Convert.ToDecimal Method (Object, IFormatProvider)

 
System_CAPS_noteNote

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Converts the value of the specified object to an equivalent decimal number, using the specified culture-specific formatting information.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

Public Shared Function ToDecimal (
	value As Object,
	provider As IFormatProvider
) As Decimal

Parameters

value
Type: System.Object

An object that implements the IConvertible interface.

provider
Type: System.IFormatProvider

An object that supplies culture-specific formatting information.

Return Value

Type: System.Decimal

A decimal number that is equivalent to value, or 0 (zero) if value is null.

Exception Condition
FormatException

value is not in an appropriate format for a Decimal type.

InvalidCastException

value does not implement the IConvertible interface.

-or-

The conversion is not supported.

OverflowException

value represents a number that is less than Decimal.MinValue or greater than Decimal.MaxValue.

The return value is the result of invoking the IConvertible.ToDecimal method of the underlying type of value.

provider enables the user to specify culture-specific conversion information about the contents of value. The base types ignore provider; however, the parameter may be used if value is a user-defined type that implements the IConvertible interface.

The following example defines a Temperature class that implements the IConvertible interface.

Imports System.Globalization

Public Class Temperature : Implements IConvertible
   Private m_Temp As Decimal

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

   Public ReadOnly Property Celsius() As Decimal
      Get
         Return Me.m_Temp
      End Get   
   End Property

   Public ReadOnly Property Kelvin() As Decimal
      Get
         Return Me.m_Temp + 273.15d   
      End Get
   End Property

   Public ReadOnly Property Fahrenheit() As Decimal
      Get
         Return Math.Round(CDec(Me.m_Temp * 9 / 5 + 32), 2)
      End Get      
   End Property

   Public Overrides Function ToString() As String
      Return m_Temp.ToString("N2") & " °C"
   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
      If m_Temp = 0 Then
         Return False
      Else
         Return True
      End If
   End Function 

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

   Public Function ToDouble(provider As IFormatProvider) As Double _
                   Implements IConvertible.ToDouble
      Return Decimal.ToDouble(Me.m_Temp)
   End Function   

   Public Function ToInt16(provider As IFormatProvider) As Int16 _
                   Implements IConvertible.ToInt16
      If Me.m_Temp < Int16.MinValue Or Me.m_Temp > Int16.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int16 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt16(Me.m_Temp)   
      End If
   End Function

   Public Function ToInt32(provider As IFormatProvider) As Int32 _
                   Implements IConvertible.ToInt32
      If Me.m_Temp < Int32.MinValue Or Me.m_Temp > Int32.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int32 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt32(Me.m_Temp)
      End If      
   End Function

   Public Function ToInt64(provider As IFormatProvider) As Int64 _
                   Implements IConvertible.ToInt64
      If Me.m_Temp < Int64.MinValue Or Me.m_Temp > Int64.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the Int64 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToInt64(Me.m_Temp)
      End If      
   End Function

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

   Public Function ToSingle(provider As IFormatProvider) As Single _
                   Implements IConvertible.ToSingle
      Return Decimal.ToSingle(Me.m_Temp)
   End Function

   Public Overloads Function ToString(provider As IFormatProvider) As String _
                   Implements IConvertible.ToString
      Return m_Temp.ToString("N2", provider) & " °C"
   End Function

   Public Function ToType(conversionType As Type, provider As IFormatProvider) As Object _
                   Implements IConvertible.ToType
      Select Case Type.GetTypeCode(conversionType)
         Case TypeCode.Boolean 
            Return Me.ToBoolean(Nothing)
         Case TypeCode.Byte
            Return Me.ToByte(Nothing)
         Case TypeCode.Char
            Return Me.ToChar(Nothing)
         Case TypeCode.DateTime
            Return Me.ToDateTime(Nothing)
         Case TypeCode.Decimal
            Return Me.ToDecimal(Nothing)
         Case TypeCode.Double
            Return Me.ToDouble(Nothing)
         Case TypeCode.Int16
            Return Me.ToInt16(Nothing)
         Case TypeCode.Int32
            Return Me.ToInt32(Nothing)
         Case TypeCode.Int64
            Return Me.ToInt64(Nothing)
         Case TypeCode.Object
            If GetType(Temperature).Equals(conversionType) Then
               Return Me
            Else
               Throw New InvalidCastException(String.Format("Conversion to a {0} is not supported.", _
                                                            conversionType.Name))
            End If 
         Case TypeCode.SByte
            Return Me.ToSByte(Nothing)
         Case TypeCode.Single
            Return Me.ToSingle(Nothing)
         Case TypeCode.String
            Return Me.ToString(provider)
         Case TypeCode.UInt16
            Return Me.ToUInt16(Nothing)
         Case TypeCode.UInt32
            Return Me.ToUInt32(Nothing)
         Case TypeCode.UInt64
            Return Me.ToUInt64(Nothing)   
         Case Else
            Throw New InvalidCastException(String.Format("Conversion to {0} is not supported.", conversionType.Name))   
      End Select
   End Function

   Public Function ToUInt16(provider As IFormatProvider) As UInt16 _
                   Implements IConvertible.ToUInt16
      If Me.m_Temp < UInt16.MinValue Or Me.m_Temp > UInt16.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt16 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt16(Me.m_Temp)
      End If   
   End Function

   Public Function ToUInt32(provider As IFormatProvider) As UInt32 _
                   Implements IConvertible.ToUInt32
      If Me.m_Temp < UInt32.MinValue Or Me.m_Temp > UInt32.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt32 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt32(Me.m_Temp)
      End If   
   End Function

   Public Function ToUInt64(provider As IFormatProvider) As UInt64 _
                   Implements IConvertible.ToUInt64
      If Me.m_Temp < UInt64.MinValue Or Me.m_Temp > UInt64.MaxValue Then
         Throw New OverflowException(String.Format("{0} is out of range of the UInt64 type.", _
                                                   Me.m_Temp))
      Else
         Return Decimal.ToUInt64(Me.m_temp)
      End If   
   End Function
End Class

The following example shows that when a Temperature object is passed as a parameter to the ToDecimal(Object, IFormatProvider) method, the IConvertible.ToDecimal implementation of the Temperature class is called to perform the conversion.

Module Example
   Public Sub Main()
      Dim cold As New Temperature(-40)
      Dim freezing As New Temperature(0)
      Dim boiling As New Temperature(100)

      Console.WriteLine(Convert.ToDecimal(cold, Nothing))
      Console.WriteLine(Convert.ToDecimal(freezing, Nothing))
      Console.WriteLine(Convert.ToDecimal(boiling, Nothing))
   End Sub
End Module
' The example displays the following output:
'       -40
'       0
'       100

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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