1. CSCI 3328 Object Oriented Programming in C# Chapter 8: LINQ and Generic Collections – Exercises 1 Xiang Lian The University of Texas – Pan American Edinburg, TX 78539 lianx@utpa.edu

2. Objectives In this chapter, you will do some exercises related to: –LINQ –Collections 2

3. Multiple Choices Use the _______ property of the Array class to find the number of elements in the List. –A. GetLength B. GetLength() C. Length D. Length() An array’s length is ______. –A. one more than the array’s last index B. one less than the array’s last index C. the same as the array’s last index D. returned by size() – 1 The process of ordering the elements of an array is called ____ the array. –A. allocating B. sorting C. declaring D. initializing The LINQ ________clause is used for filtering. –A. orderby B. from … in C. where D. select _______are classes specifically designed to store groups of objects and provide methods that organize, store and retrieve those objects. –A. Int B. Classes C. Collections D. Objects 3

4. Multiple Choices (cont'd) To add an element to the end of a List, use the _____ method. –A. insert B. Items C. add D. Item To get only unique results from a LINQ query, use the ______ method. –A. Unique B. Only C. Distinct D. Solely To sort the elements of an LINQ query, use ___ clause. –A. orderby B. ascending C. where D. select Which extension method can determine the number of elements in the result of an LINQ query? –A. Sum B. Distinct C. Length D. Count 4

5. True/False Statements The where clause in an LINQ query is optional The orderby clause of an LINQ query by default sorts the array in descending order LINQ can query arrays of only primitive types LINQ queries can be used on both arrays and collections The Remove method of the List class removes an element at a specific index 5

6. True/False Statements (cont'd) To declare an integer array of two rows and five columns, the expression should be: –int[] a = new int [3, 6]; To sort an integer array, myArray, in decreasing order, we can use the following LINQ query: –var sorted = from e in myArray order by e descending select e To add an integer to a List variable, listScores, we can use: –listScores.Items.Add(); 6

7. Write a Program Assume a class Invoice includes 4 properties: –PartNumber (int) –PartDescription (string) –Quantity of the item being purchased (int) –Price (decimal) Write a program that performs queries over the array, Invoices, of Invoice objects: –1. Use LINQ to sort the Invoice objects by PartDescription; –2. Use LINQ to sort the Invoice objects by Price; –3. Use LINQ to select the PartDescription and Quantity, and sort the results by Quantity; –4. Use LINQ to select from each Invoice the PartDescription and the value of Invoice (i.e., Quantity*Price); –5. Use the results of the LINQ query in Part 4, select the InvoiceTotal in the range $200 to $500. 7

8. Write a Program (cont'd) Write a console application program that inserts 30 random letters into a List. Perform the following queries on the List and display your results: –1. Use LINQ to sort the List in ascending order –2. Use LINQ to sort the List in descending order –3. Display the List in ascending order with duplicates removed 8

9. Write a Program (cont'd) Declare an array, numArray, to hold 100 integer numbers Assign random numbers within [1, 100] into this array Use the LINQ query to sort this array Use the LINQ query to check whether a number 50 exists in this array 9

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