BigInteger.Parse Method

Definition

Namespace:

System.Numerics

Assemblies:

netstandard.dll, System.Runtime.Numerics.dll

Converts the string representation of a number to its BigInteger equivalent.

Overloads

Parse(String)	Converts the string representation of a number to its BigInteger equivalent.
Parse(ReadOnlySpan<Char>, IFormatProvider)	Parses a span of characters into a value.
Parse(String, NumberStyles)	Converts the string representation of a number in a specified style to its BigInteger equivalent.
Parse(String, IFormatProvider)	Converts the string representation of a number in a specified culture-specific format to its BigInteger equivalent.
Parse(ReadOnlySpan<Char>, NumberStyles, IFormatProvider)	Converts the representation of a number, contained in the specified read-only span of characters, in a specified style to its BigInteger equivalent.
Parse(String, NumberStyles, IFormatProvider)	Converts the string representation of a number in a specified style and culture-specific format to its BigInteger equivalent.

Parse(String)

Source:

BigInteger.cs

Converts the string representation of a number to its BigInteger equivalent.

C#

public static System.Numerics.BigInteger Parse(string value);

Parameters

value

String

A string that contains the number to convert.

Returns

BigInteger

A value that is equivalent to the number specified in the value parameter.

Exceptions

ArgumentNullException

value is null.

FormatException

value is not in the correct format.

Examples

The following example uses the Parse(String) method to instantiate two BigInteger objects. It multiplies each object by another number and then calls the Compare method to determine the relationship between the two values.

C#

string stringToParse = String.Empty;
try
{
   // Parse two strings.
   string string1, string2;
   string1 = "12347534159895123";
   string2 = "987654321357159852";
   stringToParse = string1;
   BigInteger number1 = BigInteger.Parse(stringToParse);
   Console.WriteLine("Converted '{0}' to {1:N0}.", stringToParse, number1);
   stringToParse = string2;
   BigInteger number2 = BigInteger.Parse(stringToParse);
   Console.WriteLine("Converted '{0}' to {1:N0}.", stringToParse, number2);
   // Perform arithmetic operations on the two numbers.
   number1 *= 3;
   number2 *= 2;
   // Compare the numbers.
   int result = BigInteger.Compare(number1, number2);
   switch (result)
   {
      case -1:
         Console.WriteLine("{0} is greater than {1}.", number2, number1);
         break;
      case 0:
         Console.WriteLine("{0} is equal to {1}.", number1, number2);
         break;
      case 1:
         Console.WriteLine("{0} is greater than {1}.", number1, number2);
         break;
   }
}
catch (FormatException)
{
   Console.WriteLine("Unable to parse {0}.", stringToParse);
}
// The example displays the following output:
//    Converted '12347534159895123' to 12,347,534,159,895,123.
//    Converted '987654321357159852' to 987,654,321,357,159,852.
//    1975308642714319704 is greater than 37042602479685369.

Remarks

The value parameter should be the string representation of a number in the following form.

[ws][sign]digits[ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space.
sign	An optional sign. Valid sign characters are determined by the NumberFormatInfo.NegativeSign and NumberFormatInfo.PositiveSign properties of the current culture.
digits	A sequence of digits ranging from 0 to 9. Any leading zeros are ignored.

Note

The string specified by the value parameter is interpreted by using the NumberStyles.Integer style. It cannot contain any group separators or decimal separator, and it cannot have a decimal portion.

The value parameter is parsed by using the formatting information in a System.Globalization.NumberFormatInfo object that is initialized for the current system culture. For more information, see NumberFormatInfo.CurrentInfo. To parse a string by using the formatting information of a specific culture, use the Parse(String, IFormatProvider) method.

Important

If you use the Parse method to round-trip the string representation of a BigInteger value that was output by the ToString method, you should use the BigInteger.ToString(String) method with the "R" format specifier to generate the string representation of the BigInteger value. Otherwise, the string representation of the BigInteger preserves only the 50 most significant digits of the original value, and data may be lost when you use the Parse method to restore the BigInteger value.

See also

• TryParse

Parse(ReadOnlySpan<Char>, IFormatProvider)

Source:

BigInteger.cs

Parses a span of characters into a value.

C#

public static System.Numerics.BigInteger Parse(ReadOnlySpan<char> s, IFormatProvider? provider);

Parameters

s

ReadOnlySpan<Char>

The span of characters to parse.

provider

IFormatProvider

An object that provides culture-specific formatting information about s.

Returns

BigInteger

The result of parsing s.

Implements

Parse(ReadOnlySpan<Char>, IFormatProvider)

Parse(String, NumberStyles)

Source:

BigInteger.cs

Converts the string representation of a number in a specified style to its BigInteger equivalent.

C#

public static System.Numerics.BigInteger Parse(string value, System.Globalization.NumberStyles style);

Parameters

value

String

A string that contains a number to convert.

style

NumberStyles

A bitwise combination of the enumeration values that specify the permitted format of value.

Returns

BigInteger

A value that is equivalent to the number specified in the value parameter.

Exceptions

ArgumentException

style is not a NumberStyles value.

-or-

style includes the AllowHexSpecifier or HexNumber flag along with another value.

ArgumentNullException

value is null.

FormatException

value does not comply with the input pattern specified by NumberStyles.

Examples

The following example illustrates calls to the Parse(String, NumberStyles) method with several possible values for the style parameter. It illustrates how to interpret a string as a hexadecimal value, and how to disallow spaces and sign symbols.

C#

BigInteger number;
// Method should succeed (white space and sign allowed)
number = BigInteger.Parse("   -68054   ", NumberStyles.Integer);
Console.WriteLine(number);
// Method should succeed (string interpreted as hexadecimal)
number = BigInteger.Parse("68054", NumberStyles.AllowHexSpecifier);
Console.WriteLine(number);
// Method call should fail: sign not allowed
try
{
   number = BigInteger.Parse("   -68054  ", NumberStyles.AllowLeadingWhite
                                            | NumberStyles.AllowTrailingWhite);
   Console.WriteLine(number);
}
catch (FormatException e)
{
   Console.WriteLine(e.Message);
}
// Method call should fail: white space not allowed
try
{
   number = BigInteger.Parse("   68054  ", NumberStyles.AllowLeadingSign);
   Console.WriteLine(number);
}
catch (FormatException e)
{
   Console.WriteLine(e.Message);
}
//
// The method produces the following output:
//
//     -68054
//     426068
//     Input string was not in a correct format.
//     Input string was not in a correct format.

Remarks

The style parameter defines the style elements (such as white space, the positive or negative sign symbol, the group separator symbol, or the decimal point symbol) that are allowed in the value parameter for the parse operation to succeed. styles must be a combination of bit flags from the NumberStyles enumeration. The style parameter makes this method overload useful when value contains the string representation of a hexadecimal value, when the number system (decimal or hexadecimal) represented by value is known only at run time, or when you want to disallow white space or a sign symbol in value.

Depending on the value of style, the value parameter may include the following elements:

[ws][$][sign][digits,]digits[.fractional_digits][E[sign]exponential_digits][ws]

If style includes NumberStyles.AllowHexSpecifier, the value parameter may contain the following elements:

[ws]hexdigits[ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space. White space can appear at the start of value if style includes the NumberStyles.AllowLeadingWhite flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingWhite flag.
$	A culture-specific currency symbol. Its position in the string is defined by the NumberFormatInfo.CurrencyNegativePattern and NumberFormatInfo.CurrencyPositivePattern properties of the current culture. The current culture's currency symbol can appear in value if style includes the NumberStyles.AllowCurrencySymbol flag.
sign	An optional sign. The sign can appear at the start of value if style includes the NumberStyles.AllowLeadingSign flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingSign flag. Parentheses can be used in value to indicate a negative value if style includes the NumberStyles.AllowParentheses flag.
digits fractional_digits exponential_digits	A sequence of digits from 0 through 9. For fractional_digits, only the digit 0 is valid.
,	A culture-specific group separator symbol. The current culture's group separator can appear in value if style includes the NumberStyles.AllowThousands flag.
.	A culture-specific decimal point symbol. The current culture's decimal point symbol can appear in value if style includes the NumberStyles.AllowDecimalPoint flag. Only the digit 0 can appear as a fractional digit for the parse operation to succeed; if fractional_digits includes any other digit, a FormatException is thrown.
E	The "e" or "E" character, which indicates that the value is represented in exponential (scientific) notation. The value parameter can represent a number in exponential notation if style includes the NumberStyles.AllowExponent flag.
hexdigits	A sequence of hexadecimal digits from 0 through f, or 0 through F.

Note

Any terminating NUL (U+0000) characters in s are ignored by the parsing operation, regardless of the value of the style argument.

A string with digits only (which corresponds to the NumberStyles.None style) always parses successfully. Most of the remaining NumberStyles members control elements that may be present, but are not required to be present, in the input string. The following table indicates how individual NumberStyles members affect the elements that may be present in value.

NumberStyles value	Elements permitted in value in addition to digits
None	The digits element only.
AllowDecimalPoint	The decimal point (.) and fractional-digits elements.
AllowExponent	The "e" or "E" character, which indicates exponential notation, along with exponential_digits.
AllowLeadingWhite	The ws element at the start of value.
AllowTrailingWhite	The ws element at the end of value.
AllowLeadingSign	The sign element at the start of value.
AllowTrailingSign	The sign element at the end of value.
AllowParentheses	The sign element in the form of parentheses enclosing the numeric value.
AllowThousands	The group separator (,) element.
AllowCurrencySymbol	The currency ($) element.
Currency	All elements. However, value cannot represent a hexadecimal number or a number in exponential notation.
Float	The ws element at the start or end of value, sign at the start of value, and the decimal point (.) symbol. The value parameter can also use exponential notation.
Number	The ws, sign, group separator (,), and decimal point (.) elements.
Any	All elements. However, value cannot represent a hexadecimal number.

Important

If you use the Parse method to round-trip the string representation of a BigInteger value that was output by the ToString method, you should use the BigInteger.ToString(String) method with the "R" format specifier to generate the string representation of the BigInteger value. Otherwise, the string representation of the BigInteger preserves only the 50 most significant digits of the original value, and data may be lost when you use the Parse method to restore the BigInteger value.

Unlike the other NumberStyles values, which allow for, but do not require, the presence of particular style elements in value, the NumberStyles.AllowHexSpecifier style value means that the individual numeric characters in value are always interpreted as hexadecimal characters. Valid hexadecimal characters are 0-9, A-F, and a-f. The only other flags that can be combined with the style parameter are NumberStyles.AllowLeadingWhite and NumberStyles.AllowTrailingWhite. (The NumberStyles enumeration includes a composite number style, HexNumber, that includes both white-space flags.)

Note

If value is the string representation of a hexadecimal number, it cannot be preceded by any decoration (such as 0x or &h) that differentiates it as a hexadecimal number. This causes the conversion to fail.

If value is a hexadecimal string, the Parse(String, NumberStyles) method interprets value as a negative number stored by using two's complement representation if its first two hexadecimal digits are greater than or equal to 0x80. In other words, the method interprets the highest-order bit of the first byte in value as the sign bit. To make sure that a hexadecimal string is correctly interpreted as a positive number, the first digit in value must have a value of zero. For example, the method interprets 0x80 as a negative value, but it interprets either 0x080 or 0x0080 as a positive value. The following example illustrates the difference between hexadecimal strings that represent negative and positive values.

C#

using System;
using System.Globalization;
using System.Numerics;

public class Example
{
   public static void Main()
   {
      string[] hexStrings = { "80", "E293", "F9A2FF", "FFFFFFFF",
                              "080", "0E293", "0F9A2FF", "0FFFFFFFF",
                              "0080", "00E293", "00F9A2FF", "00FFFFFFFF" };
      foreach (string hexString in hexStrings)
      {
         BigInteger number = BigInteger.Parse(hexString, NumberStyles.AllowHexSpecifier);
         Console.WriteLine("Converted 0x{0} to {1}.", hexString, number);
      }
   }
}
// The example displays the following output:
//       Converted 0x80 to -128.
//       Converted 0xE293 to -7533.
//       Converted 0xF9A2FF to -417025.
//       Converted 0xFFFFFFFF to -1.
//       Converted 0x080 to 128.
//       Converted 0x0E293 to 58003.
//       Converted 0x0F9A2FF to 16360191.
//       Converted 0x0FFFFFFFF to 4294967295.
//       Converted 0x0080 to 128.
//       Converted 0x00E293 to 58003.
//       Converted 0x00F9A2FF to 16360191.
//       Converted 0x00FFFFFFFF to 4294967295.

The value parameter is parsed by using the formatting information in a NumberFormatInfo object that is initialized for the current system culture. To specify the culture whose formatting information is used for the parse operation, call the Parse(String, NumberStyles, IFormatProvider) overload.

See also

• TryParse

Parse(String, IFormatProvider)

Source:

BigInteger.cs

Converts the string representation of a number in a specified culture-specific format to its BigInteger equivalent.

C#

public static System.Numerics.BigInteger Parse(string value, IFormatProvider? provider);

Parameters

value

String

A string that contains a number to convert.

provider

IFormatProvider

An object that provides culture-specific formatting information about value.

Returns

BigInteger

A value that is equivalent to the number specified in the value parameter.

Implements

Parse(String, IFormatProvider)

Exceptions

ArgumentNullException

value is null.

FormatException

value is not in the correct format.

Examples

The following examples show two ways to define the tilde (~) as a negative sign for formatting BigInteger values. Note that to display the BigInteger values in the same format as the original strings, your code must call the BigInteger.ToString(IFormatProvider) method and pass it the NumberFormatInfo object that provides formatting information.

The first example defines a class that implements IFormatProvider and uses the GetFormat method to return the NumberFormatInfo object that provides formatting information.

C#

public class BigIntegerFormatProvider : IFormatProvider
{
   public object GetFormat(Type formatType)
   {
      if (formatType == typeof(NumberFormatInfo))
      {
         NumberFormatInfo numberFormat = new NumberFormatInfo();
         numberFormat.NegativeSign = "~";
         return numberFormat;
      }
      else
      {
         return null;
      }
   }
}

A BigInteger object can then be instantiated with the following code:

C#

BigInteger number = BigInteger.Parse("~6354129876", new BigIntegerFormatProvider());
// Display value using same formatting information
Console.WriteLine(number.ToString(new BigIntegerFormatProvider()));
// Display value using formatting of current culture
Console.WriteLine(number);

The second example is more straightforward. It passes the NumberFormatInfo object that provides formatting information to the provider parameter.

C#

NumberFormatInfo fmt = new NumberFormatInfo();
fmt.NegativeSign = "~";

BigInteger number = BigInteger.Parse("~6354129876", fmt);
// Display value using same formatting information
Console.WriteLine(number.ToString(fmt));
// Display value using formatting of current culture
Console.WriteLine(number);

Remarks

The value parameter should be the string representation of a number in the following form:

[ws][sign]digits[ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space.
sign	An optional sign. Valid sign characters are determined by the NumberFormatInfo.NegativeSign and NumberFormatInfo.PositiveSign properties of the NumberFormatInfo object that is returned by the provider object's GetFormat method.
digits	A sequence of digits ranging from 0 to 9. Any leading zeros are ignored.

Note

The string specified by the value parameter is interpreted using the NumberStyles.Integer style. It cannot contain any group separators or decimal separator, and it cannot have a decimal portion.

Important

If you use the Parse method to round-trip the string representation of a BigInteger value that was output by the ToString method, you should use the BigInteger.ToString(String) method with the "R" format specifier to generate the string representation of the BigInteger value. Otherwise, the string representation of the BigInteger preserves only the 50 most significant digits of the original value, and data may be lost when you use the Parse method to restore the BigInteger value.

The provider parameter is an IFormatProvider implementation whose GetFormat method returns a NumberFormatInfo object that provides culture-specific formatting information. When the Parse(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 about the format of the value parameter. There are three ways to use the provider parameter to supply custom formatting information to the parse operation:

• 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 value is interpreted based on the NumberFormatInfo object of the current culture.

See also

• TryParse

Parse(ReadOnlySpan<Char>, NumberStyles, IFormatProvider)

Source:

BigInteger.cs

Converts the representation of a number, contained in the specified read-only span of characters, in a specified style to its BigInteger equivalent.

C#

public static System.Numerics.BigInteger Parse(ReadOnlySpan<char> value, System.Globalization.NumberStyles style = System.Globalization.NumberStyles.Integer, IFormatProvider? provider = default);

Parameters

value

ReadOnlySpan<Char>

A read-only span of characters that contains the number to convert.

style

NumberStyles

A bitwise combination of the enumeration values that specify the permitted format of value.

provider

IFormatProvider

An object that provides culture-specific formatting information about value.

Returns

BigInteger

A value that is equivalent to the number specified in the value parameter.

Implements

Parse(ReadOnlySpan<Char>, NumberStyles, IFormatProvider)

Exceptions

ArgumentException

style is not a NumberStyles value.

-or-

style includes the AllowHexSpecifier or HexNumber flag along with another value.

ArgumentNullException

value is null.

FormatException

value does not comply with the input pattern specified by style.

Remarks

The style parameter defines the style elements (such as white space, the positive or negative sign symbol, the group separator symbol, or the decimal point symbol) that are allowed in the value parameter for the parse operation to succeed. styles must be a combination of bit flags from the NumberStyles enumeration. The style parameter makes this method overload useful when value contains the representation of a hexadecimal value, when the number system (decimal or hexadecimal) represented by value is known only at run time, or when you want to disallow white space or a sign symbol in value.

Depending on the value of style, the value parameter may include the following elements:

[ws][$][sign][digits,]digits[.fractional_digits][E[sign]exponential_digits][ws]

If style includes NumberStyles.AllowHexSpecifier, the value parameter may include the following elements:

[ws]hexdigits[ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space. White space can appear at the start of value if style includes the NumberStyles.AllowLeadingWhite flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingWhite flag.
$	A culture-specific currency symbol. Its position in value is defined by the NumberFormatInfo.CurrencyNegativePattern and NumberFormatInfo.CurrencyPositivePattern properties of the culture indicated by the provider parameter. The current culture's currency symbol can appear in value if style includes the NumberStyles.AllowCurrencySymbol flag.
sign	An optional sign. The sign can appear at the start of value if style includes the NumberStyles.AllowLeadingSign flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingSign flag. Parentheses can be used in value to indicate a negative value if style includes the NumberStyles.AllowParentheses flag.
digits fractional_digits exponential_digits	A sequence of digits from 0 through 9. For fractional_digits, only the digit 0 is valid.
,	A culture-specific group separator symbol. The group separator symbol of the culture specified by provider can appear in value if style includes the NumberStyles.AllowThousands flag.
.	A culture-specific decimal point symbol. The decimal point symbol of the culture designated by provider can appear in value if style includes the NumberStyles.AllowDecimalPoint flag. Only the digit 0 can appear as a fractional digit for the parse operation to succeed; if fractional_digits includes any other digit, a FormatException is thrown.
E	The "e" or "E" character, which indicates that the value is represented in exponential (scientific) notation. The value parameter can represent a number in exponential notation if style includes the NumberStyles.AllowExponent flag.
hexdigits	A sequence of hexadecimal digits from 0 through f, or 0 through F.

Note

Any terminating NUL (U+0000) characters in s are ignored by the parsing operation, regardless of the value of the style argument.

A value with digits only (which corresponds to the NumberStyles.None style) always parses successfully. Most of the remaining NumberStyles members control elements that may be present, but are not required to be present, in value. The following table indicates how individual NumberStyles members affect the elements that may be present in value.

NumberStyles value	Elements permitted in value in addition to digits
None	The digits element only.
AllowDecimalPoint	The decimal point (.) and fractional-digits elements.
AllowExponent	The "e" or "E" character, which indicates exponential notation. along with exponential_digits.
AllowLeadingWhite	The ws element at the start of value.
AllowTrailingWhite	The ws element at the end of value.
AllowLeadingSign	The sign element at the start of value.
AllowTrailingSign	The sign element at the end of value.
AllowParentheses	The sign element in the form of parentheses enclosing the numeric value.
AllowThousands	The group separator (,) element.
AllowCurrencySymbol	The currency ($) element.
Currency	All elements. However, value cannot represent a hexadecimal number or a number in exponential notation.
Float	The ws element at the start or end of value, sign at the start of value, and the decimal point (.) symbol. The value parameter can also use exponential notation.
Number	The ws, sign, group separator (,), and decimal point (.) elements.
Any	All elements. However, value cannot represent a hexadecimal number.

Unlike the other NumberStyles values, which allow for but do not require the presence of particular style elements in value, the NumberStyles.AllowHexSpecifier style value means that the individual numeric characters in value are always interpreted as hexadecimal characters. Valid hexadecimal characters are 0-9, A-F, and a-f. The only other flags that can be combined with the style parameter are NumberStyles.AllowLeadingWhite and NumberStyles.AllowTrailingWhite. (The NumberStyles enumeration includes a composite number style, HexNumber, that includes both white-space flags.)

The provider parameter is an IFormatProvider implementation. Its GetFormat method returns a NumberFormatInfo object that provides culture-specific information about the format of value. Typically, provider can be any one of the following:

• A CultureInfo object that represents the culture that provides numeric formatting information. Its GetFormat method returns the NumberFormatInfo object that provides numeric formatting information.

• A NumberFormatInfo object that provides formatting information. (Its implementation of GetFormat just returns itself.)

• A custom object that implements IFormatProvider and uses the GetFormat method to instantiate and return the NumberFormatInfo object that provides formatting information.

If provider is null, the NumberFormatInfo object for the current culture is used.

See also

• TryParse

Parse(String, NumberStyles, IFormatProvider)

Source:

BigInteger.cs

Converts the string representation of a number in a specified style and culture-specific format to its BigInteger equivalent.

C#

public static System.Numerics.BigInteger Parse(string value, System.Globalization.NumberStyles style, IFormatProvider? provider);

Parameters

value

String

A string that contains a number to convert.

style

NumberStyles

A bitwise combination of the enumeration values that specify the permitted format of value.

provider

IFormatProvider

An object that provides culture-specific formatting information about value.

Returns

BigInteger

A value that is equivalent to the number specified in the value parameter.

Implements

Parse(String, NumberStyles, IFormatProvider)

Exceptions

ArgumentException

style is not a NumberStyles value.

-or-

style includes the AllowHexSpecifier or HexNumber flag along with another value.

ArgumentNullException

value is null.

FormatException

value does not comply with the input pattern specified by style.

Examples

The following example makes several calls to the Parse(String, NumberStyles, IFormatProvider) method using various combinations of values for the style and provider parameters.

C#

// Call parse with default values of style and provider
Console.WriteLine(BigInteger.Parse("  -300   ",
                  NumberStyles.Integer, CultureInfo.CurrentCulture));
// Call parse with default values of style and provider supporting tilde as negative sign
Console.WriteLine(BigInteger.Parse("   ~300  ",
                                   NumberStyles.Integer, new BigIntegerFormatProvider()));
// Call parse with only AllowLeadingWhite and AllowTrailingWhite
// Exception thrown because of presence of negative sign
try
{
   Console.WriteLine(BigInteger.Parse("    ~300   ",
                                NumberStyles.AllowLeadingWhite | NumberStyles.AllowTrailingWhite,
                                new BigIntegerFormatProvider()));
}
catch (FormatException e)
{
   Console.WriteLine("{0}: \n   {1}", e.GetType().Name, e.Message);
}
// Call parse with only AllowHexSpecifier
// Exception thrown because of presence of negative sign
try
{
   Console.WriteLine(BigInteger.Parse("-3af", NumberStyles.AllowHexSpecifier,
                                      new BigIntegerFormatProvider()));
}
catch (FormatException e)
{
   Console.WriteLine("{0}: \n   {1}", e.GetType().Name, e.Message);
}
// Call parse with only NumberStyles.None
// Exception thrown because of presence of white space and sign
try
{
   Console.WriteLine(BigInteger.Parse(" -300 ", NumberStyles.None,
                                      new BigIntegerFormatProvider()));
}
catch (FormatException e)
{
   Console.WriteLine("{0}: \n   {1}", e.GetType().Name, e.Message);
}
// The example displays the followingoutput:
//       -300
//       -300
//       FormatException:
//          The value could not be parsed.
//       FormatException:
//          The value could not be parsed.
//       FormatException:
//          The value could not be parsed.

A number of the individual calls to the Parse(String, NumberStyles, IFormatProvider) method pass an instance of the following BigIntegerFormatProvider class, which defines a tilde (~) as the negative sign.

C#

public class BigIntegerFormatProvider : IFormatProvider
{
   public object GetFormat(Type formatType)
   {
      if (formatType == typeof(NumberFormatInfo))
      {
         NumberFormatInfo numberFormat = new NumberFormatInfo();
         numberFormat.NegativeSign = "~";
         return numberFormat;
      }
      else
      {
         return null;
      }
   }
}

Remarks

The style parameter defines the style elements (such as white space, the positive or negative sign symbol, the group separator symbol, or the decimal point symbol) that are allowed in the value parameter for the parse operation to succeed. styles must be a combination of bit flags from the NumberStyles enumeration. The style parameter makes this method overload useful when value contains the string representation of a hexadecimal value, when the number system (decimal or hexadecimal) represented by value is known only at run time, or when you want to disallow white space or a sign symbol in value.

Depending on the value of style, the value parameter may include the following elements:

[ws][$][sign][digits,]digits[.fractional_digits][E[sign]exponential_digits][ws]

If style includes NumberStyles.AllowHexSpecifier, the value parameter may include the following elements:

[ws]hexdigits[ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space. White space can appear at the start of value if style includes the NumberStyles.AllowLeadingWhite flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingWhite flag.
$	A culture-specific currency symbol. Its position in the string is defined by the NumberFormatInfo.CurrencyNegativePattern and NumberFormatInfo.CurrencyPositivePattern properties of the culture indicated by the provider parameter. The current culture's currency symbol can appear in value if style includes the NumberStyles.AllowCurrencySymbol flag.
sign	An optional sign. The sign can appear at the start of value if style includes the NumberStyles.AllowLeadingSign flag, and it can appear at the end of value if style includes the NumberStyles.AllowTrailingSign flag. Parentheses can be used in value to indicate a negative value if style includes the NumberStyles.AllowParentheses flag.
digits fractional_digits exponential_digits	A sequence of digits from 0 through 9. For fractional_digits, only the digit 0 is valid.
,	A culture-specific group separator symbol. The group separator symbol of the culture specified by provider can appear in value if style includes the NumberStyles.AllowThousands flag.
.	A culture-specific decimal point symbol. The decimal point symbol of the culture designated by provider can appear in value if style includes the NumberStyles.AllowDecimalPoint flag. Only the digit 0 can appear as a fractional digit for the parse operation to succeed; if fractional_digits includes any other digit, a FormatException is thrown.
E	The "e" or "E" character, which indicates that the value is represented in exponential (scientific) notation. The value parameter can represent a number in exponential notation if style includes the NumberStyles.AllowExponent flag.
hexdigits	A sequence of hexadecimal digits from 0 through f, or 0 through F.

Note

Any terminating NUL (U+0000) characters in s are ignored by the parsing operation, regardless of the value of the style argument.

A string with digits only (which corresponds to the NumberStyles.None style) always parses successfully. Most of the remaining NumberStyles members control elements that may be present, but are not required to be present, in the input string. The following table indicates how individual NumberStyles members affect the elements that may be present in value.

NumberStyles value	Elements permitted in value in addition to digits
None	The digits element only.
AllowDecimalPoint	The decimal point (.) and fractional-digits elements.
AllowExponent	The "e" or "E" character, which indicates exponential notation. along with exponential_digits.
AllowLeadingWhite	The ws element at the start of value.
AllowTrailingWhite	The ws element at the end of value.
AllowLeadingSign	The sign element at the start of value.
AllowTrailingSign	The sign element at the end of value.
AllowParentheses	The sign element in the form of parentheses enclosing the numeric value.
AllowThousands	The group separator (,) element.
AllowCurrencySymbol	The currency ($) element.
Currency	All elements. However, value cannot represent a hexadecimal number or a number in exponential notation.
Float	The ws element at the start or end of value, sign at the start of value, and the decimal point (.) symbol. The value parameter can also use exponential notation.
Number	The ws, sign, group separator (,), and decimal point (.) elements.
Any	All elements. However, value cannot represent a hexadecimal number.

Important

If you use the Parse method to round-trip the string representation of a BigInteger value that was output by the ToString method, you should use the BigInteger.ToString(String) method with the "R" format specifier to generate the string representation of the BigInteger value. Otherwise, the string representation of the BigInteger preserves only the 50 most significant digits of the original value, and data may be lost when you use the Parse method to restore the BigInteger value.

Unlike the other NumberStyles values, which allow for but do not require the presence of particular style elements in value, the NumberStyles.AllowHexSpecifier style value means that the individual numeric characters in value are always interpreted as hexadecimal characters. Valid hexadecimal characters are 0-9, A-F, and a-f. The only other flags that can be combined with the style parameter are NumberStyles.AllowLeadingWhite and NumberStyles.AllowTrailingWhite. (The NumberStyles enumeration includes a composite number style, HexNumber, that includes both white-space flags.)

Note

If value is the string representation of a hexadecimal number, it cannot be preceded by any decoration (such as 0x or &h) that differentiates it as a hexadecimal number. This causes the conversion to fail.

If value is a hexadecimal string, the Parse(String, NumberStyles) method interprets value as a negative number stored by using two's complement representation if its first two hexadecimal digits are greater than or equal to 0x80. In other words, the method interprets the highest-order bit of the first byte in value as the sign bit. To make sure that a hexadecimal string is correctly interpreted as a positive number, the first digit in value must have a value of zero. For example, the method interprets 0x80 as a negative value, but it interprets either 0x080 or 0x0080 as a positive value. The following example illustrates the difference between hexadecimal strings that represent negative and positive values.

C#

using System;
using System.Globalization;
using System.Numerics;

public class Example
{
   public static void Main()
   {
      string[] hexStrings = { "80", "E293", "F9A2FF", "FFFFFFFF",
                              "080", "0E293", "0F9A2FF", "0FFFFFFFF",
                              "0080", "00E293", "00F9A2FF", "00FFFFFFFF" };
      foreach (string hexString in hexStrings)
      {
         BigInteger number = BigInteger.Parse(hexString, NumberStyles.AllowHexSpecifier);
         Console.WriteLine("Converted 0x{0} to {1}.", hexString, number);
      }
   }
}
// The example displays the following output:
//       Converted 0x80 to -128.
//       Converted 0xE293 to -7533.
//       Converted 0xF9A2FF to -417025.
//       Converted 0xFFFFFFFF to -1.
//       Converted 0x080 to 128.
//       Converted 0x0E293 to 58003.
//       Converted 0x0F9A2FF to 16360191.
//       Converted 0x0FFFFFFFF to 4294967295.
//       Converted 0x0080 to 128.
//       Converted 0x00E293 to 58003.
//       Converted 0x00F9A2FF to 16360191.
//       Converted 0x00FFFFFFFF to 4294967295.

The provider parameter is an IFormatProvider implementation. Its GetFormat method returns a NumberFormatInfo object that provides culture-specific information about the format of value. Typically, provider can be any one of the following:

• A CultureInfo object that represents the culture that provides numeric formatting information. Its GetFormat method returns the NumberFormatInfo object that provides numeric formatting information.

• A NumberFormatInfo object that provides formatting information. (Its implementation of GetFormat just returns itself.)

• A custom object that implements IFormatProvider and uses the GetFormat method to instantiate and return the NumberFormatInfo object that provides formatting information.

If provider is null, the NumberFormatInfo object for the current culture is used.

See also

• TryParse