Problem with .Contains() on enum property with a custom ValueConverter

[Xayton]

Hello, while using Npgsql.EntityFrameworkCore.PostgreSQL version 5.0.0, I noticed a problem when using a custom ValueConverter on a property of type enum:

public class Blog
{
    public int Id { get; set; }
    public BlogType Type { get; set; } // This enum is converted using a custom ValueConverter.
}

public enum BlogType
{
    Public,    // Converted to "P".
    Internal   // Converted to "I".
}

// Converts the enum to a one-character string. This is just a simplified example.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    var converter = new ValueConverter<BlogType, string>(
       v => v == BlogType.Public ? "P" : "I",
       v => v == "P" ? BlogType.Public: BlogType.Internal);

    modelBuilder.Entity<Blog>().Property(e => e.Type).HasConversion(converter);
}

Given the configuration above, the problem happens when querying the blogs with .Contains() on the Type property:

var requiredTypes = new[] {BlogType.Public, BlogType.Internal}; // Must be an array to repeat the problem.
var blogs = _context.Blogs.Where(b => requiredTypes.Contains(b.Type)).ToArray();

Generated SQL query:

Executed DbCommand (11ms) [Parameters=[@__requiredTypes_0='System.String[]' (DbType = Object)], CommandType='Text']
SELECT b.id, b.type
FROM blogs AS b
WHERE b.type = ANY (@__requiredTypes_0)

Here the contents of the @__requiredTypes_0 parameter are not visible (see #1779), but the array contains the string representation of the enum values, instead of the one-character strings provided by the ValueConverter.
So the parameter contains {Public, Internal} instead of {P,I} and consequently no blog results are returned.

May be related to: #1559.

Thank you.

[roji]

@Xayton thanks for reporting this - I've verified this as a bug and fixed it in #1797. Unfortunately this let into a rabbit hole with two other issues, and the whole thing is a bit much for backporting to a 5.0 patch release...