LINQ

Question 1

What is a list?

Answer 1

A list is similar to an array but provides additional functionality, such as dynamic resizing.

Question 2

What is LINQ?

Answer 2

C#’s LINQ(Language-Integrated Query) capabilities allow you to write query expressions that retrieve information from a variety of data sources, not just databases.

LINQ to Objects can be used to filter arrays and Lists, selecting elements that satisfy a set of conditions.

Question 3

What is a LINQ provider?

Answer 3

A LINQ provider is a set of classes that implement LINQ operations and enable programs to interact with data sources to perform tasks such as projecting, sorting, grouping and filtering elements.

Question 4

What are the two LINQ approaches?

Answer 4

One uses an SQL-like syntax, and the other uses method-call syntax.

Question 5

What would filtering an array of integers with LINQ look like?

Answer 5

Question 6

How does a LINQ query begin?

Answer 6

A LINQ query begins with a from clause, which specifies a range variable (value) and the data source to query (values).

Question 7

What is the range variable?

Answer 7

The range variable represents each item in the data source, much like the control variable in a foreach statement.

Question 8

What depicts which elements are selected?

Answer 8

If the condition in the where clause evaluates to true, the element is selected.

A predicate is an expression that takes an element of a collection and returns true or false by testing a condition on that element.

Question 9

What determines what value appears in the results?

Answer 9

The select clause determines what value appears in the results.

Question 10

How do you sort the query results?

Answer 10

The orderby clause sorts the query results in whatever order you choose.

Question 11

What is the Interface IEnumerable?

Answer 11

Question 12

How would you use LINQ to filter through an array of employee objects?

Answer 12

Question 13

What will LINQs Any method return?

Answer 13

Returns true if there is at least one element and false if there are no elements.

Question 14

What will LINQs First method return?

Answer 14

The first methos returns the first element in the result.

Question 15

What will LINQs Count method return?

Answer 15

The count method of the query result returns the number of elements in the results.

Question 16

What will LINQs Select clause do?

Answer 16

The select clause can be userd to select a member of the range variable rather than the range variable itself.

Question 17

What will LINQs Distinct method return?

Answer 17

The distinct method removes duplicate elements, causing all elements in the result to be unique.

Question 19

How would you use LINQ to query a list collection?

Answer 19

The same as an array.

Question 20

What does the let clause do?

Answer 20

It can be used to create a new range variable to store a temporary result for use later in the LINQ query

Question 21

When do LINQ querys execute?

Answer 21

LINQ uses deferrec execution - the query eexecutes only when you access the results, not when you define the query.