using System;

using System.Linq;

using Microsoft.EntityFrameworkCore;

using Microsoft.EntityFrameworkCore.Storage;

using Microsoft.EntityFrameworkCore.SqlServer;

using Microsoft.EntityFrameworkCore.Query.SqlExpressions;

using Microsoft.EntityFrameworkCore.Metadata.Builders;

using Microsoft.EntityFrameworkCore.Infrastructure;

using System.ComponentModel.DataAnnotations.Schema;

public class Program

{

    public static void Main()

    {

        using var ctx = new MyContext();

        var baseQuery = ctx.Tests;

        var results = baseQuery.Where(t => MyContext.TryConvertInt(t.Value) == 1);

        Console.WriteLine(results.ToQueryString());

    }

}

​

public class MyContext : DbContext

{

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

    {

        optionsBuilder.UseSqlServer("Data Source=.");

    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)

    {

        modelBuilder.HasDbFunction(

            this.GetType().GetMethod(nameof(TryConvertInt)),

            f => f

                .IsBuiltIn()

                .HasParameter("value", p => p.HasStoreType("sql_variant"))

                .HasName("TRY_CONVERT").HasTranslation(args =>

                new SqlFunctionExpression(

                    "TRY_CONVERT", 

                    [

                        new SqlFragmentExpression("int"),

                        args.First()

                    ],

                    true,

                    [false, true],

                    typeof(int),

                    null

                )

            )

        );

    }

    public DbSet<TestEntity> Tests {get;set;} = null!;

    public static int TryConvertInt(object value) => throw new NotImplementedException();

}

​

public class TestEntity

{

    public int Id {get;set;}

    [Column(TypeName = "sql_variant")]

    public object Value {get;set;}

}