All string literals in VB.NET are verbatim string literals. Simply write
Dim str As String = "c:\folder1\file1.txt"
VB.NET doesn’t support inline control characters. So backslashes are always interpreted literally.
The only character that needs to be escaped is the double quotation mark, which is escaped by doubling it, as you do in C#
Dim s As String = """Ahoy!"" cried the captain." ' "Ahoy!" cried the captain.