Support .NET 10 span overloads

[StephenCleary]

When targeting .NET 10 (with C# 14), the compiler overload resolution rules changed (other docs), which breaks some usage of Contains and friends.

Example issue

Given the code:

string[] names = ["a", "b", "c"];
connection.Table<MyType>.Where(t => names.Contains(t.Name))

the Contains previously would resolve to Enumerable.Contains(names, t.Name), which was handled here. However, in .NET 10 (actually, C# 14), the Contains resolves to MemoryExtensions.Contains((ReadOnlySpan<MyType>)names, t.Name).

This results in SQL generated like select * from \"MyType\" where (\"Name\" in op_implicit((?,?))), which results in an exception like SQLite.SQLiteException: no such table: op_implicit.

EF Core had to change to support this, too

See similar issues for Expression tree handling in EFCore:

• First-class span support causes translation failure with Contains dotnet/efcore#35100 (fix)
• Also note this followup fix - in particular note that Contains behaves differently for arrays of enums, for some reason.

Recommended solution

Update TableQuery<T>.CompileExpr to:

• Detect MemoryExtensions.Contains (both the 2-argument and 3-argument versions if the 3rd argument is null), and treat it as though it were Enumerable.Contains, in particular unwrapping and ignoring the implicit cast.
• Consider whether to do the same for MemoryExtensions.SequenceEqual.

[SokoFromNZ]

Important addition: This also happens when targeting .NET9!

Any workaround suggestions until this is fixed?

[onionhammer]

Any workaround suggestions until this is fixed?

From Stephen's original code, you might try this

string[] names = ["a", "b", "c"];
connection.Table<MyType>.Where(t => names.ToList().Contains(t.Name))

[SokoFromNZ]

Any workaround suggestions until this is fixed?

From Stephen's original code, you might try this

string[] names = ["a", "b", "c"];
connection.Table.Where(t => names.ToList().Contains(t.Name))

Hmmm... but isn't this the code which has/shows the issue? At least as far as I understand his post.

[onionhammer]

@SokoFromNZ look a bit closer, I added a '.ToList()' in there

[StephenCleary]

The problem isn't actually .NET 10, but C# 14.

So another workaround is to specify <LangVersion>13</LangVersion> in your csproj (or Directory.Build.props).

[SokoFromNZ]

@onionhammer Sorry, I've missed that detail.
But adding it I get the error "table tolist not found".

Setting the language to C#13 like @StephenCleary suggested works

[StephenCleary]

adding it I get the error "table tolist not found".

I think it would work if the list wasn't in the LINQ expression. I.e., if string[] names = ["a", "b", "c"]; was List<string> names = ["a", "b", "c"]; - I haven't tried it myself, but I expect it to work. For now, at least (until List<T> supports an implicit conversion to ReadOnlySpan<T>, which it certainly could do but they haven't added yet).

[onionhammer]

Yeah, was hoping the SQL translator would figure it out, it does for Cosmos' query translator, I guess not for this repo. In this instance, you're better off using a list outside of the expression, as Stephen says

[SokoFromNZ]

Even with a List<string> names it does not work unfortunately. it gives the original error.

[dalux-shl]

We stumbled into this issue after upgrading to .NET 10 as well (C# 14). We found another workaround by explicitly defining the collection type as IEnumerable. This avoids the resolution to the new span overload of Contains:

IEnumerable<string> names = ["a", "b", "c"];
connection.Table<MyType>.Where(t => names.Contains(t.Name)) 

Are there any plans for a fix? It looks like EFCore has introduced a fix in dotnet/efcore#35100 and dotnet/efcore#37176.

[ericsink]

Darn. This issue keeps getting misplaced on my list. Thanks for the nag. I'll try to get to it soon.

[bbepis]

I have a fix for this issue at bbepis/FourLambda.SQLite@e0b5590