Checking content of textbox vb.net - asp.net

Question

I am using a text box for input to my SQL query. Based on the input I create a certain query and display the data in a gridview.
However I wish to make an adjustment for my users.
They often make an input like PL26... However this is not a valid name in the database to search for. Therefore I want to CHECK their input, and alter it accordingly, so they don't have to think about it.
I happen to know that when they type PL26 the correct input would be PL000026 ... The entity to search for is always "PL" + 6 characters/numbers... so if they wrote PL155, the number/string I pass to the sql query should become PL + 000 + 155 = PL000155.
I hope someone can help me how to accomplish this. That is if it is possible?
My idea/Pseudo code would be something like
If tbInput.txt's FIRST 2 CHARS are PL, then check total length of string
if StringLength < 8 characters, then
if length = 2 then ADD 4 0' after PL...
if length = 3 then add 3 0's after PL...
if length = 3 then add 3 0's after PL..
etc
....
...

Answer 1

Here we go:
Private Sub Button21_Click(sender As System.Object, e As System.EventArgs) Handles Button21.Click
Debug.Print(formatCode("PL1"))
Debug.Print(formatCode("PL"))
Debug.Print(formatCode("PL01"))
Debug.Print(formatCode("PL155"))
End Sub
Private Function formatCode(userInput As String) As String
Dim returnVal As String
If userInput.Length < 8 Then
returnVal = String.Concat(userInput.Substring(0, 2), userInput.Substring(2, userInput.Length - 2).PadLeft(6, "0"))
Else
returnVal = userInput
End If
Return returnVal
End Function
You may need to add some validation ensuring it starts with PL etc.

Answer 2

The following will work as long as there are no other non-numeric characters in between the PL and the numbers. You can always add it in your validation.
Dim newInput As String
If (input.StartsWith("PL")) Then
input = input.Remove(0, 2)
End If
' If this fails then it means the input was not valid
Dim numberPart = Convert.ToInt32(input)
newInput = "PL" + numberPart.ToString("D6")

Answer 3

Exctract a number by removing prefix "PL"
Parse to Integer
Use Custom Numeric Format Strings(zero placeholder) for adding zeros and prefix
Const PREFIX As String = "PL"
Dim exctractedNumber As Int32
If Int32.TryParse(tbInput.txt.Replace(PREFIX, String.Empty), exctractedNumber) = False Then
'Error nahdling
Exit Sub
End If
Dim finalFormat As String = String.Format("'{0}'000000", PREFIX)
Dim finalValue As String = exctractedNumber.ToString(finalFormat)

Answer 4

I would make use of the handy PadLeft method:
Dim input As String = "PL26"
Dim number As String = input.Substring(2, input.Length - 2)
If number.Length <> 6 Then
number = number.PadLeft(6, "0"C)
End If
MSDN String.PadLeft