IConvertible Interface

Definition

public interface class IConvertible

[System.CLSCompliant(false)]
public interface IConvertible

[System.CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(true)]
public interface IConvertible

[<System.CLSCompliant(false)>]
type IConvertible = interface

[<System.CLSCompliant(false)>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type IConvertible = interface

Public Interface IConvertible

Derived

System.Boolean

System.Byte

System.Char

System.DateTime

System.DBNull

More…

Attributes

CLSCompliantAttribute ComVisibleAttribute

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.

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 String.Format("({0}, {1})", x, y);
 }

 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;
 }
 }
 }
}

open System

/// Class that implements IConvertible
type Complex(x, y) =
 member _.GetDoubleValue() =
 sqrt (x * x + y * y)
 
 interface IConvertible with
 member _.GetTypeCode() =
 TypeCode.Object

 member _.ToBoolean(provider: IFormatProvider) =
 (x <> 0.) || (y <> 0.)

 member this.ToByte(provider: IFormatProvider) =
 Convert.ToByte(this.GetDoubleValue())

 member this.ToChar(provider: IFormatProvider) =
 Convert.ToChar(this.GetDoubleValue())

 member this.ToDateTime(provider: IFormatProvider) =
 Convert.ToDateTime(this.GetDoubleValue())

 member this.ToDecimal(provider: IFormatProvider) =
 Convert.ToDecimal(this.GetDoubleValue())

 member this.ToDouble(provider: IFormatProvider) =
 this.GetDoubleValue()

 member this.ToInt16(provider: IFormatProvider) =
 Convert.ToInt16(this.GetDoubleValue())

 member this.ToInt32(provider: IFormatProvider) =
 Convert.ToInt32(this.GetDoubleValue())

 member this.ToInt64(provider: IFormatProvider) =
 Convert.ToInt64(this.GetDoubleValue())

 member this.ToSByte(provider: IFormatProvider) =
 Convert.ToSByte(this.GetDoubleValue())

 member this.ToSingle(provider: IFormatProvider) =
 Convert.ToSingle(this.GetDoubleValue())

 member _.ToString(provider: IFormatProvider) =
 $"({x}, {y})"

 member this.ToType(conversionType: Type, provider: IFormatProvider) =
 Convert.ChangeType(this.GetDoubleValue(), conversionType)

 member this.ToUInt16(provider: IFormatProvider) =
 Convert.ToUInt16(this.GetDoubleValue())

 member this.ToUInt32(provider: IFormatProvider) =
 Convert.ToUInt32(this.GetDoubleValue())

 member this.ToUInt64(provider: IFormatProvider) =
 Convert.ToUInt64(this.GetDoubleValue())

let writeObjectInfo testObject =
 let typeCode = Type.GetTypeCode(testObject.GetType())
 match typeCode with
 | TypeCode.Boolean ->
 printfn $"Boolean: {testObject}"
 | TypeCode.Double ->
 printfn $"Boolean: {testObject}"
 | _ ->
 printfn $"{typeCode}: {testObject}"

let testComplex = Complex(4, 7)

writeObjectInfo testComplex
writeObjectInfo (Convert.ToBoolean testComplex)
writeObjectInfo (Convert.ToDecimal testComplex)
writeObjectInfo (Convert.ToString testComplex)

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

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 ChangeType(Object, Type) 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 (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.

See also

• Type Conversion in the .NET Framework