error when binding a maskedEd control to a property of a custom business class

I delcare my entity class:

public class address
{
private string postalCode="";

private string streetName="";

public string StreetName
{
get { return streetName;}
set { streetName=value;}
}
public string PostalCode
{
get { return postalCode;}
set { postalCode=value;}
}....etc

Then in my address form frmAddress I do: (TxtStrNam and TxtPostalCode re my 2 textboxes in the form. i know that s obvious) i do like this:

Public Class frmAddress

{

Dim oAddress As New address;

this.TxtStrNam.DataBindings.Add("Text", oAddress, "StreetName");

this.TxtPostalCode.DataBindings.Add("FormattedText", oAddress, "PostalCode");
.......etc

But I get an error: object reference not set to an nstance of an object in the line:

this.TxtPostalCode.DataBindings.Add("FormattedText", oAddress, "PostalCode");

That means my assignment to private variable: private string postalCode=""; is not working

2/ do u guys use maskedEd control to control user input or is there another method or better practice instead of using VB6 msmask.dll

Thanks a lot