Chapter 8 ArraysSingle-Dimension ArraysSubscriptsDeclaration Statement for Arraysforeach Statementforeach ExamplesStructuresStructures cont – Simply declaring a datatypeStructures cont.Table LookupUsing List Boxes with ArraysMultidimensional ArraysMultidimensional Arrays cont.Initialize Two-Dimensional ArraysPrinting a Two-Dimensional TableSumming a Two-Dimensional TableLookup Operation for Two-Dimensional TablesPowerPoint PresentationChapter 8 ArraysProgramming in C# .NET © 2003 by The McGraw-Hill Companies, Inc. All rights reserved.2Single-Dimension ArraysAn array is a list or series of values, similar to a list box without the boxCreate an array to keep a series of variables for later processingEach individual variable in an array is referenced by the same nameArrays also called tables or subscripted variablesEach individual variable is an element of the arraySubscript (or index) inside parentheses is the position of the element within the array3SubscriptsSubscripts may be constants, variables, or numeric expressionsSubscripts must be integersSpecify the number of elements in the array in the array’s declaration statementArray subscripts are zero basedYou declare a data type for the array and all array elements must be the same data typeA subscript must reference a valid element of the arrayException will be thrown if a subscript is out of range4Declaration Statement for ArraysGeneral Forma) Datatype[] ArrayName = new DataType[NumberofElements];b) Datatype[] ArrayName = new DataType[] {InitialValueList};c) Datatype[] ArrayName = {InitialValueList};Examplesa) string[] strName = new string[25]; <- initialized to emptya) decimal[] decBalance = new decimal[10]; <- initialized to zeroa) string[] strProduct = new string[99];b) int[] intValue = new int[] {1,5,12,18,20};c) string[] strName = {“Sean”, “Sam”, “Sally”, “Sara”};5foreach Statementforeach is a looping construct that does not require manipulation of the array subscriptsGeneral Formforeach (DataType ElementName in ArrayName){//Statement(s) in loop}C# automatically references each array element, assigns its value to ElementName, and makes one pass through the loopThe foreach loop will execute if the array has at least one element6foreach Examplesforeach (string strOneName in strName){Console.WriteLine(strOneName); //Write one element of the array}int intSum;foreach (int intOneTotal in intTotal){intSum += intOneTotal; //Add each element of the array to intSum}7StructuresCombine multiple fields of related data to create a new structure (record)Defining a structure is similar to defining a new data typeStruct declaration cannot go inside a methodBy default, a structure is publicIf an array is included inside a structure, you cannot specify the number of elements8Structures cont – Simply declaring a datatypeGeneral Form[public | private] struct NameOfStruct{public Datatype FirstField;public Datatype SecondField;. . .}Examplepublic struct Product{public string strDescription;public string strID;public int intQuantity;public decimal decPrice;}9Structures cont.Once a structure is created, declare variables of the structure typeEach field of data in variable declared as a structure is called an element of the structureC# does not allow declaration of the number of elements in an array in the struct declarationUsing a value as an index to an array is called a direct referenceView contents of array elements in break time using the Autos window by clicking on the plus sign at left of the array name10Table LookupDetermine which array element to update or access using a table lookupUse a while loop for a table lookupValidate input before performing table lookupCompare input to each element in array to find a matchIt is not necessary to arrange fields being searched in any particular sequence11Using List Boxes with ArraysIt is a good idea to use a list box for input of information to lookup in arrayUse the SelectedIndex property to determine the array subscriptSelectedIndex holds the position or index of the selected item from the list12Multidimensional ArraysTwo-dimensional arrays have rows and columnsArray declaration specifies number of rows and columns in the arrayRow is horizontal and column is verticalMust always use two subscripts to refer to individual elements of tableRow is first subscriptColumn is second subscript13Multidimensional Arrays cont.General FormDataType[,] ArrayName = new Datatype[NumberOfElements,NumberOfElements];DataType[,] ArrayName = new DataType[ , ] = {ListOfValues};Cannot specify the number of elements within parentheses and specify the initial valuesMust use a comma to specify two dimensions to the arrayExamples:string[,] strName = new string[3,4]; <- 3 rows , 4 columnsstring[,] strName = new string[ , ] = {{“James”, “Mary”, “Sammie”, “Sean”}, <- row 0{“Tom”, “Lee”, “Leon”, “Larry”}, <- row 1 {“Maria”, “Margaret”, “Jill”, “John”}}; <- row 214Initialize Two-Dimensional ArraysNumeric array elements are initialized to 0 and strings are initialized to empty stringsUse nested for loops to initialize array elementsint intRow, intColumn;for (intRow = 0; intRow < 3; intRow++){for (intColumn = 0; intColumn < 4; intColumn++){strName[intRow, intColumn] = “”;}}15Printing a Two-Dimensional TableUse a foreach loop to print contents of a two-dimensional tableProcesses all the columns in a row thenmoves to the next rowUse a for loop and specify a new x coordinate for each element to print on the same line16Summing a Two-Dimensional TableThere are several ways to sum a tableSum the columnsSum the rowsSum the figures in both directions and double-check the totalsTo sum an array in both directions, create two one-dimensional arrays to store the total fields17Lookup Operation for Two-Dimensional TablesUse direct reference and table lookup as in single-dimensional arraysLimitationsRow and column subscripts must be available to use direct reference Table lookup is the most common lookup techniqueLookup processes may require additional one-dimensional arrays or listsUse list boxes or text