LINQ 201 – Changing the way I work with lists
LINQ brings the set-based power of SQL-like syntax to VB.NET and C#. I thought I’d highlight some of the ways this has changed and simplified my code.
Find an element in a list
Pre-LINQ:
function FindItem(key as string) For each item in myList if item.Key = key then return item Next end function dim foundItem = FindItem(key) if foundItem isnot nothing then ...process item else ...not found end if
Post-LINQ:
dim foundItems = from item in MyList where item.Key = key if foundItems.Any then ...process item (foundItems.First) else ...not found end if
Find matching elements in a list
Pre-LINQ:
dim newList = new List(Of SomeClass) for each item in oldList if item.SomeField = "Foo" then newList.Add(item) next
Post-LINQ:
dim newList = from item in oldList where item.SomeField = "Foo"
Convert a list of items of one type into another
Pre-LINQ:
dim newList = new List(Of NewType) for each item in oldList dim newItem = new NewType newItem.Field1 = item.FieldA newItem.Field2 = item.FieldB newList.Add(newItem) next
Post-LINQ:
dim newList = from item in oldList _ select new NewType with _ {.Field1 = item.FieldA, _ .Field2 = item.FieldB}
Sorting a list
Pre-LINQ:
Way too hard. Suffice to say it involved creating a new IComparer class or implementing IComparable in the existing class
Post-LINQ:
dim sortedList = from item in myList _ order by item.Field1
(or you could use lambda expression, but I find the above more readable)
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