VB Question

Hi,

Have some code here:

It reads a file for employee numbers and loads them to a list, and if a user tried to enter a duplicate one, an error would populate.

Say employee numbers 1,2,3,4,5 are in the file.

Then I try to add 5, it would call an error. But if I add 6, it goes right in since it is not there. The problem is when I don't leave the form and add 6 again. The record will be added since It's not part of the list. When I write the record to the file, I want to have something that will also add the txtEmployeeNumber.text to the empNum list that is in the load part. So if I were to add 6 in again, there would be an error.

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        'Read File And Store Employee Numbers
        empNumList = New List(Of String)
        Dim strfileName As String = "text.txt"
        Dim empNum As String = txtEmployeeNumber.Text

        Dim Lines As String() = File.ReadAllLines(strFileName)
        'Dim Found As Boolean = False
        For i As Integer = 3 To Lines.Length - 1 Step 11
            empNumList.Add(Lines(i))
            i -= 1
        Next
        For j As Integer = 0 To empNumList.Count - 1
            Console.WriteLine(empNumList(j))
        Next
    End Sub    
	
	Private Sub txtEmployeeNumber_LostFocus(sender As Object, e As EventArgs) Handles txtEmployeeNumber.LostFocus
        'Check For Duplicate Employee Numbers
        Dim Found As Boolean = False
        Dim empNum = txtEmployeeNumber.Text
        For i As Integer = 0 To empNumList.Count - 1
            If empNumList(i).Equals(empNum) Then
                found = True
                Exit For
            End If
        Next
        If Found Then
            'Show Error If Dupicate
            MessageBox.Show("Employee Id Already Entered" & vbCrLf & _
                                "Please Enter A Unique Employee Number")
            txtEmployeeNumber.Text = ""
            txtEmployeeNumber.Focus()
        Else
        End If
    End Sub
	
	           
  Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
      
                'Will Append To Current File Instead Of Create It From Scratch Again
                employeeFile = File.AppendText(strFileName)
                employeeFile.WriteLine(strFirstName)
                employeeFile.WriteLine(strMiddleName)
                employeeFile.WriteLine(strLastName)
                employeeFile.WriteLine(txtEmployeeNumber.Text)
                employeeFile.WriteLine(strDepartment)
                employeeFile.WriteLine(strTelephone)
                employeeFile.WriteLine(txtExtension.Text)
                employeeFile.WriteLine(strEmail)
                employeeFile.WriteLine(intBaseSalary)
                employeeFile.WriteLine()
                'File Will Close After Every Added Record
                employeeFile.Close()
                'Display Message Box When Data Is Entered, Then Clear For New Data
                MessageBox.Show("Data Entered Successfully")
                Clear_Stuff()
            Catch
                'Display Error If There Is A Problem With File (For Extra Measures)
                MessageBox.Show("File Can't Be Written To")
            End Try
        End If
		End Sub

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