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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)

[ComVisibleAttribute(true)] 
[CLSCompliantAttribute(false)] 
public interface IConvertible
/** @attribute ComVisibleAttribute(true) */ 
/** @attribute CLSCompliantAttribute(false) */ 
public interface IConvertible
ComVisibleAttribute(true) 
CLSCompliantAttribute(false) 
public interface IConvertible

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.

using System;

namespace ConsoleApplication2
{

	/// Class that implements IConvertible
	class Complex : IConvertible
	{
		double	x;
		double	y;

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

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

		bool IConvertible.ToBoolean(IFormatProvider provider)
		{
			if(	(x != 0.0) || (y != 0.0) )
				return true;
			else
				return false;
		}

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

		byte IConvertible.ToByte(IFormatProvider provider)
		{
			return Convert.ToByte(GetDoubleValue());
		}

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

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

		decimal IConvertible.ToDecimal(IFormatProvider provider)
		{
			return Convert.ToDecimal(GetDoubleValue());
		}

		double IConvertible.ToDouble(IFormatProvider provider)
		{
			return GetDoubleValue();
		}

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

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

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

		sbyte IConvertible.ToSByte(IFormatProvider provider)
		{
			return Convert.ToSByte(GetDoubleValue());
		}

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

		string IConvertible.ToString(IFormatProvider provider)
		{
			return "( " + x.ToString() + " , " + y.ToString() + " )";
		}

		object IConvertible.ToType(Type conversionType, IFormatProvider provider)
		{
			return Convert.ChangeType(GetDoubleValue(),conversionType);
		}

		ushort IConvertible.ToUInt16(IFormatProvider provider)
		{
			return Convert.ToUInt16(GetDoubleValue());
		}

		uint IConvertible.ToUInt32(IFormatProvider provider)
		{
			return Convert.ToUInt32(GetDoubleValue());
		}

		ulong IConvertible.ToUInt64(IFormatProvider provider)
		{
			return Convert.ToUInt64(GetDoubleValue());
		}

	}

	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		static void Main(string[] args)
		{

			Complex		testComplex = new Complex(4,7);

			WriteObjectInfo(testComplex);
			WriteObjectInfo(Convert.ToBoolean(testComplex));
			WriteObjectInfo(Convert.ToDecimal(testComplex));
			WriteObjectInfo(Convert.ToString(testComplex));

		}

		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;
			}
		}
	}
}

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
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