How to remove special character from string?

Visual basic programming problem. I have code but I can't get my .remove command to work and need help.?

• Majority of the code works properly. It adds the numbers correctly but I can remove the 5th character and I need help. Public Class frmVitaCredit Private Sub btnCalculate_Click(sender As System.Object, e As System.EventArgs) Handles btnCalculate.Click Dim cardNumber As Integer, firstDigit As Integer, secondDigit As Integer, thirdDigit As Integer, fourthDigit As Integer, fullNumber As Integer 'If input is null/empty then print an error message If String.IsNullOrEmpty(txtInput.Text) Then MsgBox("Please enter the first 4 digits of the card number") txtInput.Focus() Return End If 'If input is not numeric then print an error message If Not IsNumeric(txtInput.Text) Then MsgBox("Input must be numeric") txtInput.SelectAll() txtInput.Focus() Return End If 'if input is not of length 4 then print an error message If Len(txtInput.Text) <> 4 Then MsgBox("Input must be of 4 digits") txtInput.SelectAll() txtInput.Focus() Return End If 'Convert string to number cardNumber = CInt(txtInput.Text) 'Extract the 4 digits from the input firstDigit = cardNumber \ 1000 secondDigit = (cardNumber \ 100) Mod 10 thirdDigit = (cardNumber \ 10) Mod 10 fourthDigit = cardNumber Mod 10 'determine the full card number fullNumber = CInt(txtInput.Text + CStr(firstDigit + secondDigit * 2 + thirdDigit + fourthDigit * 2)) txtCardNum.Text = CStr(fullNumber) Dim fullnumber As String = ###### fullNumber = fullNumber.Remove(4, 1) End Sub End Class

• Answer:

  where is the problem?