SecurityException was unhandled by user code – VSTA, C#, InfoPath 2007

I got this error, while I was developing a InfoPath form in VSTA (Visual Studio Tools for Applications 2008) . This was my enviornment:

• Windows 7
• VSTA 2008
• InfoPath 2007

Scenario: I was trying to get the user information from Active Directory(AD) and then display in an InfoPath form. Here is the C# code I have written in the VSTA:

public void CTRL1_5_Clicked(object sender, ClickedEventArgs e)
 {
 string strUserName = System.Environment.UserName;

 string xpath2 = "/my:myFields/my:field1";
 XPathNavigator field2 = MainDataSource.CreateNavigator().SelectSingleNode(xpath2, NamespaceManager);
 field2.SetValue(GetOU(strUserName)); //Get Organization Unit(OU) from Acitve Directory(AD)
 }

This is the error message I have got: :(

Solution: I have fixed this issue in a different situation, just read in my previous post.

Thanks. R./

Happy InfoPathing. :)