whats the meaning of this sytax in VB "If(a & b)"

I'm trying to translate a certain code to c#.

Basically I understand most of the code I'm dealing with, and even the intent of the original code. but I wanna be sure I have all my bases covered.

its the 5th post in this topic: http://ift.tt/1SdJclR by user Kresimir

the code at question:

Dim ret As Integer = User32DLL.GetWindowLong(Me.Handle, -16)
Dim s As String = String.Empty
If (ret And WS_BORDER) Then s &= "WS_BORDER" & NewLine

I do not understand what the "If (ret And WS_BORDER)" statement is supposed to do, and how to translate it to C#

is it:

    if (ret!=null & WS_BORDER!=null)

or something else?

Thank you.