Hot-Link Menu in Right-Side Column

Last Updated 6-30-2010

Visual Basic Arrays Page 3

The form at Design Time should look similar to the diagram below:

Figure Array-7: Form at Design Time

Add Ons Desktops Net Books Laptops PDA Mac Gaming Products Nintendo Gaming Products PC Gaming Products Play Station 3 Games Sony PSP Gaming Products Wii Gaming Products Xbox Gaming Products Accessories Blue Tooth Car Electronics Cell Phones & Service GPS Devices Home Theater Marine Electronics Mobile Broadband Office Products Photography Products Precision Measurement Security Products Video Products Business Software Graphics Software Mac Software Multimedia Networking Software Operating Systems Programming Software Security Software Utilities Web Development Apple Computer Books Certification Books Business Books Database Books Computer Hardware Computer Networking Computer Programming Computer Science Computer Security Digital Music Digital Photography Game Strategy Books General Computer Graphics Design Microsoft Computing Mobile Wireless Operating Systems Science Books Technical Books Web Development

The form at design time with the controls expanded is shown below:

Figure Array-8: Form at Design Time (expanded)

Enter the code as shown below:

Public Class Form1

'Declare Array Visible to Entire Class

Private NumberOfScores As Integer = 0
Private MaxEntries As Integer = 20
Private ScoreArray(MaxEntries ) As Double 


'Enter scores - press <Enter> to place value into Array

Private sub   txtQuizScore_Enter (ByVal sender As System .Object , _
        ByVal e As KeyPressEventArgs ) Handles txtQuizScore.KeyPress

    
    Dim EnteredValue As Double 
    Dim DataString As String 

    If e.KeyChar = ControlChars.Cr  Then
    
        If Double .TryParse (txtQuizScore .Text ,EnteredValue  ) = False then
            MessageBox .Show (" You must enter a numeric value like 1 or 2")
            txtQuizScore .Clear 
            txtQuizScore .Focus 
            Exit Sub 
        End If

        If EnteredValue  < 0 or EnteredValue  >10 then
            MessageBox .Show ("Valid range is between 0 and 10, 7 would work " _
                & EnteredValue .ToString  & " Does not")
            txtQuizScore .Clear 
            txtQuizScore .Focus
            Exit Sub  
        End If

        If NumberOfScores < MaxEntries then
            ScoreArray (NumberOfScores) = EnteredValue 
            NumberOfScores += 1
            DataString = NumberOfScores .ToString + ".  " + EnteredValue .ToString 
            lstDisplay.Items.Add (DataString )
        End If

        txtQuizScore.Clear 
        txtQuizScore .Focus 


    End If 

End Sub 


'Clear Last Entry

Private Sub btnClearLast_Click( ByVal sender As System.Object, _
	 ByVal e As System.EventArgs) Handles btnClearLast.Click
    NumberOfScores -= 1
    lstDisplay .Items .RemoveAt (NumberOfScores )
    txtQuizScore .Clear 
    txtQuizScore .Focus 
    
End Sub


'Clear All Entries

Private Sub btnClearAll_Click( ByVal sender As System.Object, _
	ByVal e As System.EventArgs) Handles btnClearAll.Click
    lstDisplay .Items .Clear 
    NumberOfScores = 0
    txtQuizScore .Clear 
    txtQuizScore.Focus 
End Sub


'Calculate Min, Max and Average

Private Sub btnStatistics_Click( ByVal sender As System.Object, _
	ByVal e As System.EventArgs) Handles btnStatistics.Click
    Dim Output As String 
    Dim Average As Double = 0
    Dim Sum As Double = 0
    Dim ScoreNumber As Integer 
    Dim MinScore As Double = ScoreArray (0)
    Dim MaxScore As Double = ScoreArray (0)

    lstDisplay .Items .Add ("")

    For ScoreNumber =0 to NumberOfScores - 1
        Sum+=ScoreArray (ScoreNumber)
        If(MinScore >ScoreArray (ScoreNumber) ) then
            MinScore = ScoreArray (ScoreNumber)
        End If
        If(MaxScore < ScoreArray (ScoreNumber)) then
            MaxScore = ScoreArray (ScoreNumber)
        End If
    Next


    If(NumberOfScores>0 ) then
        Average = Sum/NumberOfScores
    End If
    

    Output ="Average: " + Average .ToString 
    lstDisplay .Items .Add (Output )
    Output ="Minimum: " + MinScore .ToString 
    lstDisplay .Items .Add (Output )
    Output ="Maximum: " + MaxScore .ToString 
    lstDisplay .Items .Add (Output )
    
    
End Sub

End Class


						

The form at design time with the controls expanded is shown below:

Let's take a look at the code in action:

• Private NumberOfScores As Integer = 0: This tells us the size of the array. It is accessible in the entire class.
• Private MaxEntries As Integer = 20: Maximum number of entries allowed in this example.
• Private ScoreArray(MaxEntries ) As Double: The Array of Quiz scores is also accessible to all functions on this form.
• Private sub txtQuizScore_Enter (ByVal sender As System.Object , ByVal e As KeyPressEventArgs)
      Handles txtQuizScore.KeyPress
• Private sub txtQuizScore_Enter: This function will be called when the <Enter> key is pressed in the TextBox.
• ByVal sender as System.Object: A reference to the TextBox control.
• ByVal e As KeyPressEventArgs: e is every key pressed. KeyPressEventArgs decodes which key is pressed.
• Handles txtQuizScore.KeyPress: Call this subroutine after every key press in the TextBox.


• Dim EnteredValue As Double: This will be the numeric variable which receives the number entered in the textbox.
• Dim DataString as String: A String used to build a reflection of the data entered to be displayed in the ListBox.


• If e.KeyChar = ControlChars.Cr Then: Test for <Enter> key.
• e.KeyChar: The last key pressed in the TextBox.
• e: is the key pressed on the keyboard.
• KeyChar: is used as the reference in the KeyPressEventArgs class descriptor.
• ControlChars.Cr The comparison value for the <Enter> key when using KeyPressEventArgs.
• ControlChars: is used to decode KeyChar.
• Cr: is the value associated with the <Enter> key.


• If Double .TryParse (txtQuizScore .Text ,EnteredValue ) = False then: Check for Numeric Value.
• Double.TryParseSearch the text for a value of type double.
• txtQuizScore.Text: The text is the Quiz Score TextBox is what will be scanned for a numeric value.
• EnteredValue: The recipient of the Double value if the scan is successful.
• =False then: Text was in improper format - execute code on next line.
• MessageBox .Show (" You must enter a numeric value like 1 or 2"): Display a message box with some smart aleck comment for those that refuse to follow directions.
• txtQuizScore .Clear: Remove the information that was previously in the TextBox.
• txtQuizScore.Focus: Place the Cursor in the empty TextBox, so they start right in entering data.
• Exit Sub: Error in Data Entry, no point in going any further.
• End If: End of Data Entry check for non-numeric value.



Help Support this site - Click this ad



• If EnteredValue < 0 or EnteredValue >10 then: Check for valid range between 0 and 10.
• If NumberOfScores < MaxEntries then: Make sure they aren't getting too ambitious, and going out of bounds on the array.
• ScoreArray (NumberOfScores) = EnteredValue: All is good, place value in next array location.
• NumberOfScores += 1: Move to the next Array location.
• DataString = NumberOfScores .ToString + ". " + EnteredValue .ToString: Create string echoing number entered.
• lstDisplay.Items.Add (DataString ): Visual Basic syntax to place data at the end of the ListBox display.



• Private Sub btnClearLast_Click( ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClearLast.Click.
• Visual Basic generated code to respond to the Clear Last Entry button being pressed.


• NumberOfScores -= 1: Reset Array index to last entry entered.
• lstDisplay .Items .RemoveAt (NumberOfScores ): Remove the Last Entry.
• txtQuizScore.Clear: Clear the data entry TextBox.
• txtQuizScore.Focus: Set the cursor in the data entry TextBox.
• Private Sub btnClearAll_Click( ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClearAll.Click.
• Visual Basic Generated code to respond to the Clear All button being pressed.


• lstDisplay .Items .Clear: Syntax to clear a ListBox.
• NumberOfScores=0: Effectively clear the array by resetting the index to 0.
• txtQuizScore.Clear: Clear the data entry TextBox.
• txtQuizScore.Focus: Set the cursor in the data entry TextBox.



• Private Sub btnStatistics_Click( ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStatistics.Click.
• Visual Basic generated code to respond to the Statistics button being pressed.
• Dim Output As String: Workhorse variable to prepare text to send out to ListBox display.
• Dim Average As Double = 0: Preset the Average variable to 0 for clarity.
• Dim Sum As Double = 0: The sum must start at 0, in order for the average calculation to work.
• Dim ScoreNumber as Integer: Variable used to index through the Scores array.
• Dim MinScore As Double = ScoreArray (0): Set the minimum value to the first value in the array.
• Dim MinScore As Double = ScoreArray (0): Set the maximum value to the first value in the array.
• lstDisplay .Items .Add (""): Add in a blank line in the ListBox display.
• For ScoreNumber =0 to NumberOfScores - 1: Create For Loop to index through all Quiz Scores entered.
• Sum+=ScoreArray (ScoreNumber): Sum each score in the array.
• If(MinScore >ScoreArray (ScoreNumber) ) then: Check if the present score is lower than the previous minimum value.
• MinScore = ScoreArray (ScoreNumber): Set New Minimum if lower.
• If(MaxScore < ScoreArray (ScoreNumber)) then: Check if the present score is higher than the previous maximum value.
• MaxScore = ScoreArray (ScoreNumber): Set the New Maximum if higher.
• If(NumberOfScores>0 ) then: Check to make sure we don't get a /0 error.
• Average = Sum/NumberOfScores: Calculate the average.
• Output ="Average: " + Average .ToString: Create text to output Average.
• lstDisplay .Items .Add (Output ): Display the Average.
• Output ="Minimum: " + MinScore .ToString: Create and Display Minimum value.
• Output ="Maximum: " + MaxScore .ToString: Create and Display Maximum value.

Since we should have a rough idea what's going on in the program, let's take this puppy out for a spin, and see what we get. We'll use the following data, and see if the program behaves as expected:

Keys Entered	Displayed Output
5 Enter	1. 5
6 Enter	1. 5 2. 6
7 Enter	1. 5 2. 6 3. 7
8 Enter	1. 5 2. 6 3. 7 4. 8
Clear Last	1. 5 2. 6 3. 7
Statistics	1. 5 2. 6 3. 7 Average: 6 Minimum: 5 Maximum: 7
Figure Array-10: Form At Run Time

Yup, kind of what we thought. If you're an ambitious type, you can press the Clear All and re-enter the data to make sure that the array resets. When you're done, you can catch up to the rest of us with the next exciting project: Parallel Arrays.

In order to continue this guide and work on that fascinating topic Parallel Arrays press the Button Below:

Home

Visual Basic

Windows Form App

Save Your Work

Exit Code

Button Event Code

Declare Variables

Math Class

Variable Scope

Loop Constructs

Do Until Loop

Exit Do | Exit For

Nested Loops

Arrays

Rnd( ) Function

KeyPressEventArgs

Parallel Arrays

Dynamic Arrays

ReDim Preserve

MultiDimensional Arrays

Length and Sort Methods

Structures