C# - Javascript Hash And Equivalent Algorithm?

Using this code on the javascript side and

Using sha As New SHA256Managed
Using memStream As New MemoryStream(Encoding.ASCII.GetBytes("Hello World!"))
Dim hash() As Byte = sha.ComputeHash(memStream)
Dim res As String = Encoding.Default.GetString(hash)
End Using
End Using

I have been unable to recreate the same hash for the same values with these two bits of code.

The javascript implementation returns: 7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069

and the vb.net example returns: ƒ�eñüS�-ÁH�Ö]ü-K�Öw(JÝÒ mi"

What am I missing? I assume it's something to do with the character encoding?

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