Using Textbox.Text in Connection String VB.NET 2008

[condonethis]

Using the following code and trying to allow the end user to specify the values for the connection string for an app that inports .csv to a specified location. App fails to run due to the fact that it tries to initialize connection string on program run resulting in NULL values. Is there any way I can prevent this and make this work?

Imports System.Data.SqlClient
Imports System.IO
Imports System.Configuration
Imports System.Data.Common.DbConnection
 
Public Class csvUpdate
 
    'connection string
    Public WithEvents con As New SqlConnection _
 ("Data Source=" + TxtServer.Text + ";Initial Catalog=" + TxtCat.Text + ";Integrated Security=True;Asynchronous Processing=True")
 
    Public WithEvents var As New SqlConnection _
   ("Data Source=" + TxtServer.Text + ";Initial Catalog=" + TxtCat.Text + ";User Id =" + TxtUser.Text + ";Password=" + TxtPass.Text + ";Asynchronous Processing=True")
 
 
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Height = 172
    End Sub
 
   
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnCSV.Click
        If TxtTable.Text <> "" Then
            OpenFileDialog1.Title = "Open a Text File"
            OpenFileDialog1.Filter = "Comma Delimited(*.csv)|*.csv"
            OpenFileDialog1.DefaultExt = ".csv"
            OpenFileDialog1.InitialDirectory = "C:\"
            OpenFileDialog1.ShowDialog()
            If ChkAD.Checked = True Then
                'readcsvAD()
            Else
                'readcsvUP()
            End If
        Else
            TxtTable.Focus()
        End If
    End Sub
 
    Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ChkAD.CheckedChanged
 
        If Me.Height < 242 Then
            Me.Height = 243
        Else
            Me.Width = 144
            Me.Height = 172
        End If
 
    End Sub
End Class

Thanks!