Is it possible to call a scalar function in entity framework?

Question

I have a scalar function that takes 2 parameters and returns an integer.

In sql I can call the function by simply including it in my sql statement. IE

select funcname(dateparamfrom, 
dateparamto) as numholidays from table

My question is as part of a linq entity framework 8 join query how to I include that scalar function call in my query.

I have 2 model classes for 2 tables and I am able to join those but the query in question uses a scalar function to return a number based on how the function is written, EF 8.

Var data from context.dbtbale name

I know you can use the context.sqlquery method but is this the correct way?

Thanks

Answer 1

You can map your own functions using EF Core. To do this you need to configure your DbContext, for example:

public class MyContext : DbContext
{
    // This is a stub method used only by EF
    public int GetDayCount(DateTime from, DateTime to)
        => throw new InvalidOperationException();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Now map the stub method into a call in the database
        modelBuilder
            .HasDbFunction(
                typeof(MyContext).GetMethod(nameof(GetDayCount),
                    new[] { typeof(DateTime), typeof(DateTime) })!)
            .HasName("NameOfFunctionInDatabase");

        base.OnModelCreating(modelBuilder);
    }


    public DbSet<Meeting> Meetings { get; set; }
}

Now you can use the function like this:

var result = context.Users
    .Where(m => context.GetDayCount(m.From, m.To) > 5)
    .ToList();

See the docs for more detail