12 MustInherit Class C1
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15 Function F() Implements I.F
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19 MustInherit Class C2
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22 MustOverride Function F() Implements I.F
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26 MustInherit Class C3
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29 MustOverride Sub S() Implements I1.S
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40 Overrides Function F()
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55 Dim x As DC1 = New DC1()
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58 Dim y As DC2 = New DC2()
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62 Dim z As DC3 = New DC3()
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