Type Conversion in the .NET Framework

' Convert an Int32 value to a Decimal (a widening conversion). 
Dim integralValue As Integer = 12534
Dim decimalValue As Decimal = Convert.ToDecimal(integralValue)
Console.WriteLine("Converted the {0} value {1} to the {2} value {3:N2}.", 
                  integralValue.GetType().Name,
                  integralValue,
                  decimalValue.GetType().Name,
                  decimalValue)

' Convert a Byte value to an Int32 value (a widening conversion). 
Dim byteValue As Byte = Byte.MaxValue
Dim integralValue2 As Integer = Convert.ToInt32(byteValue)                                  
Console.WriteLine("Converted the {0} value {1} to " + 
                                  "the {2} value {3:G}.",
                                  byteValue.GetType().Name,
                                  byteValue,
                                  integralValue2.GetType().Name,
                                  integralValue2)

' Convert a Double value to an Int32 value (a narrowing conversion). 
Dim doubleValue As Double = 16.32513e12
Try 
   Dim longValue As Long = Convert.ToInt64(doubleValue)
   Console.WriteLine("Converted the {0} value {1:E} to " + 
                                     "the {2} value {3:N0}.",
                                     doubleValue.GetType().Name,
                                     doubleValue,
                                     longValue.GetType().Name,
                                     longValue)
Catch e As OverflowException
   Console.WriteLine("Unable to convert the {0:E} value {1}.",
                                     doubleValue.GetType().Name, doubleValue)
End Try                                                              

' Convert a signed byte to a byte (a narrowing conversion).      
Dim sbyteValue As SByte = -16
Try 
   Dim byteValue2 As Byte = Convert.ToByte(sbyteValue)
   Console.WriteLine("Converted the {0} value {1} to " + 
                                     "the {2} value {3:G}.",
                                     sbyteValue.GetType().Name,
                                     sbyteValue,
                                     byteValue2.GetType().Name,
                                     byteValue2)
Catch e As OverflowException
   Console.WriteLine("Unable to convert the {0} value {1}.",
                                     sbyteValue.GetType().Name, sbyteValue)
End Try  
' The example displays the following output: 
'       Converted the Int32 value 12534 to the Decimal value 12,534.00. 
'       Converted the Byte value 255 to the Int32 value 255. 
'       Converted the Double value 1.632513E+013 to the Int64 value 16,325,130,000,000. 
'       Unable to convert the SByte value -16.                                                                  

Dim doubleValue As Double  

' Convert a Double to a Decimal. 
Dim decimalValue As Decimal = 13956810.96702888123451471211d
doubleValue = Convert.ToDouble(decimalValue)
Console.WriteLine("{0} converted to {1}.", decimalValue, doubleValue)

doubleValue = 42.72
Try 
   Dim integerValue As Integer = Convert.ToInt32(doubleValue)
   Console.WriteLine("{0} converted to {1}.",
                                     doubleValue, integerValue)
Catch e As OverflowException
   Console.WriteLine("Unable to convert {0} to an integer.",
                                     doubleValue)
End Try    
' The example displays the following output: 
'       13956810.96702888123451471211 converted to 13956810.9670289. 
'       42.72 converted to 43.

Public MustInherit Class Temperature
   Implements IConvertible

   Protected temp As Decimal 

   Public Sub New(temperature As Decimal)
      Me.temp = temperature
   End Sub 

   Public Property Value As Decimal 
      Get  
         Return Me.temp
      End Get 
      Set 
         Me.temp = Value
      End Set    
   End Property 

   Public Overrides Function ToString() As String 
      Return temp.ToString() & "º" 
   End Function 

   ' IConvertible implementations. 
   Public Function GetTypeCode() As TypeCode Implements IConvertible.GetTypeCode
      Return TypeCode.Object 
   End Function    

   Public Function ToBoolean(provider As IFormatProvider) As Boolean Implements IConvertible.ToBoolean
      Throw New InvalidCastException(String.Format("Temperature-to-Boolean conversion is not supported."))
   End Function 

   Public Function ToByte(provider As IFormatProvider) As Byte Implements IConvertible.ToByte
      If temp < Byte.MinValue Or temp > Byte.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the Byte data type.", temp))
      Else 
         Return CByte(temp)
      End If     
   End Function 

   Public Function ToChar(provider As IFormatProvider) As Char Implements IConvertible.ToChar
      Throw New InvalidCastException("Temperature-to-Char conversion is not supported.")
   End Function 

   Public Function ToDateTime(provider As IFormatProvider) As DateTime Implements IConvertible.ToDateTime
      Throw New InvalidCastException("Temperature-to-DateTime conversion is not supported.")
   End Function 

   Public Function ToDecimal(provider As IFormatProvider) As Decimal Implements IConvertible.ToDecimal
      Return temp
   End Function 

   Public Function ToDouble(provider As IFormatProvider) As Double Implements IConvertible.ToDouble
      Return CDbl(temp)
   End Function 

   Public Function ToInt16(provider As IFormatProvider) As Int16 Implements IConvertible.ToInt16
      If temp < Int16.MinValue Or temp > Int16.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the Int16 data type.", temp))
      End If 
      Return CShort(Math.Round(temp))
   End Function 

   Public Function ToInt32(provider As IFormatProvider) As Int32 Implements IConvertible.ToInt32
      If temp < Int32.MinValue Or temp > Int32.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the Int32 data type.", temp))
      End If 
      Return CInt(Math.Round(temp))
   End Function 

   Public Function ToInt64(provider As IFormatProvider) As Int64 Implements IConvertible.ToInt64
      If temp < Int64.MinValue Or temp > Int64.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the Int64 data type.", temp))
      End If 
      Return CLng(Math.Round(temp))
   End Function 

   Public Function ToSByte(provider As IFormatProvider) As SByte Implements IConvertible.ToSByte
      If temp < SByte.MinValue Or temp > SByte.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the SByte data type.", temp))
      Else 
         Return CSByte(temp)
      End If     
   End Function 

   Public Function ToSingle(provider As IFormatProvider) As Single Implements IConvertible.ToSingle
      Return CSng(temp)
   End Function 

   Public Overridable Overloads Function ToString(provider As IFormatProvider) As String Implements IConvertible.ToString
      Return temp.ToString(provider) & " °C" 
   End Function 

   ' If conversionType is a implemented by another IConvertible method, call it. 
   Public Overridable Function ToType(conversionType As Type, provider As IFormatProvider) As Object Implements IConvertible.ToType
      Select Case Type.GetTypeCode(conversionType)
         Case TypeCode.Boolean 
            Return Me.ToBoolean(provider)
         Case TypeCode.Byte 
            Return Me.ToByte(provider)
         Case TypeCode.Char 
            Return Me.ToChar(provider)   
         Case TypeCode.DateTime
            Return Me.ToDateTime(provider)
         Case TypeCode.Decimal 
            Return Me.ToDecimal(provider)
         Case TypeCode.Double 
            Return Me.ToDouble(provider)
         Case TypeCode.Empty
            Throw New NullReferenceException("The target type is null.")
         Case TypeCode.Int16
            Return Me.ToInt16(provider)
         Case TypeCode.Int32
            Return Me.ToInt32(provider)
         Case TypeCode.Int64
            Return Me.ToInt64(provider)
         Case TypeCode.Object 
            ' Leave conversion of non-base types to derived classes. 
            Throw New InvalidCastException(String.Format("Cannot convert from Temperature to {0}.", _
                                           conversionType.Name))
         Case TypeCode.SByte 
            Return Me.ToSByte(provider)
         Case TypeCode.Single 
            Return Me.ToSingle(provider)
         Case TypeCode.String 
            Return Me.ToString(provider)
         Case TypeCode.UInt16
            Return Me.ToUInt16(provider)
         Case TypeCode.UInt32
            Return Me.ToUInt32(provider)
         Case TypeCode.UInt64
            Return Me.ToUInt64(provider)
         Case Else 
            Throw New InvalidCastException("Conversion not supported.")   
      End Select 
   End Function 

   Public Function ToUInt16(provider As IFormatProvider) As UInt16 Implements IConvertible.ToUInt16
      If temp < UInt16.MinValue Or temp > UInt16.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the UInt16 data type.", temp))
      End If 
      Return CUShort(Math.Round(temp))
   End Function 

   Public Function ToUInt32(provider As IFormatProvider) As UInt32 Implements IConvertible.ToUInt32
      If temp < UInt32.MinValue Or temp > UInt32.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the UInt32 data type.", temp))
      End If 
      Return CUInt(Math.Round(temp))
   End Function 

   Public Function ToUInt64(provider As IFormatProvider) As UInt64 Implements IConvertible.ToUInt64
      If temp < UInt64.MinValue Or temp > UInt64.MaxValue Then 
         Throw New OverflowException(String.Format("{0} is out of range of the UInt64 data type.", temp))
      End If 
      Return CULng(Math.Round(temp))
   End Function 
End Class 

Public Class TemperatureCelsius : Inherits Temperature : Implements IConvertible
   Public Sub New(value As Decimal)
      MyBase.New(value)
   End Sub 

   ' Override ToString methods. 
   Public Overrides Function ToString() As String 
      Return Me.ToString(Nothing)
   End Function 

   Public Overrides Function ToString(provider As IFormatProvider ) As String 
      Return temp.ToString(provider) + "°C"  
   End Function 

  ' If conversionType is a implemented by another IConvertible method, call it. 
   Public Overrides Function ToType(conversionType As Type, provider As IFormatProvider) As Object 
      ' For non-objects, call base method. 
      If Type.GetTypeCode(conversionType) <> TypeCode.Object Then 
         Return MyBase.ToType(conversionType, provider)
      Else    
         If conversionType.Equals(GetType(TemperatureCelsius)) Then 
            Return Me 
         ElseIf conversionType.Equals(GetType(TemperatureFahrenheit))
            Return New TemperatureFahrenheit(CDec(Me.temp * 9 / 5 + 32))
         ' Unspecified object type: throw an InvalidCastException. 
         Else 
            Throw New InvalidCastException(String.Format("Cannot convert from Temperature to {0}.", _ 
                                           conversionType.Name))
         End If 
      End If                                   
   End Function 
End Class 

Public Class TemperatureFahrenheit : Inherits Temperature : Implements IConvertible
   Public Sub New(value As Decimal)
      MyBase.New(value)
   End Sub 

   ' Override ToString methods. 
   Public Overrides Function ToString() As String 
      Return Me.ToString(Nothing)
   End Function 

   Public Overrides Function ToString(provider As IFormatProvider ) As String 
      Return temp.ToString(provider) + "°F"  
   End Function 

   Public Overrides Function ToType(conversionType As Type, provider As IFormatProvider) As Object 
      ' For non-objects, call base methood. 
      If Type.GetTypeCode(conversionType) <> TypeCode.Object Then 
         Return MyBase.ToType(conversionType, provider)
      Else    
         ' Handle conversion between derived classes. 
         If conversionType.Equals(GetType(TemperatureFahrenheit)) Then  
            Return Me 
         ElseIf conversionType.Equals(GetType(TemperatureCelsius))
            Return New TemperatureCelsius(CDec((MyBase.temp - 32) * 5 / 9))
         ' Unspecified object type: throw an InvalidCastException. 
         Else 
            Throw New InvalidCastException(String.Format("Cannot convert from Temperature to {0}.", _
                                           conversionType.Name))
         End If 
      End If                                   
   End Function 
End Class

Dim tempC1 As New TemperatureCelsius(0)
Dim tempF1 As TemperatureFahrenheit = CType(Convert.ChangeType(tempC1, GetType(TemperatureFahrenheit), Nothing), TemperatureFahrenheit)
Console.WriteLine("{0} equals {1}.", tempC1, tempF1) 
Dim tempC2 As TemperatureCelsius = CType(Convert.ChangeType(tempC1, GetType(TemperatureCelsius), Nothing), TemperatureCelsius)
Console.WriteLine("{0} equals {1}.", tempC1, tempC2) 
Dim tempF2 As New TemperatureFahrenheit(212)
Dim tempC3 As TEmperatureCelsius = CType(Convert.ChangeType(tempF2, GEtType(TemperatureCelsius), Nothing), TemperatureCelsius)
Console.WriteLine("{0} equals {1}.", tempF2, tempC3) 
Dim tempF3 As TemperatureFahrenheit = CType(Convert.ChangeType(tempF2, GetType(TemperatureFahrenheit), Nothing), TemperatureFahrenheit)
Console.WriteLine("{0} equals {1}.", tempF2, tempF3)
' The example displays the following output: 
'       0°C equals 32°F. 
'       0°C equals 0°C. 
'       212°F equals 100°C. 
'       212°F equals 212°F.