IConvertible Interface (System)

IConvertible Interface

.NET Framework 4

Defines methods that convert the value of the implementing reference or value type to a common language runtime type that has an equivalent value.

This API is not CLS-compliant.

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

Syntax

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'Declaration

<ComVisibleAttribute(True)> _
<CLSCompliantAttribute(False)> _
Public Interface IConvertible

Remarks

This interface provides methods to convert the value of an instance of an implementing type to a common language runtime type that has an equivalent value. The common language runtime types are Boolean, SByte, Byte, Int16, UInt16, Int32, UInt32, Int64, UInt64, Single, Double, Decimal, DateTime, Char, and String.

If there is no meaningful conversion to a common language runtime type, then a particular interface method implementation throws InvalidCastException. For example, if this interface is implemented on a Boolean type, the implementation of the ToDateTime method throws an exception because there is no meaningful DateTime equivalent to a Boolean type.

The common language runtime typically exposes the IConvertible interface through the Convert class. The common language runtime also uses the IConvertible interface internally, in explicit interface implementations, to simplify the code used to support conversions in the Convert class and basic common language runtime types.

In addition to the IConvertible interface, the .NET Framework provides classes called type converters for converting user-defined data types to other data types. For more information, see the Generalized Type Conversion topic.

Notes to Implementers

If you implement the IConvertible interface, your implementation will be called automatically by the Convert.ChangeType method if the Object parameter is an instance of your implementing type and the Type parameter is a common language runtime type.

Most conversion methods have a parameter of type IFormatProvider that represents either the current culture (CultureInfo.CurrentCulture) or a specific culture. For the most part, the IConvertible implementations of the base types ignore this parameter. However, you can choose whether to use it in your code.

Examples

The following code sample demonstrates an implementation of IConvertible for a Complex number class, allowing it to be cast first as a Double and then calling the static Convert members on that Double.

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Public Class Complex : Implements IConvertible
   Private x, y As Double

   Public Sub New(ByVal x As Double, ByVal y As Double)
      Me.x = x
      Me.y = y
   End Sub

   Function GetDoubleValue() As Double
      Return Math.Sqrt((x * x + y * y))
   End Function

   ' The remaining code provides IConvertible method implementations.
   Public Function GetTypeCode() As TypeCode Implements IConvertible.GetTypeCode
      Return TypeCode.Object
   End Function

   Function ToBoolean(ByVal provider As IFormatProvider) As Boolean _
            Implements IConvertible.ToBoolean
      Return x <> 0 OrElse y <> 0
   End Function

   Function ToByte(ByVal provider As IFormatProvider) As Byte Implements IConvertible.ToByte
       Return Convert.ToByte(GetDoubleValue())
   End Function

   Function ToChar(ByVal provider As IFormatProvider) As Char Implements IConvertible.ToChar
      Return Convert.ToChar(GetDoubleValue())
   End Function

   Function ToDateTime(ByVal provider As IFormatProvider) As DateTime Implements IConvertible.ToDateTime
      Return Convert.ToDateTime(GetDoubleValue())
   End Function

   Function ToDecimal(ByVal provider As IFormatProvider) As Decimal Implements IConvertible.ToDecimal
      Return Convert.ToDecimal(GetDoubleValue())
   End Function

   Function ToDouble(ByVal provider As IFormatProvider) As Double Implements IConvertible.ToDouble
      Return GetDoubleValue()
   End Function

   Function ToInt16(ByVal provider As IFormatProvider) As Short Implements IConvertible.ToInt16
      Return Convert.ToInt16(GetDoubleValue())
   End Function

   Function ToInt32(ByVal provider As IFormatProvider) As Integer Implements IConvertible.ToInt32
      Return Convert.ToInt32(GetDoubleValue())
   End Function

   Function ToInt64(ByVal provider As IFormatProvider) As Long Implements IConvertible.ToInt64
      Return Convert.ToInt64(GetDoubleValue())
   End Function

   Function ToSByte(ByVal provider As IFormatProvider) As SByte Implements IConvertible.ToSByte
      Return Convert.ToSByte(GetDoubleValue())
   End Function

   Function ToSingle(ByVal provider As IFormatProvider) As Single Implements IConvertible.ToSingle
      Return Convert.ToSingle(GetDoubleValue())
   End Function

   Overloads Function ToString(ByVal provider As IFormatProvider) As String Implements IConvertible.ToString
      Return String.Format("({0}, {1})", x, y)
   End Function

   Function ToType(ByVal conversionType As Type, ByVal provider As IFormatProvider) As Object Implements IConvertible.ToType
      Return Convert.ChangeType(GetDoubleValue(), conversionType)
   End Function

   Function ToUInt16(ByVal provider As IFormatProvider) As UInt16 Implements IConvertible.ToUInt16
      Return Convert.ToUInt16(GetDoubleValue())
   End Function

   Function ToUInt32(ByVal provider As IFormatProvider) As UInt32 Implements IConvertible.ToUInt32
      Return Convert.ToUInt32(GetDoubleValue())
   End Function

   Function ToUInt64(ByVal provider As IFormatProvider) As UInt64 Implements IConvertible.ToUInt64
      Return Convert.ToUInt64(GetDoubleValue())
   End Function
End Class

Public Module Example
   Sub Main()
      Dim testComplex As New Complex(4, 7)

      WriteObjectInfo(testComplex)
      WriteObjectInfo(Convert.ToBoolean(testComplex))
      WriteObjectInfo(Convert.ToDecimal(testComplex))
      WriteObjectInfo(Convert.ToString(testComplex))
   End Sub

   Sub WriteObjectInfo(ByVal testObject As Object)
      Dim typeCode As TypeCode = Type.GetTypeCode(testObject.GetType())

      Select Case typeCode
         Case typeCode.Boolean
            Console.WriteLine("Boolean: {0}", testObject)

         Case typeCode.Double
            Console.WriteLine("Double: {0}", testObject)

         Case Else
            Console.WriteLine("{0}: {1}", typeCode.ToString(), testObject)
      End Select
   End Sub
End Module

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role not supported), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Reference

IConvertible Members

System Namespace

Other Resources

Type Conversion in the .NET Framework

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