Como: Definir um operador de conversão (Visual Basic)
If you have defined a class or structure, you can define a type conversion operator between the type of your class or structure and another data type (such as Integer, Double, or String).
Define the type conversion as a Função CType (Visual Basic) procedure within the class or structure. All conversion procedures must be Public Shared, and each one must specify either Expansão (Visual Basic) or Restrição (Visual Basic).
Defining an operator on a class or structure is also called overloading the operator.
Exemplo
The following example defines conversion operators between a structure called digit and a Byte.
Public Structure digit
Private dig As Byte
Public Sub New(ByVal b As Byte)
If (b < 0 OrElse b > 9) Then Throw New System.ArgumentException(
"Argument outside range for Byte")
Me.dig = b
End Sub
Public Shared Widening Operator CType(ByVal d As digit) As Byte
Return d.dig
End Operator
Public Shared Narrowing Operator CType(ByVal b As Byte) As digit
Return New digit(b)
End Operator
End Structure
You can test the structure digit with the following code.
Public Sub consumeDigit()
Dim d1 As New digit(4)
Dim d2 As New digit(7)
Dim d3 As digit = CType(CByte(3), digit)
Dim s As String = "Initial 4 generates " & CStr(CType(d1, Byte)) &
vbCrLf & "Initial 7 generates " & CStr(CType(d2, Byte)) &
vbCrLf & "Converted 3 generates " & CStr(CType(d3, Byte))
Try
Dim d4 As digit
d4 = CType(CType(d1, Byte) + CType(d2, Byte), digit)
Catch e4 As System.Exception
s &= vbCrLf & "4 + 7 generates " & """" & e4.Message & """"
End Try
Try
Dim d5 As digit = CType(CByte(10), digit)
Catch e5 As System.Exception
s &= vbCrLf & "Initial 10 generates " & """" & e5.Message & """"
End Try
MsgBox(s)
End Sub
Consulte também
Tarefas
Como: Definir um operador (Visual Basic)
Como: Chamar um procedimento de operador (Visual Basic)
Como: Usar uma classe que define operadores (Visual Basic)
Como: Declarar uma estrutura (Visual Basic)
Referência
Conceitos
Procedimentos de operador (Visual Basic)