Creating Connection String Manually

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VB

Windows

I want to create the connection string by selecting from ComboBoxes. I want to load DataSource in the First Combobox and accordingly load the second combobox with associated DataBase Name.
I am using SMO to do this .I managed to load first combobox with DataSource or Say Servernames and on this Selected Changed Event want to load the second Combo but I am getting error: Failed to Connect to the Server when event is fired. Where's The Problem.
My Code Follows :

Public Sub fetchDataSource()
        Dim dataTable = SmoApplication.EnumAvailableSqlServers(False)
        For i As Integer = 0 To dataTable.Rows.Count - 1
            cmbDataSource.Items.Add(dataTable.Rows(i).Item(0))

        Next
      
    End Sub
 Private Sub cmbDataSource_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbDataSource.SelectedIndexChanged
        cmbDatabase.Items.Clear()

        Dim serverName As String = cmbDataSource.SelectedText.ToString()
        Dim server As Server = New Server(serverName)

        For Each database As Database In server.Databases
            cmbDatabase.Items.Add(database.Name)
        Next
End Sub