check for uniqueness of employee id number - vb.net

Question

Cant seem to figure out how to check for a unique Employee id Number. I know the validation has to go in the form load, just not sure how to go about it.
Public Class Form1
Dim filename As String
Dim dataFile As System.IO.File
Dim dataWrite As System.IO.StreamWriter
''LOADING AND WRITE TO TEXT DOCUMENT
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'asks user for file name
filename = InputBox("Enter output file name")
If IO.File.Exists(filename) Then
dataWrite = IO.File.AppendText(filename)
Else
MessageBox.Show("filename does not exist")
filename = InputBox("Enter output file name")
dataWrite = IO.File.CreateText(filename)
End If
cboDepart.Items.Add("Accounting")
cboDepart.Items.Add("Administration")
cboDepart.Items.Add("Marketing")
cboDepart.Items.Add("MIS")
cboDepart.Items.Add("Sales")
End Sub
'------
Public EMPLOYEEIDS As String
Dim employeeID1 As ServerData()
Dim employeeID2 As ServerData()
Dim reader As String = My.Computer.FileSystem.ReadAllText("servers.lst")
Dim s() As String
Dim Totalemployeeids As String = CStr(reader.Length)
Dim x As Integer = 0
Dim myArray As String() = reader.Split("|"c)
For x = 1 To Totalemployeeids
employeeID1(x).ServerName = myArray(0)
employeeID2(x).IDname = myarray(0)
Form1_load.ListBox1.Items.Add(Servers(x).ServerName)
x += 1
Next
Structure ServerData
End Structure
End Class

Answer 1

You usually do not insert a unique ID from the client side. Instead, it is inserted automatically by the database server. There is a way to retrieve an inserted ID back, if you need it for display (can also act as a confirmation that a record was successfully inserted):
SELECT SCOPE_IDENTITY()
An example is shown in this answer:
How to get last inserted id? (C#)
On the client side, you need to implement insertion of everything but the ID, in this case you don't need to check for uniqueness. There may be other validation issues upon commit though (unique key violation, data type mismatch) - make sure you catch exceptions and display them to the user as appropriate.