Handy Linq Queries

Handy Linq Queries Tips

Tip: Count Parent & Child Records at once

Solution: 

parent.Where(i => i.childId == 5).SelectMany(e => e.child).Count();

Tip: Selection of Multiple Fields from List or Database, and short it over a field or multiple fields. (note the last statement of the order by taking precedence over previous)

Solution: 

var cat = db.categories
    .Select(cat => new { cat.Category, cat.Id })
    .OrderBy(o => o.Id)
    .OrderByDescending(o => o.Category);

  //.ThenByDescending(o => o.Category);

output

9        Utilities

3        Transportation

10       Shelter

2        Restaurants

11       Personal

15       Office exp

17       Miscellaneous

5        Medical

12       Kids schooling

6        Insurance

13       Household items

1        Grocery

4        Gifts

14       Fun money

8        Education

16       Donation

7        Clothing

Tip: Change all value for a list of items at once (without loop) 

Solution:

_extendedExpenses.ToList().ForEach(e => e.IsChecked = isChecked);

Tip: GroupBy on Multiple Columns/Fields

Solution:

foreach (var stDepart in strataDepartments.GroupBy( x=> new  { x.Name, x.Code }))
{
    System.Diagnostics.Debug.WriteLine($"Name:{stDepart.Key.Name} Code:{stDepart.Key.Code}" +
        $" Count: {stDepart.Count()}");
}