Efcore.pg: Fixed-length char mapping is incompatible with CLR type-changing value converters

[andrewcfrancis2]

I tried using EnumToStringConverter to map an enum property on my entity class to a text database column as per:

https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions#built-in-converters

It works fine to read values out of the table but when I try to insert a new row, I get an exception when calling SaveChanges():

System.InvalidOperationException
  HResult=0x80131509
  Message=No coercion operator is defined between types 'EFCoreConsoleSample.LimitType' and 'System.String'.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.EntityFrameworkCore.Metadata.Internal.ClrAccessorFactory`1.Create(PropertyInfo propertyInfo, IPropertyBase propertyBase)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func`2 valueFactory)
   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.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at EFCoreConsoleSample.Program.Main(String[] args) in C:\git\EFCoreConsoleSample\EFCoreConsoleSample\Program.cs:line 15

The same thing works with SQL Server so it seems to be an issue with the PostgreSQL provider.

[YohDeadfall]

Could you provide the model configuration?

[andrewcfrancis2]

Here's a simple model that reproduces the issue:

```c#
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCoreConsoleSample
{
public class BloggingContext : DbContext
{
public DbSet Blogs { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.BlogTypeCode)
             .HasConversion(new EnumToStringConverter<BlogType>());
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseNpgsql("User ID=postgres;Host=localhost;Port=5432;Database=Repro;Pooling=true;");
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }

    [Column(TypeName = "char(3)")]
    public BlogType BlogTypeCode { get; set; }

}

public enum BlogType
{
    Per = 1,
    Com = 2,
}

}

The error occurs when I use the model like this:

```c#
using (var db = new BloggingContext())
{
    db.Blogs.Add(new Blog { Url = "http://www.google.com", BlogTypeCode = BlogType.Per });
    var count = db.SaveChanges(); // it throws an exception here
}

[austindrenski]

@andrewcfrancis2 Can you confirm your EF Core/npgsql versions?

[andrewcfrancis2]

@austindrenski I can reproduce the issue with the code above using EF Core and Npgsql v2.2.4:

[andrewcfrancis2]

Any news on this issue? Has someone been able to reproduce it? Is there any chance it will get fixed in the next release?

[cspwizard]

Have the same issue:

There is InvalidOperationException ('No coercion operator is defined between types 'EnumName' and 'System.String'.') when try to insert entity with enum property. This property is described via fluent api:

``` C#
modelBuilder.Entity().Property(e => e.EnumField).IsFixedLength().HasMaxLength(3)
.HasConversion(v => v.ToString(), v => Enum.Parse(v));

Almost same code (without `IsFixedLength()`) works fine
``` C#
modelBuilder.Entity<MyEntity>().Property(e => e.EnumField).IsFixedLength().HasMaxLength(3)
                .HasConversion<string>(v => v.ToString(), v => Enum.Parse<MyEnum>(v));

Steps to reproduce

Create entity with Enum field and describe it via fluent:

``` C#
modelBuilder.Entity().Property(e => e.EnumField).IsFixedLength().HasMaxLength(3)
.HasConversion(v => v.ToString(), v => Enum.Parse(v));

run migration (create db). And try to insert value in the table via EF Core.

### Further technical details

EF Core version: 3.0.0
Database provider: PostgreSQL (Npgsql.EntityFrameworkCore.PostgreSQL  Version=3.0.1)
Target framework: .NET Core 3.0
Operating system: windows 10


Stack trace:

at Microsoft.EntityFrameworkCore.Metadata.Internal.ClrAccessorFactory1.Create(MemberInfo memberInfo, IPropertyBase propertyBase) at Microsoft.EntityFrameworkCore.Metadata.Internal.ClrPropertyGetterFactory.Create(IPropertyBase property) at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.<>c.<get_Getter>b__33_0(PropertyBase p) at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func2 valueFactory)
at Microsoft.EntityFrameworkCore.Metadata.Internal.PropertyBase.get_Getter()
at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.ReadPropertyValue(IPropertyBase propertyBase)
at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.get_Item(IPropertyBase propertyBase)
at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.ChangeDetector.LocalDetectChanges(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 DBScaffold.Program.

d__0.MoveNext() in \DBScaffold\Program.cs:line 44

Code to reproduce:
``` C#
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using Microsoft.EntityFrameworkCore.ValueGeneration;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace EFCoreIssue
{
    public class MyEntity
    {
        public int Id { get; set; }

        public MyEnum EnumField { get; set; }
    }

    public enum MyEnum
    {
        One,
        Two
    }

    public class CurrentUserNameGenerator : ValueGenerator<string>
    {
        public override bool GeneratesTemporaryValues => false;

        public override string Next(EntityEntry entry) => "FooBarUser";
    }

    public class BloggingContext : DbContext
    {
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            //optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Test;ConnectRetryCount=0");
            optionsBuilder.UseNpgsql(@"Host=192.168.122.1;Database=pg_db;Username=postgres;Password=postgres");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder
                .Entity<MyEntity>()
                .Property(e => e.EnumField)
                .IsFixedLength()
                .HasMaxLength(3)
                .HasConversion(v => v.ToString(), v => Enum.Parse<MyEnum>(v));
        }
    }

    public static class Program
    {
        public static async Task Main()
        {
            using (var context = new BloggingContext())
            {
                context.Database.EnsureDeleted();
                context.Database.EnsureCreated();

                context.Add(new MyEntity { EnumField = MyEnum.Two });
                context.SaveChanges();
            }

            using (var context = new BloggingContext())
            {
                var value = context.Set<MyEntity>().FirstOrDefault();
            }
        }
    }
}

[cspwizard]

Hi Guys!

@YohDeadfall @austindrenski are there any plans on this issue?

Thanks!

[rockstardev]

Bump

[YohDeadfall]

@roji, could you take a look at it?

[roji]

Thanks for the reminder @YohDeadfall. This is a bug wherever a property is mapped to PostgreSQL fixed-length char (e.g. char(3)), and also uses a value converter to have a different CLR type in .NET.

[roji]

Note: as a workaround, map to varchar(3) instead of char(3) (or just to text) and everything should be fine.

[rockstardev]

Thanks for the fix and workaround @roji ... can confirm varchar worked for us; but am looking forward to switching to char.