IConvertible Interface

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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

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

[CLSCompliantAttribute(false)]
[ComVisibleAttribute(true)]
public interface IConvertible

The IConvertible type exposes the following members.

Methods

	Name	Description
	GetTypeCode	Returns the TypeCode for this instance.
	ToBoolean	Converts the value of this instance to an equivalent Boolean value using the specified culture-specific formatting information.
	ToByte	Converts the value of this instance to an equivalent 8-bit unsigned integer using the specified culture-specific formatting information.
	ToChar	Converts the value of this instance to an equivalent Unicode character using the specified culture-specific formatting information.
	ToDateTime	Converts the value of this instance to an equivalent DateTime using the specified culture-specific formatting information.
	ToDecimal	Converts the value of this instance to an equivalent Decimal number using the specified culture-specific formatting information.
	ToDouble	Converts the value of this instance to an equivalent double-precision floating-point number using the specified culture-specific formatting information.
	ToInt16	Converts the value of this instance to an equivalent 16-bit signed integer using the specified culture-specific formatting information.
	ToInt32	Converts the value of this instance to an equivalent 32-bit signed integer using the specified culture-specific formatting information.
	ToInt64	Converts the value of this instance to an equivalent 64-bit signed integer using the specified culture-specific formatting information.
	ToSByte	Converts the value of this instance to an equivalent 8-bit signed integer using the specified culture-specific formatting information.
	ToSingle	Converts the value of this instance to an equivalent single-precision floating-point number using the specified culture-specific formatting information.
	ToString	Converts the value of this instance to an equivalent String using the specified culture-specific formatting information.
	ToType	Converts the value of this instance to an Object of the specified Type that has an equivalent value, using the specified culture-specific formatting information.
	ToUInt16	Converts the value of this instance to an equivalent 16-bit unsigned integer using the specified culture-specific formatting information.
	ToUInt32	Converts the value of this instance to an equivalent 32-bit unsigned integer using the specified culture-specific formatting information.
	ToUInt64	Converts the value of this instance to an equivalent 64-bit unsigned integer using the specified culture-specific formatting information.

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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 allows you to define a custom type converter to convert user-defined data types to other data types. A type converter is a class derived from System.ComponentModel.TypeConverter. It is associated with the class for which it serves as a type converter by applying the System.ComponentModel.TypeConverterAttribute attribute to that class.

Notes to Implementers

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

Most IConvertible methods have a parameter of type IFormatProvider. This parameter commonly 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 example 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.

Module Example

   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, provider)
      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 Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim testComplex As New Complex(4, 7)

      WriteObjectInfo(outputBlock, testComplex)
      WriteObjectInfo(outputBlock, Convert.ToBoolean(testComplex))
      WriteObjectInfo(outputBlock, Convert.ToDecimal(testComplex))
      WriteObjectInfo(outputBlock, Convert.ToString(testComplex))

   End Sub

   Sub WriteObjectInfo(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal testObject As Object)
      Dim typeCode As TypeCode = Type.GetTypeCode(testObject.GetType())

      Select Case typeCode
         Case typeCode.Boolean
            outputBlock.Text += String.Format("Boolean: {0}", testObject) & vbCrLf

         Case typeCode.Double
            outputBlock.Text += String.Format("Double: {0}", testObject) & vbCrLf

         Case Else
            outputBlock.Text += String.Format("{0}: {1}", typeCode.ToString(), testObject) & vbCrLf
      End Select
   End Sub

End Module

using System;

/// 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, provider);
   }

   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 Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      Complex testComplex = new Complex(4, 7);

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

   }

   static void WriteObjectInfo(System.Windows.Controls.TextBlock outputBlock, object testObject)
   {
      TypeCode typeCode = Type.GetTypeCode(testObject.GetType());

      switch (typeCode)
      {
         case TypeCode.Boolean:
            outputBlock.Text += String.Format("Boolean: {0}", testObject) + "\n";
            break;

         case TypeCode.Double:
            outputBlock.Text += String.Format("Double: {0}", testObject) + "\n";
            break;

         default:
            outputBlock.Text += String.Format("{0}: {1}", typeCode.ToString(), testObject) + "\n";
            break;
      }
   }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

See Also

Reference

System Namespace