What does the LINQ GroupBy method do?
Groups the elements of a sequence.
How do you group by elements in a LINQ query expression?
By using the group and the by keywords.
eg. group x by x.Field
What are the first two parameters that the GroupBy method takes (apart from the source)?
- Key Selector
2. Element Selector
What is the elementSelector parameter used for in a GroupBy method call?
Determining the return type of each element.
How do you define a new variable inside a LINQ query expression?
By using the let keyword.
eg. let x = new {y.Name};
What is the resultSelector parameter used for in a GroupBy method call?
Determining the data structure to be returned.
How do you use a result selector in a LINQ GroupBy query expression?
By using the into keyword after the group/by clause to define a variable that you use in a select clause to determine the return type.
What is the keySelector parameter used for in a GroupBy method call?
Determining what value to group the sequence by. This value also becomes the key of each group element.
What does the SelectMany extension method do?
It flattens a sequence by allowing us to work with nested sequences.
