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Double.ToString Method (String)

Converts the numeric value of this instance to its equivalent string representation, using the specified format.

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

'Declaration
Public Function ToString ( _
	format As String _
) As String

Parameters

format
Type: System.String

A numeric format string.

Return Value

Type: System.String
The string representation of the value of this instance as specified by format.

ExceptionCondition
FormatException

format is invalid.

The ToString(String) method formats a Double value in a specified format by using the conventions of the current culture. If you want to specify a different format or culture, use the other overloads of the ToString method, as follows:

To use format

For culture

Use the overload

Default ("G") format

Default (current) culture

ToString

Default ("G") format

A specific culture

ToString(IFormatProvider)

A specific format or precision

A specific culture

ToString(String, IFormatProvider)

The return value can be PositiveInfinitySymbol, NegativeInfinitySymbol, NaNSymbol, or the string representation of a number, as specified by format.

The format parameter can be any valid standard numeric format specifier except for D and X, as well as any combination of custom numeric format specifiers. If format is Nothing or an empty string, the return value is formatted with the general numeric format specifier ("G").

The .NET Framework provides extensive formatting support, which is described in greater detail in the following formatting topics:

By default, the return value only contains 15 digits of precision although a maximum of 17 digits is maintained internally. If the value of this instance has greater than 15 digits, ToString returns PositiveInfinitySymbol or NegativeInfinitySymbol instead of the expected number. If you require more precision, specify format with the "G17" format specification, which always returns 17 digits of precision, or "R", which returns 15 digits if the number can be represented with that precision or 17 digits if the number can only be represented with maximum precision.

Notes to Callers

In some cases, Double values formatted with the "R" standard numeric format string do not successfully round-trip if compiled using the /platform:x64 or /platform:anycpu switches and run on 64-bit systems. To work around this problem, you can format Double values by using the "G17" standard numeric format string. The following example uses the "R" format string with a Double value that does not round-trip successfully, and also uses the "G17" format string to successfully round-trip the original value.

Module Example
   Public Sub Main()
      Console.WriteLine("Attempting to round-trip a Double with 'R':")
      Dim initialValue As Double = 0.6822871999174
      Dim valueString As String = initialValue.ToString("R")
      Dim roundTripped As Double = Double.Parse(valueString)
      Console.WriteLine("{0:R} = {1:R}: {2}",
                        initialValue, roundTripped, initialValue.Equals(roundTripped))
      Console.WriteLine()

      Console.WriteLine("Attempting to round-trip a Double with 'G17':")
      Dim valueString17 As String = initialValue.ToString("G17")
      Dim roundTripped17 As Double = Double.Parse(valueString17)
      Console.WriteLine("{0:R} = {1:R}: {2}",
                        initialValue, roundTripped17, initialValue.Equals(roundTripped17))
   End Sub 
End Module 
' If compiled to an application that targets anycpu or x64 and run on an x64 system, 
' the example displays the following output: 
'       Attempting to round-trip a Double with 'R': 
'       0.6822871999174 = 0.68228719991740006: False 

'       Attempting to round-trip a Double with 'G17': 
'       0.6822871999174 = 0.6822871999174: True

The following example displays several Double values using the supported standard numeric format specifiers together with three custom numeric format strings. One of those custom format strings illustrates how to pad a Single value with leading zeros. In addition, the example uses precision specifiers with each standard format specifier except for "R". The values of the precision specifiers range from 0 to 3. To convert the numeric values to strings, the example uses the formatting conventions of the en-US culture.

Dim numbers() As Double = {1054.32179, -195489100.8377, 1.0437E21, _
                         -1.0573e-05}
Dim specifiers() As String = { "C", "E", "e", "F", "G", "N", "P", _
                               "R", "#,000.000", "0.###E-000", _
                               "000,000,000,000.00###" }
For Each number As Double In numbers
   Console.WriteLine("Formatting of {0}:", number)
   For Each specifier As String In specifiers
      Console.WriteLine("   {0,-22} {1}", 
                        specifier + ":", number.ToString(specifier))
      ' Add precision specifiers from 0 to 3. 
      If specifier.Length = 1 And Not specifier.Equals("R") Then 
         For precision As Integer = 0 To 3
            Dim pSpecifier As String = String.Format("{0}{1}", specifier, precision)
            Console.WriteLine("   {0,-22} {1}", 
                              pSpecifier + ":", number.ToString(pSpecifier))
         Next
         Console.WriteLine()      
      End If 
   Next
   Console.WriteLine()
Next 
' The example displays the following output: 
'       Formatting of 1054.32179: 
'          C:                     $1,054.32 
'          C0:                    $1,054 
'          C1:                    $1,054.3 
'          C2:                    $1,054.32 
'          C3:                    $1,054.322 
'        
'          E:                     1.054322E+003 
'          E0:                    1E+003 
'          E1:                    1.1E+003 
'          E2:                    1.05E+003 
'          E3:                    1.054E+003 
'        
'          e:                     1.054322e+003 
'          e0:                    1e+003 
'          e1:                    1.1e+003 
'          e2:                    1.05e+003 
'          e3:                    1.054e+003 
'        
'          F:                     1054.32 
'          F0:                    1054 
'          F1:                    1054.3 
'          F2:                    1054.32 
'          F3:                    1054.322 
'        
'          G:                     1054.32179 
'          G0:                    1054.32179 
'          G1:                    1E+03 
'          G2:                    1.1E+03 
'          G3:                    1.05E+03 
'        
'          N:                     1,054.32 
'          N0:                    1,054 
'          N1:                    1,054.3 
'          N2:                    1,054.32 
'          N3:                    1,054.322 
'        
'          P:                     105,432.18 % 
'          P0:                    105,432 % 
'          P1:                    105,432.2 % 
'          P2:                    105,432.18 % 
'          P3:                    105,432.179 % 
'        
'          R:                     1054.32179 
'          #,000.000:             1,054.322 
'          0.###E-000:            1.054E003 
'          000,000,000,000.00###: 000,000,001,054.32179 
'        
'       Formatting of -195489100.8377: 
'          C:                     ($195,489,100.84) 
'          C0:                    ($195,489,101) 
'          C1:                    ($195,489,100.8) 
'          C2:                    ($195,489,100.84) 
'          C3:                    ($195,489,100.838) 
'        
'          E:                     -1.954891E+008 
'          E0:                    -2E+008 
'          E1:                    -2.0E+008 
'          E2:                    -1.95E+008 
'          E3:                    -1.955E+008 
'        
'          e:                     -1.954891e+008 
'          e0:                    -2e+008 
'          e1:                    -2.0e+008 
'          e2:                    -1.95e+008 
'          e3:                    -1.955e+008 
'        
'          F:                     -195489100.84 
'          F0:                    -195489101 
'          F1:                    -195489100.8 
'          F2:                    -195489100.84 
'          F3:                    -195489100.838 
'        
'          G:                     -195489100.8377 
'          G0:                    -195489100.8377 
'          G1:                    -2E+08 
'          G2:                    -2E+08 
'          G3:                    -1.95E+08 
'        
'          N:                     -195,489,100.84 
'          N0:                    -195,489,101 
'          N1:                    -195,489,100.8 
'          N2:                    -195,489,100.84 
'          N3:                    -195,489,100.838 
'        
'          P:                     -19,548,910,083.77 % 
'          P0:                    -19,548,910,084 % 
'          P1:                    -19,548,910,083.8 % 
'          P2:                    -19,548,910,083.77 % 
'          P3:                    -19,548,910,083.770 % 
'        
'          R:                     -195489100.8377 
'          #,000.000:             -195,489,100.838 
'          0.###E-000:            -1.955E008 
'          000,000,000,000.00###: -000,195,489,100.8377 
'        
'       Formatting of 1.0437E+21: 
'          C:                     $1,043,700,000,000,000,000,000.00 
'          C0:                    $1,043,700,000,000,000,000,000 
'          C1:                    $1,043,700,000,000,000,000,000.0 
'          C2:                    $1,043,700,000,000,000,000,000.00 
'          C3:                    $1,043,700,000,000,000,000,000.000 
'        
'          E:                     1.043700E+021 
'          E0:                    1E+021 
'          E1:                    1.0E+021 
'          E2:                    1.04E+021 
'          E3:                    1.044E+021 
'        
'          e:                     1.043700e+021 
'          e0:                    1e+021 
'          e1:                    1.0e+021 
'          e2:                    1.04e+021 
'          e3:                    1.044e+021 
'        
'          F:                     1043700000000000000000.00 
'          F0:                    1043700000000000000000 
'          F1:                    1043700000000000000000.0 
'          F2:                    1043700000000000000000.00 
'          F3:                    1043700000000000000000.000 
'        
'          G:                     1.0437E+21 
'          G0:                    1.0437E+21 
'          G1:                    1E+21 
'          G2:                    1E+21 
'          G3:                    1.04E+21 
'        
'          N:                     1,043,700,000,000,000,000,000.00 
'          N0:                    1,043,700,000,000,000,000,000 
'          N1:                    1,043,700,000,000,000,000,000.0 
'          N2:                    1,043,700,000,000,000,000,000.00 
'          N3:                    1,043,700,000,000,000,000,000.000 
'        
'          P:                     104,370,000,000,000,000,000,000.00 % 
'          P0:                    104,370,000,000,000,000,000,000 % 
'          P1:                    104,370,000,000,000,000,000,000.0 % 
'          P2:                    104,370,000,000,000,000,000,000.00 % 
'          P3:                    104,370,000,000,000,000,000,000.000 % 
'        
'          R:                     1.0437E+21 
'          #,000.000:             1,043,700,000,000,000,000,000.000 
'          0.###E-000:            1.044E021 
'          000,000,000,000.00###: 1,043,700,000,000,000,000,000.00 
'        
'       Formatting of -1.0573E-05: 
'          C:                     $0.00 
'          C0:                    $0 
'          C1:                    $0.0 
'          C2:                    $0.00 
'          C3:                    $0.000 
'        
'          E:                     -1.057300E-005 
'          E0:                    -1E-005 
'          E1:                    -1.1E-005 
'          E2:                    -1.06E-005 
'          E3:                    -1.057E-005 
'        
'          e:                     -1.057300e-005 
'          e0:                    -1e-005 
'          e1:                    -1.1e-005 
'          e2:                    -1.06e-005 
'          e3:                    -1.057e-005 
'        
'          F:                     0.00 
'          F0:                    0 
'          F1:                    0.0 
'          F2:                    0.00 
'          F3:                    0.000 
'        
'          G:                     -1.0573E-05 
'          G0:                    -1.0573E-05 
'          G1:                    -1E-05 
'          G2:                    -1.1E-05 
'          G3:                    -1.06E-05 
'        
'          N:                     0.00 
'          N0:                    0 
'          N1:                    0.0 
'          N2:                    0.00 
'          N3:                    0.000 
'        
'          P:                     0.00 % 
'          P0:                    0 % 
'          P1:                    0.0 % 
'          P2:                    0.00 % 
'          P3:                    -0.001 % 
'        
'          R:                     -1.0573E-05 
'          #,000.000:             000.000 
'          0.###E-000:            -1.057E-005 
'          000,000,000,000.00###: -000,000,000,000.00001

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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