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Problem with my Visual Basic Code

Hi EE'ers,

I am having some problems with my visual basic code. I am trying to write a liter conversion program (see code below). I am having problems getting the program to do the following:

1. When I hit the reset button the end up in the second box and I need the cursor to end in box 1.

2. If I enter an alpha character the program bombs out on me with the following error:

An unhandled exception of type 'System.InvalidCastException' occurred in microsoft.visualbasic.dll

Additional information: Cast from string "a" to type 'Double' is not valid.

I need the program to detect the null character....

I know that #2 need some type of IF ESLE THEN statement I am having trouble writing the correct statement.

Thanks,
BTW: I am new to VB

Public Class Form1
Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
Friend WithEvents GroupBox1 As System.Windows.Forms.GroupBox
Friend WithEvents Label1 As System.Windows.Forms.Label
Friend WithEvents GroupBox2 As System.Windows.Forms.GroupBox
Friend WithEvents Label2 As System.Windows.Forms.Label
Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
Friend WithEvents TextBox3 As System.Windows.Forms.TextBox
Friend WithEvents Label3 As System.Windows.Forms.Label
Friend WithEvents btnCompute As System.Windows.Forms.Button
Friend WithEvents btnReset As System.Windows.Forms.Button
Friend WithEvents btnQuit As System.Windows.Forms.Button
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
Me.TextBox1 = New System.Windows.Forms.TextBox
Me.btnCompute = New System.Windows.Forms.Button
Me.GroupBox1 = New System.Windows.Forms.GroupBox
Me.Label1 = New System.Windows.Forms.Label
Me.btnReset = New System.Windows.Forms.Button
Me.GroupBox2 = New System.Windows.Forms.GroupBox
Me.Label3 = New System.Windows.Forms.Label
Me.TextBox3 = New System.Windows.Forms.TextBox
Me.TextBox2 = New System.Windows.Forms.TextBox
Me.Label2 = New System.Windows.Forms.Label
Me.btnQuit = New System.Windows.Forms.Button
Me.GroupBox1.SuspendLayout()
Me.GroupBox2.SuspendLayout()
Me.SuspendLayout()
'
'TextBox1
'
Me.TextBox1.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.TextBox1.Location = New System.Drawing.Point(24, 56)
Me.TextBox1.Name = "TextBox1"
Me.TextBox1.TabIndex = 0
Me.TextBox1.Text = ""
'
'btnCompute
'
Me.btnCompute.Enabled = False
Me.btnCompute.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.btnCompute.Location = New System.Drawing.Point(24, 96)
Me.btnCompute.Name = "btnCompute"
Me.btnCompute.Size = New System.Drawing.Size(100, 32)
Me.btnCompute.TabIndex = 3
Me.btnCompute.Text = "Compute"
'
'GroupBox1
'
Me.GroupBox1.Controls.Add(Me.Label1)
Me.GroupBox1.Controls.Add(Me.btnReset)
Me.GroupBox1.Controls.Add(Me.btnCompute)
Me.GroupBox1.Controls.Add(Me.TextBox1)
Me.GroupBox1.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.GroupBox1.Location = New System.Drawing.Point(24, 16)
Me.GroupBox1.Name = "GroupBox1"
Me.GroupBox1.Size = New System.Drawing.Size(146, 192)
Me.GroupBox1.TabIndex = 4
Me.GroupBox1.TabStop = False
Me.GroupBox1.Text = "Enter Metric Value"
'
'Label1
'
Me.Label1.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.Label1.Location = New System.Drawing.Point(24, 32)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(100, 16)
Me.Label1.TabIndex = 5
Me.Label1.Text = "Liters:"
'
'btnReset
'
Me.btnReset.Enabled = False
Me.btnReset.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.btnReset.Location = New System.Drawing.Point(24, 144)
Me.btnReset.Name = "btnReset"
Me.btnReset.Size = New System.Drawing.Size(100, 30)
Me.btnReset.TabIndex = 4
Me.btnReset.Text = "Reset"
'
'GroupBox2
'
Me.GroupBox2.Controls.Add(Me.Label3)
Me.GroupBox2.Controls.Add(Me.TextBox3)
Me.GroupBox2.Controls.Add(Me.TextBox2)
Me.GroupBox2.Controls.Add(Me.Label2)
Me.GroupBox2.Location = New System.Drawing.Point(200, 16)
Me.GroupBox2.Name = "GroupBox2"
Me.GroupBox2.Size = New System.Drawing.Size(146, 192)
Me.GroupBox2.TabIndex = 5
Me.GroupBox2.TabStop = False
Me.GroupBox2.Text = "Equivalent English Value"
'
'Label3
'
Me.Label3.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.Label3.Location = New System.Drawing.Point(24, 104)
Me.Label3.Name = "Label3"
Me.Label3.Size = New System.Drawing.Size(100, 16)
Me.Label3.TabIndex = 3
Me.Label3.Text = "Gallons:"
'
'TextBox3
'
Me.TextBox3.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.TextBox3.Location = New System.Drawing.Point(24, 128)
Me.TextBox3.Name = "TextBox3"
Me.TextBox3.ReadOnly = True
Me.TextBox3.TabIndex = 2
Me.TextBox3.Text = ""
'
'TextBox2
'
Me.TextBox2.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.TextBox2.Location = New System.Drawing.Point(24, 56)
Me.TextBox2.Name = "TextBox2"
Me.TextBox2.ReadOnly = True
Me.TextBox2.TabIndex = 1
Me.TextBox2.Text = ""
'
'Label2
'
Me.Label2.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.Label2.Location = New System.Drawing.Point(24, 32)
Me.Label2.Name = "Label2"
Me.Label2.Size = New System.Drawing.Size(100, 16)
Me.Label2.TabIndex = 0
Me.Label2.Text = "Pints:"
'
'btnQuit
'
Me.btnQuit.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.btnQuit.Location = New System.Drawing.Point(136, 224)
Me.btnQuit.Name = "btnQuit"
Me.btnQuit.Size = New System.Drawing.Size(100, 30)
Me.btnQuit.TabIndex = 6
Me.btnQuit.Text = "Quit"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(369, 271)
Me.Controls.Add(Me.btnQuit)
Me.Controls.Add(Me.GroupBox2)
Me.Controls.Add(Me.GroupBox1)
Me.Name = "Form1"
Me.Text = "Metric to English Volume Conversion"
Me.GroupBox1.ResumeLayout(False)
Me.GroupBox2.ResumeLayout(False)
Me.ResumeLayout(False)

End Sub

#End Region

Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click

End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnQuit.Click
End
End Sub

Private Sub GroupBox1_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GroupBox1.Enter

End Sub

Private Sub btnCompute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCompute.Click
Dim inpLiter, equivPint, equivGallon 'This line creates the needed variables
inpLiter = TextBox1.Text 'Puts inputted Liter value in the inpLiter variable
equivPint = inpLiter * 2.113 'Converts inputted Liters into the equivalent Pints
equivGallon = inpLiter * 0.264125 'Converts inputted Liters into the equivalent Gallons
TextBox2.Text = equivPint 'Displays equivalent Pints in TextBox2
TextBox3.Text = equivGallon 'Displays equavalent Gallons in TextBox3
End Sub

Private Sub btnReset_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnReset.Click
TextBox1.Text = "" 'Clears data from TextBox1 (Input Liters)
TextBox2.Text = "" 'Clears data from TextBox2 (Equivalent Pints)
TextBox3.Text = "" 'Clears data from TextBox3 (Equivalent Gallons)
End Sub

Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
If TextBox1.Text = "" Then
btnCompute.Enabled = False 'Disables the Compute button before data is entered
btnReset.Enabled = False 'Disables the Reset button before data is entered
Else
btnCompute.Enabled = True 'Enables the Compute button when data is entered
btnReset.Enabled = True 'Enables the Reset button when data is entered
End If
End Sub

Private Sub GroupBox2_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GroupBox2.Enter

End Sub
End Class

ASKER CERTIFIED SOLUTION

Carl Tawn

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tqtclipper

ASKER

Thanks!!! I thought I tried everything.

tqtclipper

ASKER

For Question 2

What is I wanted the user to receive a error message say "Incorrect value" Please enter numeric value or something like that??

Carl Tawn

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress

If Not IsNumeric(e.KeyChar) Then
MsgBox "Incorrect value. Please enter a numeric value."
e.Handled = True
End If

End Sub

TRAY12

'Emty the contents of display boxes
Dim btnReset As String
Me.TextBox1.Clear()
Me.TextBox2.Clear()
Me.TextBox3.Clear()