"Unable to cast object of type 'System.Single' to type 'System.Double'." thrown when querying entity that contains property Double with some custom precision/scale values

[maumar]

Full repro:

    class Program
    {
        static void Main(string[] args)
        {
            using (var ctx = new MyContext())
            {
                ctx.Database.EnsureDeleted();
                ctx.Database.EnsureCreated();

                var e1 = new MyEntity { Double1 = 1123.432D };
                var e2 = new MyEntity { Double1 = 2123.432D };
                var e3 = new MyEntity { Double1 = 3123.432D };

                ctx.Entities.AddRange(e1, e2, e3);
                ctx.SaveChanges();
            }

            using (var ctx = new MyContext())
            {
                var result = ctx.Entities.ToList();
            }
        }
    }

    public class MyContext : DbContext
    {
        public DbSet<MyEntity> Entities { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<MyEntity>().Property(x => x.Double1).HasPrecision(17, 3);
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=SingleToDouble;Trusted_Connection=True;MultipleActiveResultSets=true;Column Encryption Setting=Enabled");
        }
    }

    public class MyEntity
    {
        public int Id { get; set; }
        public double Double1 { get; set; }
    }

Problem here is that even though property is typed as double, sql server stores it as real. In shaper we try to extract double from the reader the exception is thrown:

System.InvalidCastException: Unable to cast object of type 'System.Single' to type 'System.Double'.
   at Microsoft.Data.SqlClient.SqlBuffer.get_Double()
   at Microsoft.Data.SqlClient.SqlDataReader.GetDouble(Int32 i)
   at lambda_method(Closure , QueryContext , DbDataReader , ResultContext , SingleQueryResultCoordinator )
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.MoveNext() in D:\git\efcore\src\EFCore.Relational\Query\Internal\SingleQueryingEnumerable.cs:line 165
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

[BC89]

I came across this too and the only workaround I found was to make the datatype Float in SQL and then Double in my classes. Seems to be a variation on your issue.

[jgegenfurtner]

I solved the problem like this:

modelBuilder.Entity<MyEntity>().Property(x => x.Double1).HasColumnType("decimal").HasPrecision(17, 3);

This produces a migration which uses a decimal(17,3) type instead of a float for MS SQL Server 13.0.4001 with EF Core 5.0.4.

[HakanBayazitHabes]

This error usually occurs when the data record is saved as a float (System.Single in C#) in the model even though the data record is defined as a double (float in SQL Server).

• On the database side: float type is a double precision number.
• On the C# side: float is a single precision number.

This incompatibility occurs when an attempt is made to retrieve a double value from SQL Server, but this value is defined as a float in the model.

Like this:

For the solution on the C# side, you can convert the float value to double.

public double Barcode { get; set; }

I hope it is useful