BigInteger.ToString Method (String, IFormatProvider)


Converts the numeric value of the current BigInteger object to its equivalent string representation by using the specified format and culture-specific format information.

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

public string ToString(
	string format,
	IFormatProvider provider


Type: System.String

A standard or custom numeric format string.

Type: System.IFormatProvider

An object that supplies culture-specific formatting information.

Return Value

Type: System.String

The string representation of the current BigInteger value as specified by the format and provider parameters.

Exception Condition

format is not a valid format string.

The ToString(String, IFormatProvider) method formats a BigInteger value in a specified format by using the NumberFormatInfo object of a specified culture. If you want to use the round-trip format or default culture settings, use the other overloads of the ToString method, as follows:

To use format

For culture

Use the overload

Round-trip ("R") format

Default (current) culture


Round-trip ("R") format

A specific culture


A specific format

Default (current) culture


The format parameter can be any valid standard numeric string, or any combination of custom numeric format strings. If format is equal to String.Empty or is null, the return value of the current BigInteger object is formatted with the round-trip format specifier ("R"). If format is any other value, the method throws a FormatException.

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

The provider parameter is an IFormatProvider implementation. Its GetFormat method returns a NumberFormatInfo object that provides culture-specific information about the format of the string returned by this method. When the ToString(String, IFormatProvider) method is invoked, it calls the provider parameter's GetFormat method and passes it a Type object that represents the NumberFormatInfo type. The GetFormat method then returns the NumberFormatInfo object that provides information for formatting the value parameter, such as the negative sign symbol, the group separator symbol, or the decimal point symbol. There are three ways to use the provider parameter to supply formatting information to the ToString(String, IFormatProvider) method:

  • You can pass a CultureInfo object that represents the culture that supplies formatting information. Its GetFormat method returns the NumberFormatInfo object that provides numeric formatting information for that culture.

  • You can pass the actual NumberFormatInfo object that provides numeric formatting information. (Its implementation of GetFormat just returns itself.)

  • You can pass a custom object that implements IFormatProvider. Its GetFormat method instantiates and returns the NumberFormatInfo object that provides formatting information.

If provider is null, the formatting of the returned string is based on the NumberFormatInfo object of the current culture.

The following example initializes a BigInteger value, and displays it to the console using a standard format string and a NumberFormatInfo object that defines the tilde (~) as a negative sign.

// Redefine the negative sign as the tilde for the invariant culture.
NumberFormatInfo bigIntegerFormatter = new NumberFormatInfo();
bigIntegerFormatter.NegativeSign = "~";

BigInteger value = BigInteger.Parse("-903145792771643190182");
string[] specifiers = { "C", "D", "D25", "E", "E4", "e8", "F0", 
                        "G", "N0", "P", "R", "X", "0,0.000", 
                        "#,#.00#;(#,#.00#)" };

foreach (string specifier in specifiers)
   Console.WriteLine("{0}: {1}", specifier, value.ToString(specifier, 

// The example displays the following output:
//    C: (☼903,145,792,771,643,190,182.00)
//    D: ~903145792771643190182
//    D25: ~0000903145792771643190182
//    E: ~9.031457E+020
//    E4: ~9.0314E+020
//    e8: ~9.03145792e+020
//    F0: ~903145792771643190182
//    G: ~903145792771643190182
//    N0: ~903,145,792,771,643,190,182
//    P: ~90,314,579,277,164,319,018,200.00 %
//    R: ~903145792771643190182
//    X: CF0A55968BB1A7545A
//    0,0.000: ~903,145,792,771,643,190,182.000
//    #,#.00#;(#,#.00#): (903,145,792,771,643,190,182.00)

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 4.0
Windows Phone
Available since 8.1
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