connect sqlserver through app.config

<connectionStrings>
  <add 
        name = "DBCS"
        connectionString="Data Source=USER1-PC\sqlexpress;Initial Catalog=Test;Integrated Security=True"
        providerName="System.Data.SqlClient" />
< /connectionStrings >

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
Imports System.Data.Sql

Public Class Form1
  Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("DBCS").ConnectionString)
  
  Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    Try
      con.Open()

      Dim cmd As String
      cmd = "select * from tblemp"

      Dim da As New SqlDataAdapter(cmd, con)
      Dim ds As New DataSet

      da.Fill(ds, "tblemp")
      con.Close()
      DataGridView1.DataSource = ds.Tables("tblemp")

    Catch ex As Exception
      MessageBox.Show(ex.Message)
    End Try
  End Sub
End Class