How do I limit the values I can save? - string

Question

I'm currently working on a Registration form where all the details of a student are save in a text file.
In one of my fields, I have a combobox list of all the school he/she can select.
I populated the combobox using a textfile.
The format of these values are for example: (code~school name) SCH001~Saint Thomas College
Question - how do I limit the values I can save?
example - I want only the school code to be saved without the name of school: SCH001
Here's how I save the fields in a text file:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnRegister.Click
Dim firstname, lastname, email, mobile, level, currentschool, currenttrack, institution1, institution2, institution3, institution4, institution5, institution6, courses1, courses2, courses3 As String
firstname = txtFName.Text
lastname = txtLName.Text
email = txtEmail.Text
mobile = txtMobile.Text
level = cmbLevel.Text
currentschool = cmbCurrentSchool.Text
currenttrack = cmbCurrentTrack.Text
institution1 = cmbInstitution1.Text
institution2 = cmbInstitution2.Text
institution3 = cmbInstitution3.Text
institution4 = cmbInstitution4.Text
institution5 = cmbInstitution5.Text
institution6 = cmbInstitution6.Text
courses1 = cmbCourse1.Text
courses2 = cmbCourse2.Text
courses3 = cmbCourse3.Text
Using sw As StreamWriter = File.AppendText("C:\Users\jmrosales\Documents\RegistrationForm\Registered.txt")
sw.WriteLine(firstname & "~" & lastname & "~" & email & "~" & mobile & "~" & level & "~" & currentschool & "~" & currenttrack & "~" & institution1 & "~" & institution2 & "~" & institution3 & "~" & institution4 & "~" & institution5 & "~" & institution6 & "~" & courses1 & "~" & courses2 & "~" & courses3)
End Using
MsgBox("Registration Complete!")
End Sub
I hope you guys understand what i'm trying to say.
I'm just new here.

Answer 1

You can do this in two ways:
Using .Split()
Using .Substring()
Using .Split()
Here's what your code will look like:
currentschool = cmbCurrentSchool.Text.Split("~")
This will return two strings, "SCH001" and "Saint Thomas College".
But since you need only the Code, put (0) at the end of the code above:
currentschool = cmbCurrentSchool.Text.Split("~")(0)
Further you can add c in the above snippet like:
currentschool = cmbCurrentSchool.Text.Split("~"c)(0)
This would specify ~ is a character.
using .Substring()
This will only work if it's sure that your code will always be 6 character (3 for SCH and rest 3 for the number-code)
currentschool = cmbCurrentSchool.Text.Substring(0,6)
Here, 0 means start picking the character from 1st position and 6 means get six characters to get a new string.
Hope this helps :)

Answer 2

Presuming that the school code would follow exactly 6 characters as in this SCH001~Saint Thomas College, you can use Substring:
currentschool = cmbCurrentSchool.Text.Substring(0,6) '6 means 6 characters to be cut from cmbCurrentSchool to currentschool
If here currentschool stores the schoolcode.
Else, you can use Split:
currentschool = cmbCurrentSchool.Text.Split("~")(0)

Answer 3

The most simple answer would be to split the string at ~ and just return the part you need:
If cmbCurrentSchool.Text.Contains("~") Then 'A check to avoid possible errors.
currentschool = cmbCurrentSchool.Text.Split("~"c)(0) '0 means that we should get the first item of the array, thus "SCH001".
Else
currentschool = cmbCurrentSchool.Text
End If
cmbCurrentSchool.Text.Split("~"c) will return an array of two strings:
"SCH001~Saint Thomas College" -> {"SCH001", "Saint Thomas College"}
Documentation:
String.Split() method