Some values in queries are not going through value converter

[cincuranet]

With the setup below the query db.Set<FooBar>().Where(x => x.FooBarBaz.Contains("test")).Load() is translated to:

SELECT [x].[Id], [x].[FooBarBaz]
FROM [FooBar] AS [x]
WHERE CHARINDEX(N'test', [x].[FooBarBaz]) > 0

The test didn't went through the converter. Similarly db.Set<FooBar>().Where(x => x.FooBarBaz.StartsWith("test")).Load() and db.Set<FooBar>().Where(x => x.FooBarBaz.EndsWith("test")).Load() respectively result in following SQL where the LEN is not not transformed:

SELECT [x].[Id], [x].[FooBarBaz]
FROM [FooBar] AS [x]
WHERE [x].[FooBarBaz] LIKE N'ToStoreExpr' + N'ToStoreExpr' AND (LEFT([x].[FooBarBaz], LEN(N'test')) = N'ToStoreExpr')

SELECT [x].[Id], [x].[FooBarBaz]
FROM [FooBar] AS [x]
WHERE RIGHT([x].[FooBarBaz], LEN(N'test')) = N'ToStoreExpr'

Setup

class FooBar
{
	public int Id { get; set; }
	public string FooBarBaz { get; set; }
}

class MyContext : DbContext
{
	protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
	{
		base.OnConfiguring(optionsBuilder);

		optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Integrated Security=true;database=test");
	}

	protected override void OnModelCreating(ModelBuilder modelBuilder)
	{
		base.OnModelCreating(modelBuilder);

		modelBuilder.Entity<FooBar>()
			.Property(x => x.FooBarBaz)
			.HasConversion(new DummyConverter());
	}
}

class DummyConverter : ValueConverter<string, string>
{
	public DummyConverter(ConverterMappingHints mappingHints = default)
		: base(ToStoreExpr, FromStoreExpr, mappingHints)
	{ }

	static Expression<Func<string, string>> FromStoreExpr = _ => nameof(FromStoreExpr);
	static Expression<Func<string, string>> ToStoreExpr = _ => nameof(ToStoreExpr);
}

Further technical details

EF Core version: 2.1.0-preview1-final
Database Provider: Microsoft.EntityFrameworkCore.SqlServer

[ajcvickers]

This is a known issue with converters which is due to:

• Lack of inference of the store type and facets in some translations, such as the Contains function translation--tracked by Query: Allow store types and type facets to be set explicitly (EF.StoreType) #4978
• Lack of support in the query pipeline for performing different SQL translations when converters are being used--tracked by Support (custom) member/method translations on value-converted types #10434

We plan to add a warning in 2.1.