Convert.ToString Method (Object, IFormatProvider)

Parameters

• value
  Type: System.Object
  An Object or nulla null reference (Nothing in Visual Basic).

• provider
  Type: System.IFormatProvider
  An IFormatProvider interface implementation that supplies culture-specific formatting information.

Return Value

Type: System.String
The String representation of the value of value, or String.Empty if value is nulla null reference (Nothing in Visual Basic).

' Example of Convert.ToString( non-numeric types, IFormatProvider ).
Imports System.Globalization

' An instance of this class can be passed to methods that require 
' an IFormatProvider.
Public Class DummyProvider
   Implements IFormatProvider

   ' Normally, GetFormat returns an object of the requested type
   ' (usually itself) if it is able; otherwise, it returns Nothing. 
   Public Function GetFormat(ByVal argType As Type) As Object _
       Implements IFormatProvider.GetFormat

      ' Here, the type of argType is displayed, and GetFormat
      ' always returns Nothing.
      outputBlock.Text &= String.Format("{0,-40}", argType.ToString())
      Return Nothing

   End Function
End Class

Module Example

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Create an instance of the IFormatProvider.
      Dim provider As New DummyProvider()
      Dim converted As String

      ' Convert these values using DummyProvider.
      Dim Int32A As Integer = -252645135
      Dim DoubleA As Double = 61680.3855
      Dim ObjDouble As Object = CType(-98765.4321, Object)
      Dim DayTimeA As DateTime = _
                          New DateTime(2001, 9, 11, 13, 45, 0)

      Dim BoolA As Boolean = True
      Dim StringA As String = "Qwerty"
      Dim CharA As Char = "$"c
      Dim TSpanA As TimeSpan = New TimeSpan(0, 18, 0)
      Dim ObjOther As Object = CType(provider, Object)

      outputBlock.Text &= "This example of " & _
          "Convert.ToString( non-numeric, IFormatProvider ) " & _
          vbCrLf & "generates the following output. The " & _
          "provider type, argument type, " & vbCrLf & "and " & _
          "argument value are displayed." & vbCrLf
      outputBlock.Text &= vbCrLf & _
          "Note: The IFormatProvider object is not called for " & _
          "Boolean, String, " & vbCrLf & "Char, TimeSpan, " & _
          "and non-numeric Object." & vbCrLf

      ' The format provider is called for these conversions.
      outputBlock.Text &= vbCrLf
      converted = Convert.ToString(Int32A, provider)
      outputBlock.Text &= String.Format("Int32    {0}", converted) & vbCrLf
      converted = Convert.ToString(DoubleA, provider)
      outputBlock.Text &= String.Format("Double   {0}", converted) & vbCrLf
      converted = Convert.ToString(ObjDouble, provider)
      outputBlock.Text &= String.Format("Object   {0}", converted) & vbCrLf
      converted = Convert.ToString(DayTimeA, provider)
      outputBlock.Text &= String.Format("DateTime {0}", converted) & vbCrLf

      ' The format provider is not called for these conversions.
      outputBlock.Text &= vbCrLf
      converted = Convert.ToString(BoolA, provider)
      outputBlock.Text &= String.Format("Boolean  {0}", converted) & vbCrLf
      converted = Convert.ToString(StringA, provider)
      outputBlock.Text &= String.Format("String   {0}", converted) & vbCrLf
      converted = Convert.ToString(CharA, provider)
      outputBlock.Text &= String.Format("Char     {0}", converted) & vbCrLf
      converted = Convert.ToString(TSpanA, provider)
      outputBlock.Text &= String.Format("TimeSpan {0}", converted) & vbCrLf
      converted = Convert.ToString(ObjOther, provider)
      outputBlock.Text &= String.Format("Object   {0}", converted) & vbCrLf

   End Sub
End Module

' This example of Convert.ToString( non-numeric, IFormatProvider )
' generates the following output. The provider type, argument type,
' and argument value are displayed.
'
' Note: The IFormatProvider object is not called for Boolean, String,
' Char, TimeSpan, and non-numeric Object.
' 
' System.Globalization.NumberFormatInfo   Int32    -252645135
' System.Globalization.NumberFormatInfo   Double   61680.3855
' System.Globalization.NumberFormatInfo   Object   -98765.4321
' System.Globalization.DateTimeFormatInfo DateTime 9/11/2001 1:45:00 PM
' 
' Boolean  True
' String   Qwerty
' Char     $
' TimeSpan 00:18:00
' Object   DummyProvider

// Example of Convert.ToString( non-numeric types, IFormatProvider ).
using System;
using System.Globalization;

// An instance of this class can be passed to methods that require 
// an IFormatProvider.
public class DummyProvider : IFormatProvider
{
   // Normally, GetFormat returns an object of the requested type
   // (usually itself) if it is able; otherwise, it returns Nothing. 
   public object GetFormat(Type argType)
   {
      // Here, the type of argType is displayed, and GetFormat
      // always returns Nothing.
      outputBlock.Text += String.Format("{0,-40}", argType.ToString());
      return null;
   }
}

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create an instance of the IFormatProvider.
      DummyProvider provider = new DummyProvider();
      string converted;

      // Convert these values using DummyProvider.
      int Int32A = -252645135;
      double DoubleA = 61680.3855;
      object ObjDouble = (object)(-98765.4321);
      DateTime DayTimeA = new DateTime(2001, 9, 11, 13, 45, 0);

      bool BoolA = true;
      string StringA = "Qwerty";
      char CharA = '$';
      TimeSpan TSpanA = new TimeSpan(0, 18, 0);
      object ObjOther = (object)provider;

      outputBlock.Text += "This example of " +
          "Convert.ToString( non-numeric, IFormatProvider ) \n" +
          "generates the following output. The provider type, " +
          "argument type, \nand argument value are displayed." + "\n";
      outputBlock.Text += "\nNote: The IFormatProvider object is " +
          "not called for Boolean, String, \nChar, TimeSpan, " +
          "and non-numeric Object." + "\n";

      // The format provider is called for these conversions.
      outputBlock.Text += "\n";
      converted = Convert.ToString(Int32A, provider);
      outputBlock.Text += String.Format("int      {0}", converted) + "\n";
      converted = Convert.ToString(DoubleA, provider);
      outputBlock.Text += String.Format("double   {0}", converted) + "\n";
      converted = Convert.ToString(ObjDouble, provider);
      outputBlock.Text += String.Format("object   {0}", converted) + "\n";
      converted = Convert.ToString(DayTimeA, provider);
      outputBlock.Text += String.Format("DateTime {0}", converted) + "\n";

      // The format provider is not called for these conversions.
      outputBlock.Text += "\n";
      converted = Convert.ToString(BoolA, provider);
      outputBlock.Text += String.Format("bool     {0}", converted) + "\n";
      converted = Convert.ToString(StringA, provider);
      outputBlock.Text += String.Format("string   {0}", converted) + "\n";
      converted = Convert.ToString(CharA, provider);
      outputBlock.Text += String.Format("char     {0}", converted) + "\n";
      converted = Convert.ToString(TSpanA, provider);
      outputBlock.Text += String.Format("TimeSpan {0}", converted) + "\n";
      converted = Convert.ToString(ObjOther, provider);
      outputBlock.Text += String.Format("object   {0}", converted) + "\n";
   }
}

/*
This example of Convert.ToString( non-numeric, IFormatProvider )
generates the following output. The provider type, argument type,
and argument value are displayed.

Note: The IFormatProvider object is not called for Boolean, String,
Char, TimeSpan, and non-numeric Object.

System.Globalization.NumberFormatInfo   int      -252645135
System.Globalization.NumberFormatInfo   double   61680.3855
System.Globalization.NumberFormatInfo   object   -98765.4321
System.Globalization.DateTimeFormatInfo DateTime 9/11/2001 1:45:00 PM

bool     True
string   Qwerty
char     $
TimeSpan 00:18:00
object   DummyProvider

*/