How to use lambda expression when defining index filter or check constraint in Entity Framework Core?

Question

Let's say I have an entity that looks something like this

public class ApplicationConfiguration
{
    public int Id { get; set; }
    public ApplicationId { get; set; }
    public string Name { get; set; }
    public DeploymentStateType State { get; set; }
}

public enum DeploymentStateType
{
    Unknown,
    InDeployment,
    DeploymentComplete
}

In my model builder, I want to define a filtered index on ApplicationId where State == InDeployment.

Seemingly, the fluent API only allows a hardcoded SQL fragment via this syntax:

modelBuilder.Entity<ApplicationConfiguration>()
    .HasIndex(ac => ac.ApplicationId)
    .HasFilter("State == 1");

Now this is obviously fragile for two reasons:

• No intellisense/refactoring support for the column name ("State") in the filter expression
• Reference to enum "magic number"

The way I'm solving the problem is:

modelBuilder.Entity<ApplicationConfiguration>()
    .HasIndex(ac => ac.ApplicationId)
    .HasFilter($"{nameof(ApplicationConfiguration.State)} == {(int)DeploymentStateType.InDeployment}");

But this is obviously ugly and unwieldy.

In an ideal world, I would be able to do specify it using a lambda:

modelBuilder.Entity<ApplicationConfiguration>()
    .HasIndex(ac => ac.ApplicationId)
    .HasFilter(ac => ac.State == DeploymentStateType.InDeployment);

However, HasFilter() does not seem to have an overload that accepts a lambda. (As of writing, I'm using EF Core 6.0.5 which seems to be the latest stable release.)

This should theoretically be possible, because:

• Where() knows how to do it
• model builder knows it's building a model from SQL Server dialect, so already at this stage know how to generate correct SQL

This problem pertains to HasCheckConstraint() as well, which also only seems to accept a raw SQL string.

Q: Is there a way to have EF generate the SQL fragment for me, having the filter lambda as an input?