Arithmetic operation resulted in an overflow. - vb.net

Question

I'm making a program that will remove the pain of hex editing an old DOS game (sensible world of soccer).
The program removes the limit of the number of players you can purchase (5), removes the maximum number of seasons you can compete for (20).
I'm trying to make it so you can edit your transfer budget too but i'm getting a Arithmetic operation resulted in an overflow. error when i run the code select the 50million option.
Here is the full code for my program (the transfer limit & maximum season limit both work):
Imports System.IO
Public Class Swos_Editor_2013
Dim transferbudget As String
Private Sub OpenToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles OpenToolStripMenuItem.Click
'#########
'#WARNING#
'#########
'Dim answer As DialogResult
'answer = MessageBox.Show("Make a Backup of your career file then click OK to proceed. I take no responsibility for damaged career files",
' "*PLEASE READ BEFORE PROCEEDING*", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
'##########################
'#Progress bar set options#
'##########################
ProgressBar1.Minimum = 0
ProgressBar1.Maximum = 2
ProgressBar1.Value = 0
'##################
'#tool tip options#
'##################
Dim toolTip1 As New ToolTip
toolTip1.AutoPopDelay = 5000
toolTip1.InitialDelay = 1000
toolTip1.ReshowDelay = 500
ToolTip1.ShowAlways = True
'###################################
'#Open Swos career file for editing#
'###################################
Me.OpenFileDialog1.InitialDirectory = "c:\"
Me.OpenFileDialog1.Title = "Select Career File for editing"
Me.OpenFileDialog1.DefaultExt = "*.car"
Me.OpenFileDialog1.FileName = ""
Me.OpenFileDialog1.Filter = "Career File(*.car)|*.car"
Me.OpenFileDialog1.Multiselect = False
'###################
'#OK button pressed#
'###################
If Me.OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
'##############################
'#increase progress bar to 50%#
'##############################
If ProgressBar1.Value < ProgressBar1.Maximum Then
ProgressBar1.Value += 1
End If
'################
'#Enable buttons#
'################
btn_save.Enabled = True
btn_trans_limit.Enabled = True
btn_career_limit.Enabled = True
cb_combo.Enabled = True
End If
End Sub
'#######################
'#Enable combo box drop#
'#######################
Private Sub cb_combo_CheckedChanged(ByVal sender As Object, e As EventArgs) Handles cb_combo.CheckedChanged
ComboBox1.Enabled = True
End Sub
'########################
'#Select Transfer Budget#
'########################
Private Sub ComboBox1_DropDownClosed(ByVal sender As Object, e As EventArgs) Handles ComboBox1.DropDownClosed
Select Case ComboBox1.SelectedItem
Case Is = "-£10 million (are you crazy CHALLENGE)"
transferbudget = "100"
Case Is = "-£2 million (mid level CHALLENGE)"
transferbudget = "200"
Case Is = "-£500k (lower league CHALLENGE)"
transferbudget = "500"
Case Is = "£500k (tough)"
transferbudget = "05"
Case Is = "£5 million"
transferbudget = "5"
Case Is = "£10 million"
transferbudget = "10"
Case Is = "£25 million"
transferbudget = "25"
Case Is = "£50 million"
transferbudget = "50000000"
Case Is = "£99 million"
transferbudget = "999"
End Select
End Sub
'#######################################
'#exit if EXIT is clicked from dropdown#
'#######################################
Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ExitToolStripMenuItem.Click
Me.Close()
End Sub
'#######################
'#Not got a bloody clue#
'#######################
Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, value As T) As T
target = value
Return value
End Function
'##################################################################
'#Apply changes made to drop down box AND radio button IF selected#
'##################################################################
Public Sub SaveChanges()
Dim amount As Integer
Dim fpath As String = OpenFileDialog1.FileName
Using stream = New FileStream(fpath, FileMode.Open, FileAccess.ReadWrite)
Dim result As Integer = 0
Dim buffer As Byte() = New Byte(3) {}
stream.Position = 54748
If (stream.Read(buffer, 0, 4) <> 4) Then
Throw New Exception(("Didn't read 4 bytes when it should have: " _
+ (result + "bytes read")))
End If
stream.Position = &HD5DC
buffer = BitConverter.GetBytes(amount)
stream.Write(buffer, 0, 4)
stream.Position = &HD880
If btn_career_limit.Checked Then
stream.WriteByte(0)
Else
stream.WriteByte(1)
End If
stream.Position = &HD5C4
If btn_trans_limit.Checked Then
stream.WriteByte(&HFF)
Else
stream.WriteByte(0)
End If
'stream.Write(buffer, 0, 4)
'stream.Position = &HD5DC
'If testbutton.Checked Then
' stream.WriteByte("3B9AC9FF")
'End If
**If cb_combo.Checked = True Then
stream.Position = &HD5DC
stream.WriteByte(transferbudget) ######this is where i get the overflow error#####**
End If
End Using
End Sub
'###############################################
'#Save above changes & set progress bar to 100%#
'###############################################
Private Sub btn_save_Click(sender As Object, e As EventArgs) Handles btn_save.Click
SaveChanges()
If ProgressBar1.Value < ProgressBar1.Maximum Then
ProgressBar1.Value += 1
End If
End Sub
'#########################################################################################################################################
'# TOOL TIP (MOUSE HOVER) #
'# #
Private Sub btn_trans_limit_CheckedChanged(sender As Object, e As EventArgs) Handles btn_trans_limit.MouseHover
'#
ToolTip1.SetToolTip(btn_trans_limit, "Removes 5 player transfer limit") '#
End Sub
Private Sub btn_career_limit_CheckedChanged(sender As Object, e As EventArgs) Handles btn_career_limit.MouseHover '#
'# '#
ToolTip1.SetToolTip(btn_career_limit, "Removes 20 season limit") '#
End Sub
Private Sub ComboBox1_MouseHover(sender As Object, e As EventArgs) Handles ComboBox1.MouseHover '#
'# '#
ToolTip1.SetToolTip(ComboBox1, "Select Transfer Budget") '#
End Sub
Private Sub btn_save_MouseHover(sender As Object, e As EventArgs) Handles btn_save.MouseHover '#
'# '#
ToolTip1.SetToolTip(btn_save, "Save changes to your career file")
End Sub
Private Sub cb_combo_MouseHover(sender As Object, e As EventArgs) Handles cb_combo.MouseHover '#
'# '#
ToolTip1.SetToolTip(cb_combo, "tick if you want to edit transfer budget") '#
End Sub
'#########################################################################################################################################
End Class
Any help would be greatly appreciated.

Answer 1

You are passing a String (transferbudget) into the FileStream.WriteByte method. The WriteByte method takes a Byte, not a String. If you had Option Strict On, as you should, this would result in a compile error. However, since you have Option Strict Off, it allows you to compile and just automatically inserts the type conversion from String to Byte for you. The type conversion operation will throw an overflow exception if the value in the string is outside of the minimum and maximum value of a Byte (0 - 255). Here's the code where you set the transferbudget variable:
Select Case ComboBox1.SelectedItem
Case Is = "-£10 million (are you crazy CHALLENGE)"
transferbudget = "100"
Case Is = "-£2 million (mid level CHALLENGE)"
transferbudget = "200"
Case Is = "-£500k (lower league CHALLENGE)"
transferbudget = "500" 'GAH!
Case Is = "£500k (tough)"
transferbudget = "05"
Case Is = "£5 million"
transferbudget = "5"
Case Is = "£10 million"
transferbudget = "10"
Case Is = "£25 million"
transferbudget = "25"
Case Is = "£50 million"
transferbudget = "50000000" 'GAH!
Case Is = "£99 million"
transferbudget = "999" 'GAH!
End Select
As you can see, there are several values there that are greater than 255.