sed -i -r "s/ Class w(w|d)+/ Class C$(python -c 'import uuid;print(uuid.uuid4().hex)')/"

Public Class Class1
    Public ReadOnly Property P As String = "hello"
End Class

Public Class Class2
    Public ReadOnly Property P As String = "hello"
End Class

$ awk '{gsub(/Class [[:alnum:]]+/, "Class C" int(9999*rand()))} 1' Class1.vb
Public Class C2377
    Public ReadOnly Property P As String = "hello"
End Class

Public Class C5854
    Public ReadOnly Property P As String = "hello"
End Class

awk -v s=$RANDOM 'BEGIN{srand(s)} {gsub(/Class [[:alnum:]]+/, "Class C" int(9999*rand()))} 1' Class1.vb