I needed to implement the abstract member.
[Visual Basic]
Overrides Public Function Read( _
   ByVal b As Byte(), _
   ByVal off As Integer, _
   ByVal len As Integer _
) As Integer
[C#]
public override int Read(
   byte[] b,
   int off,
   int len
);
See Also
TarOutputStream Class | TarOutputStream Members | ICSharpCode.SharpZipLib.Tar Namespace