Calculating user efficiency on a time period with Linq

Question

I have this expression:

    public static readonly Expression<Func<ApplicationUser, decimal>> EfficiencyPercentExpr = e =>
        (e.ExecutorOrders.Where(x => x.Added >= DbFunctions.AddDays(SqlFunctions.GetUtcDate(), -30)).Count(x => x.Status != Order.OrderStatus.Deleted) > 0)
        ?
        (
        e.ExecutorOrders.Where(x => x.Added >= DbFunctions.AddDays(SqlFunctions.GetUtcDate(), -30)).Count(x => x.Status != Order.OrderStatus.Deleted)
        /
        e.ExecutorOrders.Where(x => x.Added >= DbFunctions.AddDays(SqlFunctions.GetUtcDate(), -30)).Count()
        )
        :
        0
    ;

This expression calculates the user's efficiency by calculating the percentage of successful orders from a total of the last 30 days.

How can I make it more clear?

Update:

There is a second approach of writing the expression, but it generates more expensive SQL query.

    private static readonly Expression<Func<ApplicationUser, decimal>> efficiencyPercentExpr = e =>
        e.ExecutorOrders.Where(x => !x.IsNotConsidered && x.Added >= DbFunctions.AddDays(SqlFunctions.GetUtcDate(), -30))
        .GroupBy(x => 1, (k, g) => new { Count = g.Count(), CountUndeleted = g.Count(x => x.Status != Order.OrderStatus.Deleted) })
        .Select(x => x.CountUndeleted > 0 ? (decimal)x.CountUndeleted / (decimal)x.Count : 0).FirstOrDefault();

Answer 1

1. Don't one line things that shouldn't be one lined. Just because you can do something, doesn't mean that you should.
2. Extract the duplicated query into a method of it's own that returns an IQueryable

3. Don't query the database twice for the same count, execute the query and store it in a variable.

   private IQueryable<foo> ExecutorOrdersInLast30Days(ApplicationUser e)
   {
       return e.ExecutorOrders.Where(x => x.Added >= DbFunctions.AddDays(SqlFunctions.GetUtcDate(), -30));
   }
   
   private decimal EfficiencyPercent(ApplicationUser e)
   {
       var nonDeletedOrders = ExecutorOrdersInLast30Days(e).Count(x => x.Status != Order.OrderStatus.Deleted);
       if ( nonDeletedOrders > 0)
       {
           return nonDeletedOrders / ExecutorOrdersInLast30Days(e).Count();
       }
       else
       {
           return 0;
       }
   }