Using Exit to Terminate Repetition Statements To terminate
different types of repetition statements you can use a special
statement called: Exit statement. The program terminates that
repetition statement and continues execution with the first
statement after the repetition statement. Exit Do statement to exit
from Do While Loop, Do Loop While statement, Exit Select statement
to exit from a Select Case statement. Exit For statement to exit
from For Next and Created By Mayson Al-Duwais 2
Slide 3 10 Then Label1.Text &= Exit Do" Exit Do End If i +=
1 Loop While (i < 10) Dim i, result As Integer i = 1 result = 1
Do While (i < 10) result *= i Label1.Text &= ("i= " & i
& " result= " & result & vbCrLf) If result > 10 Then
Label1.Text &= Exit Do" Exit Do End If i += 1 Loop Created By
Mayson Al-Duwais3 When this condition is met, Exit Do statement is
executed causing loop to stop and the execution control goes to the
first statement after the loop">
Example Exit Do Do...Loop While Do While....Loop Dim i, result
As Integer i = 1 result = 1 Do result *= i Label1.Text &= ("i=
" & i & "result= " & result & vbCrLf) If result
> 10 Then Label1.Text &= Exit Do" Exit Do End If i += 1 Loop
While (i < 10) Dim i, result As Integer i = 1 result = 1 Do
While (i < 10) result *= i Label1.Text &= ("i= " & i
& " result= " & result & vbCrLf) If result > 10 Then
Label1.Text &= Exit Do" Exit Do End If i += 1 Loop Created By
Mayson Al-Duwais3 When this condition is met, Exit Do statement is
executed causing loop to stop and the execution control goes to the
first statement after the loop
Slide 4
Examples: Exit Select, Exit For Select...Case For...Next Dim
name As String = Ahmad Select name Case hind Label1.Text= Name is
& name Case Ahmad Label1.Text= Exit Select Exit Select Case
Asma Label1.Text= Name is & name Case Else Label1.Text= Not
Correct End Select For number1 As Integer =1 To 5 Label1.Text=
number1 = & number1 & vbCrLf If number1 Mod 3 = 0 Then
Label1.Text &= Exit For Exit For End If Next Created By Mayson
Al-Duwais4
Slide 5
Using Continue in Repetition Statements A Continue statement
terminates only the current iteration of a repetition statement and
continues execution with the next iteration of the loop. The
Continue Do statement can be used in a Do While Loop and Do Loop
While statement. The Continue For statement can be used in For Next
statement. Created By Mayson Al-Duwais 5
Slide 6
How Continue For work? When Continue For is encountered in a
For Next statement, execution continues with the statements
increment expression, then the program evaluates the loop-
continuation test. Created By Mayson Al-Duwais 6
Slide 7
Example Continue For For number1 As Integer = 1 To 5
Label1.Text &= "number1 =" & number1 & vbCrLf If
number1 Mod 3 = 0 Then Label1.Text &= "Continue For" &
vbCrLf Continue For End If Next Created By Mayson Al-Duwais7
Slide 8
How Continue Do Work? When Continue is used, the program
evaluates the loop- continuation (or loop-termination) test
immediately after the Continue statement executes. If a control
variables increment occurs in the loop body after the Continue
statement, the increment is skipped. Note that Continue Do is used
for both Do...Loop While and Do While...Loop Created By Mayson
Al-Duwais8
Slide 9
Example Continue Do When Increment is After Continue Do When
Increment is Before Continue Do Dim i, j As Integer i = 1 j = 1 Do
While (i < 6) j *= i Label1.Text &= ("i=" & i & ,j="
& j & vbCrLf) If j = 6 Then Label1.Text &= "Continue
Do" & vbCrLf Continue Do End If i += 1 increment After continue
Loop Dim i, j As Integer i = 1 j = 1 Do While (i < 6) j *= i
Label1.Text &= ("i=" & i & ,j=" & j & vbCrLf) i
+= 1 increment Before continue If j = 6 Then Label1.Text &=
"Continue Do" & vbCrLf Continue Do End If Loop Created By
Mayson Al-Duwais9
Slide 10
Using Continue in Repetition Statements Exit and Continue in
Nested Control Statements Exit For or Continue For can be used in a
Do While...Loop and Do...Loop While statements, as long as that
statement is nested in a For Next statement. Created By Mayson
Al-Duwais 10
Slide 11
Using Exit with Nested Repetition Statements of different types
Dim result As Integer = 1 For index As Integer = 1 To 3 Do While
result < 8 result += 1 Label1.Text &= "index = " & index
& " result = " & result & vbCrLf If result = 3 Then
Label1.Text &= "Continue While index = " & index & ",
result = " & result & vbCrLf Continue Do End If ' End If If
result = 5 Then Label1.Text &= "Exit While index = " &
index & ", result = " & result & vbCrLf Exit Do End If
' End If Loop ' End Do While...Loop Next ' End For...Loop Created
By Mayson Al-Duwais11
Slide 12
Using Exit with Nested Repetition Statements of different types
Created By Mayson Al-Duwais12
Slide 13
Using Continue in Repetition Statements Exit and Continue in
Nested Control Statements If there are nested loops of the same
type (for example, a For Next statement within a For Next
statement), the statement that immediately comes after the Exit or
Continue statement is the one affected. Created By Mayson
Al-Duwais13
Slide 14
Using Exit with Nested Repetition Statements of same types Dim
result, index As Integer result = index = 1 Do While index < 3
index += 1 Do While result < 8 result += 1 Label1.Text &=
"index = " & index & " result = " & result & vbCrLf
If result = 3 Then Label1.Text &= "Continue While index = "
& index & ", result = " & result & vbCrLf Continue
Do End If ' End If If result = 5 Then Label1.Text &= "Exit
While index = " & index & ", result = " & result &
vbCrLf Exit Do End If ' End If Loop ' End Do While...Loop Created
By Mayson Al-Duwais14
Slide 15
Using Exit with Nested Repetition Statements of same types
Created By Mayson Al-Duwais15
Slide 16
Created By Mayson Al-Duwais16
Slide 17
17 3.2 Strings Variables and Strings Using Text Boxes for Input
and Output String Properties and Methods: LengthToUpper TrimToLower
IndexOfSubstring
Slide 18
Strings (continued) Concatenation The Empty String Initial
Value of a String Widening and Narrowing Internal Documentation
Line Continuation Scope of a Variable 18
Slide 19
19 String Literal A string literal is a sequence of characters
surrounded by quotation marks. Examples: "hello" "123-45-6789" "#ab
cde?"
Slide 20
20 String Variable A string variable is a name to which a
string value can be assigned. Examples: country ssn word
firstName
Slide 21
String Variable (continued) Declaration: Dim firstName As
String 21 variable namedata type Assignment: firstName =
"Fred"
Slide 22
String Variable (continued) You can declare a string variable
and assign it a value at the same time. Dim firstName As String =
"Fred" 22
Slide 23
String Variable You can assign the value of one string variable
to another. Dim strVar1 As String = "Hello" Dim strVar2 As String =
"Goodbye" strVar2 = strVar1 lstOutput.Items.Add(strVar2) Output:
Hello 23
Slide 24
Variables and Strings Private Sub btnDisplay_Click(...) Handles
btnDisplay.Click Dim president As String president = "George
Washington" lstOutput.Items.Add("president")
lstOutput.Items.Add(president) End Sub Output: president George
Washington 24
Slide 25
Data Conversion Because the contents of a text box is always a
string, sometimes you must convert the input or output. dblVar =
CDbl(txtBox.Text) txtBox.Text = CStr(numVar) 25 converts a String
to a Double converts a number to a string
Slide 26
Concatenation Combining two strings to make a new string quote1
= "We'll always " quote2 = "have Paris." quote = quote1 &
quote2 txtOutput.Text = quote & " - Humphrey Bogart" Output:
We'll always have Paris. - Humphrey Bogart 26 Created By Mayson
Al-Duwais
Slide 27
Appending To append str to the string variable var var = var
& str Or as a shortcut var &= str 27 Created By Mayson
Al-Duwais
Slide 28
String Properties and Methods "Visual".Length is 6.
"Visual".ToUpper is VISUAL. "123 Hike".Length is 8. "123
Hike".ToLower is 123 hike. "a" & " bcd ".Trim & "efg" is
abcdefg. 28 Created By Mayson Al-Duwais
Slide 29
Positions in a String Positions of characters in a string are
numbered 0, 1, 2, . Consider the string Visual Basic. Position 0: V
Position 1: i Position 7: B Substring al begins at position 4 29
Created By Mayson Al-Duwais
Slide 30
Substring Method Let str be a string. str.Substring(m, n) is
the substring of length n, beginning at position m in str. Visual
Basic.Substring(2, 3) is sua Visual Basic.Substring(0, 1) is V 30
Created By Mayson Al-Duwais
Slide 31
IndexOf Method Let str1 and str2 be strings. str1.IndexOf(str2)
is the position of the first occurrence of str2 in str1. (Note: Has
value -1 if str2 is not a substring of str1.) "Visual
Basic".IndexOf("is") is 1. "Visual Basic".IndexOf("si") is 9.
"Visual Basic".IndexOf("ab") is -1. 31 Created By Mayson
Al-Duwais
Slide 32
The Empty String The string "", which has no characters, is
called the empty string or the zero-length string. The statement
lstBox.Items.Add("") skips a line in the list box. The contents of
a text box can be cleared with either the statement txtBox.Clear()
or the statement txtBox.Text = "" 32 Created By Mayson
Al-Duwais
Slide 33
Initial Value of a String Variable By default the initial value
is the keyword Nothing Strings can be given a different initial
value as follows: Dim name As String = "Fred" 33 Created By Mayson
Al-Duwais