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IConvertible Interface

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

 

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

'Declaration
<ComVisibleAttribute(True)> _
<CLSCompliantAttribute(False)> _
Public Interface IConvertible
'Usage
Dim instance As IConvertible

/** @attribute ComVisibleAttribute(true) */ 
/** @attribute CLSCompliantAttribute(false) */ 
public interface IConvertible
ComVisibleAttribute(true) 
CLSCompliantAttribute(false) 
public interface IConvertible
Not applicable.

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.

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.

Imports System

Module Module1

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


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


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


        Function ToBoolean(ByVal provider As IFormatProvider) As Boolean Implements IConvertible.ToBoolean
            If x <> 0 Or y <> 0 Then
                Return True
            Else
                Return False
            End If
        End Function

        Function GetDoubleValue() As Double
            Return Math.Sqrt((x * x + y * y))
        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 "( " + x.ToString() + " , " + y.ToString() + " )"
        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


    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

package ConsoleApplication2 ;
import System.*;
/// Class that implements IConvertible
class Complex implements IConvertible
{
    private double x;
    private double y;

    public Complex(double x, double y)
    {
        this.x = x;
        this.y = y;
    } //Complex

    public TypeCode GetTypeCode()
    {
        return TypeCode.Object;
    } //GetTypeCode

    public boolean ToBoolean(IFormatProvider provider)
    {
        if (x != 0.0 || y != 0.0) {
            return true;
        }
        else {
            return false;
        }
    } //ToBoolean

    double GetDoubleValue()
    {
        return System.Math.Sqrt((x * x + y * y));
    } //GetDoubleValue

    public ubyte ToByte(IFormatProvider provider)
    {
        return Convert.ToByte(GetDoubleValue());
    } //ToByte

    public char ToChar(IFormatProvider provider)
    {
        return Convert.ToChar(GetDoubleValue());
    } //ToChar

    public DateTime ToDateTime(IFormatProvider provider)
    {
        return Convert.ToDateTime(GetDoubleValue());
    } //ToDateTime

    public System.Decimal ToDecimal(IFormatProvider provider)
    {
        return Convert.ToDecimal(GetDoubleValue());
    } //ToDecimal

    public double ToDouble(IFormatProvider provider)
    {
        return GetDoubleValue();
    } //ToDouble

    public short ToInt16(IFormatProvider provider)
    {
        return Convert.ToInt16(GetDoubleValue());
    } //ToInt16

    public int ToInt32(IFormatProvider provider)
    {
        return Convert.ToInt32(GetDoubleValue());
    } //ToInt32

    public long ToInt64(IFormatProvider provider)
    {
        return Convert.ToInt64(GetDoubleValue());
    } //ToInt64

    public byte ToSByte(IFormatProvider provider)
    {
        return Convert.ToSByte(GetDoubleValue());
    } //ToSByte

    public float ToSingle(IFormatProvider provider)
    {
        return Convert.ToSingle(GetDoubleValue());
    } //ToSingle

    public String ToString(IFormatProvider provider)
    {
        return "( " + System.Convert.ToString(x)
            + " , " + System.Convert.ToString(y)+ " )";
    } //ToString

    public Object ToType(Type conversionType, IFormatProvider provider)
    {
        return Convert.ChangeType(new Double(GetDoubleValue()),
            conversionType);
    } //ToType

    public UInt16 ToUInt16(IFormatProvider provider)
    {        
        return Convert.ToUInt16(GetDoubleValue());
    } //ToUInt16

    public UInt32 ToUInt32(IFormatProvider provider)
    {        
        return Convert.ToUInt32(GetDoubleValue());
    } //ToUInt32

    public UInt64 ToUInt64(IFormatProvider provider)
    {        
        return Convert.ToUInt64(GetDoubleValue());
    } //ToUInt64
} //Complex

/// <summary>
/// Summary description for Class1.
/// </summary>
class Class1
{
    public static void main(String[] args)
    {
        Complex testComplex = new Complex(4, 7);

        WriteObjectInfo(testComplex);
        WriteObjectInfo((System.Boolean)(Convert.ToBoolean(testComplex)));
        WriteObjectInfo(Convert.ToDecimal(testComplex));
        WriteObjectInfo(Convert.ToString(testComplex));
    } //main

    static void WriteObjectInfo(Object testObject)
    {
        TypeCode typeCode = Type.GetTypeCode(testObject.GetType());

        switch (typeCode) {
            case TypeCode.Boolean :
                Console.WriteLine("Boolean: {0}", testObject);
                break;
            case TypeCode.Double :
                Console.WriteLine("Double: {0}", testObject);
                break;
            default :
                Console.WriteLine("{0}: {1}", typeCode.ToString(), testObject);
                break;
        }
    } //WriteObjectInfo
} //Class1   

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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