當試圖從基類轉換爲子類VB.NET轉換問題（BC30311：「類型‘<type1>’的值不能被轉換爲‘<type2>’」）

Question

請看看下面的代碼：

Public Sub Method(Of TEntity As EntityObject)(ByVal entity As TEntity) 
    If TypeOf entity Is Contact Then 
     Dim contact As Contact = entity 'Compile error' 
     Dim contact = DirectCast(entity, Contact) 'Compile error' 
     Dim contact = CType(entity, Contact) 'Compile error' 
    End If 
End Sub 

任何想法？

Answer 1

下列任一作品之一，我想我會用第一種：

Dim contact As Contact = DirectCast(entity, Object) 
Dim contact As Contact = Convert.ChangeType(entity, TypeCode.Object) 

Answer 2

這不應該給你一個編譯錯誤，並應適當地將它轉換爲你正在尋找的類型：

Dim contact As Contact = TryCast(entity, Contact)