown by the target of an invocation.)
 ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.InvalidOperationException: The binary operator Equal is not defined for the types 'Entities.Inputs.Input1[System.Decimal]' and 'Entities.Inputs.Input1[System.Decimal]'.
   at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression right, Boolean liftToNull)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyAccessorsFactory.CreateCurrentValueGetter[TProperty](IPropertyBase propertyBase, Boolean useStoreGeneratedValues)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyAccessorsFactory.CreateGeneric[TProperty](IPropertyBase propertyBase)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyAccessorsFactory.Create(IPropertyBase propertyBase)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.<>c.<get_Accessors>b__39_0(PropertyBase p)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func2 valueFactory)    at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.get_Accessors()    at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBaseExtensions.GetPropertyAccessors(IPropertyBase propertyBase)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.GetCurrentValue[TProperty](IPropertyBase propertyBase)    at lambda_method(Closure , InternalEntityEntry )    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SidecarValues..ctor(InternalEntityEntry entry)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.EnsureTemporaryValues()    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetProperty(IPropertyBase propertyBase, Object value, Boolean isMaterialization, Boolean setModified, Boolean isCascadeDelete, CurrentValueType valueType)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetTemporaryValue(IProperty property, Object value, Boolean setModified)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.ValueGenerationManager.Generate(InternalEntityEntry entry)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean modifyProperties, Nullable1 forceStateWhenUnknownKey)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.PaintAction(EntityEntryGraphNode1 node)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode1 node, Func2 handleNode)    at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.AttachGraph(InternalEntityEntry rootEntry, EntityState targetState, EntityState storeGeneratedWithKeySetTargetState, Boolean forceStateWhenUnknownKey)    at Microsoft.EntityFrameworkCore.DbContext.SetEntityState(InternalEntityEntry entry, EntityState entityState)    at Microsoft.EntityFrameworkCore.DbContext.SetEntityState[TEntity](TEntity entity, EntityState entityState)    at Microsoft.EntityFrameworkCore.DbContext.Add[TEntity](TEntity entity)    at Microsoft.EntityFrameworkCore.Internal.InternalDbSet1.Add(TEntity entity)

[QuantumToasted]

It seems this issue still exists on MUCH newer versions. I'm running 5.0.0-preview.5.20278.2 and have just run into this issue.

System.InvalidOperationException: The binary operator Equal is not defined for the types 'Disqord.Snowflake' and 'Disqord.Snowflake'.
  at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression right, Boolean liftToNull)
  at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
  at Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.BuildPredicate(IReadOnlyList`1 keyProperties, ValueBuffer keyValues, ParameterExpression entityParameter)
  at Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.BuildLambda(IReadOnlyList`1 keyProperties, ValueBuffer keyValues)
  at Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.FindAsync(Object[] keyValues, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.FindAsync(Object[] keyValues)

It took a lot of googling but i eventually found this exact issue which seems to be related or maybe the same. Is the only current fix still to define == and !=? I can perhaps bother the developer of the library this struct is from to implement them, but I'd like to know if there is something else I could try. I did already try defining a ValueComparer<Snowflake> on models where it was appropriate, because I found another issue (don't have the link, sorry) that suggested it could solve the issue.

Is this worth re-opening or looking into again? Something seems up here, but it could just be my code.

[ajcvickers]

@QuantumToasted Please open a new issue and attach a small, runnable project or post a small, runnable code listing that reproduces what you are seeing so that we can investigate.