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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

Instrução Operator

Instrução Structure

Conceitos

Procedimentos de operador (Visual Basic)

Conversões explícitas e implícitas (Visual Basic)

Conversões de expansão e restrição (Visual Basic)