Why Encoding.Default.GetBytes() Returns Different Results In C#

We recently came across some sample code from a vendor for hashing a secret key for a web service call, their sample was in VB.NET which we converted to C#. This caused the hashing to produce different input. It turns out the way they were generating the key for the encryption was by converting a char array to a string and back to a byte array. This led me to the discovery that VB.NET and C#'s default encoder work differently with some characters.

C#:
Console.Write(Encoding.Default.GetBytes(new char[] { (char)149 })[0]);

VB:
Dim b As Char() = {Chr(149)}
Console.WriteLine(Encoding.Default.GetBytes(b)(0))

The C# output is 63, while VB is the correct byte value of 149.if you use any other value, like 145, etc, the output matches.Walking through the debugging, both VB and C# default encoder is SBCSCodePageEncoding.I have corrected the sample code by directly initializing a byte array, which it should have been in the first place, but I still want to know why the encoder, which should not be language specific, appears to be just that.