All numeric types have two static parsing methods, Parse and TryParse, that you can use to convert the string representation of a number into a numeric type. These methods enable you to parse strings that were produced by using the format strings documented in Standard Numeric Format Strings and Custom Numeric Format Strings. By default, the Parse and TryParse methods can successfully convert strings that contain integral decimal digits only to integer values. They can successfully convert strings that contain integral and fractional decimal digits, group separators, and a decimal separator to floating-point values. The Parse method throws an exception if the operation fails, whereas the TryParse method returns false.
Parsing and format providers
Typically, the string representations of numeric values differ by culture. Elements of numeric strings, such as currency symbols, group (or thousands) separators, and decimal separators, all vary by culture. Parsing methods either implicitly or explicitly use a format provider that recognizes these culture-specific variations. If no format provider is specified in a call to the Parse or TryParse method, the format provider associated with the current culture (the System.Globalization.NumberFormatInfo object returned by the System.Globalization.NumberFormatInfo.CurrentInfo property) is used.
A format provider is represented by an System.IFormatProvider implementation. This interface has a single member, the System.IFormatProvider.GetFormat method, whose single parameter is a System.Type object that represents the type to be formatted. This method returns the object that provides formatting information. .NET supports the following two System.IFormatProvider implementations for parsing numeric strings:
A System.Globalization.CultureInfo object whose System.Globalization.CultureInfo.GetFormat method returns a System.Globalization.NumberFormatInfo object that provides culture-specific formatting information.
A System.Globalization.NumberFormatInfo object whose System.Globalization.NumberFormatInfo.GetFormat method returns itself.
The following example tries to convert each string in an array to a System.Double value. It first tries to parse the string by using a format provider that reflects the conventions of the English (United States) culture. If this operation throws a System.FormatException, it tries to parse the string by using a format provider that reflects the conventions of the French (France) culture.
sample · csharpsamples/snippets/csharp/VS_Snippets_CLR/parsing.numbers/cs/formatproviders1.cs1
// <Snippet1>
using System;
using System.Globalization;
public class Example
{
public static void Main()
{
string[] values = { "1,304.16", "$1,456.78", "1,094", "152",
"123,45 €", "1 304,16", "Ae9f" };
double number;
CultureInfo culture = null;
foreach (string value in values) {
try {
culture = CultureInfo.CreateSpecificCulture("en-US");
number = Double.Parse(value, culture);
Console.WriteLine($"{culture.Name}: {value} --> {number}");
}
catch (FormatException) {
Console.WriteLine($"{culture.Name}: Unable to parse '{value}'.");
culture = CultureInfo.CreateSpecificCulture("fr-FR");
try {
number = Double.Parse(value, culture);
Console.WriteLine($"{culture.Name}: {value} --> {number}");
}
catch (FormatException) {
Console.WriteLine($"{culture.Name}: Unable to parse '{value}'.");
}
}
Console.WriteLine();
}
}
}
// The example displays the following output:
// en-US: 1,304.16 --> 1304.16
//
// en-US: Unable to parse '$1,456.78'.
// fr-FR: Unable to parse '$1,456.78'.
//
// en-US: 1,094 --> 1094
//
// en-US: 152 --> 152
//
// en-US: Unable to parse '123,45 €'.
// fr-FR: Unable to parse '123,45 €'.
//
// en-US: Unable to parse '1 304,16'.
// fr-FR: 1 304,16 --> 1304.16
//
// en-US: Unable to parse 'Ae9f'.
// fr-FR: Unable to parse 'Ae9f'.
// </Snippet1>sample · vbsamples/snippets/visualbasic/VS_Snippets_CLR/parsing.numbers/vb/formatproviders1.vb1
' Visual Basic .NET Document
Option Strict On
' <Snippet1>
Imports System.Globalization
Module Example
Public Sub Main()
Dim values() As String = {"1,304.16", "$1,456.78", "1,094", "152",
"123,45 €", "1 304,16", "Ae9f"}
Dim number As Double
Dim culture As CultureInfo = Nothing
For Each value As String In values
Try
culture = CultureInfo.CreateSpecificCulture("en-US")
number = Double.Parse(value, culture)
Console.WriteLine("{0}: {1} --> {2}", culture.Name, value, number)
Catch e As FormatException
Console.WriteLine("{0}: Unable to parse '{1}'.",
culture.Name, value)
culture = CultureInfo.CreateSpecificCulture("fr-FR")
Try
number = Double.Parse(value, culture)
Console.WriteLine("{0}: {1} --> {2}", culture.Name, value, number)
Catch ex As FormatException
Console.WriteLine("{0}: Unable to parse '{1}'.",
culture.Name, value)
End Try
End Try
Console.WriteLine()
Next
End Sub
End Module
' The example displays the following output:
' en-US: 1,304.16 --> 1304.16
'
' en-US: Unable to parse '$1,456.78'.
' fr-FR: Unable to parse '$1,456.78'.
'
' en-US: 1,094 --> 1094
'
' en-US: 152 --> 152
'
' en-US: Unable to parse '123,45 €'.
' fr-FR: Unable to parse '123,45 €'.
'
' en-US: Unable to parse '1 304,16'.
' fr-FR: 1 304,16 --> 1304.16
'
' en-US: Unable to parse 'Ae9f'.
' fr-FR: Unable to parse 'Ae9f'.
' </Snippet1>Parsing and NumberStyles Values
The style elements (such as white space, group separators, and decimal separator) that the parse operation can handle are defined by a System.Globalization.NumberStyles enumeration value. By default, strings that represent integer values are parsed by using the System.Globalization.NumberStyles.Integer value, which permits only numeric digits, leading and trailing white space, and a leading sign. Strings that represent floating-point values are parsed using a combination of the System.Globalization.NumberStyles.Float and System.Globalization.NumberStyles.AllowThousands values; this composite style permits decimal digits along with leading and trailing white space, a leading sign, a decimal separator, a group separator, and an exponent. By calling an overload of the Parse or TryParse method that includes a parameter of type System.Globalization.NumberStyles and setting one or more System.Globalization.NumberStyles flags, you can control the style elements that can be present in the string for the parse operation to succeed.
For example, a string that contains a group separator can't be converted to an System.Int32 value by using the System.Int32.Parse%28System.String%29 method. However, the conversion succeeds if you use the System.Globalization.NumberStyles.AllowThousands flag, as the following example illustrates.
sample · csharpsamples/snippets/csharp/VS_Snippets_CLR/parsing.numbers/cs/styles1.cs2
// <Snippet2>
using System;
using System.Globalization;
public class Example
{
public static void Main()
{
string value = "1,304";
int number;
IFormatProvider provider = CultureInfo.CreateSpecificCulture("en-US");
if (Int32.TryParse(value, out number))
Console.WriteLine($"{value} --> {number}");
else
Console.WriteLine($"Unable to convert '{value}'");
if (Int32.TryParse(value, NumberStyles.Integer | NumberStyles.AllowThousands,
provider, out number))
Console.WriteLine($"{value} --> {number}");
else
Console.WriteLine($"Unable to convert '{value}'");
}
}
// The example displays the following output:
// Unable to convert '1,304'
// 1,304 --> 1304
// </Snippet2>sample · vbsamples/snippets/visualbasic/VS_Snippets_CLR/parsing.numbers/vb/styles1.vb2
' Visual Basic .NET Document
Option Strict On
' <Snippet2>
Imports System.Globalization
Module Example
Public Sub Main()
Dim value As String = "1,304"
Dim number As Integer
Dim provider As IFormatProvider = CultureInfo.CreateSpecificCulture("en-US")
If Int32.TryParse(value, number) Then
Console.WriteLine("{0} --> {1}", value, number)
Else
Console.WriteLine("Unable to convert '{0}'", value)
End If
If Int32.TryParse(value, NumberStyles.Integer Or NumberStyles.AllowThousands,
provider, number) Then
Console.WriteLine("{0} --> {1}", value, number)
Else
Console.WriteLine("Unable to convert '{0}'", value)
End If
End Sub
End Module
' The example displays the following output:
' Unable to convert '1,304'
' 1,304 --> 1304
' </Snippet2>The following table lists the members of the System.Globalization.NumberStyles enumeration and describes the effect that they have on the parsing operation.
| NumberStyles value | Effect on the string to be parsed |
|---|---|
| System.Globalization.NumberStyles.None | Only numeric digits are permitted. |
| System.Globalization.NumberStyles.AllowDecimalPoint | The decimal separator and fractional digits are permitted. For integer values, only zero is permitted as a fractional digit. Valid decimal separators are determined by the System.Globalization.NumberFormatInfo.NumberDecimalSeparator or System.Globalization.NumberFormatInfo.CurrencyDecimalSeparator property. |
| System.Globalization.NumberStyles.AllowExponent | The "e" or "E" character can be used to indicate exponential notation. For more information, see System.Globalization.NumberStyles. |
| System.Globalization.NumberStyles.AllowLeadingWhite | Leading white space is permitted. |
| System.Globalization.NumberStyles.AllowTrailingWhite | Trailing white space is permitted. |
| System.Globalization.NumberStyles.AllowLeadingSign | A positive or negative sign can precede numeric digits. |
| System.Globalization.NumberStyles.AllowTrailingSign | A positive or negative sign can follow numeric digits. |
| System.Globalization.NumberStyles.AllowParentheses | Parentheses can be used to indicate negative values. |
| System.Globalization.NumberStyles.AllowThousands | The group separator is permitted. The group separator character is determined by the System.Globalization.NumberFormatInfo.NumberGroupSeparator or System.Globalization.NumberFormatInfo.CurrencyGroupSeparator property. |
| System.Globalization.NumberStyles.AllowCurrencySymbol | The currency symbol is permitted. The currency symbol is defined by the System.Globalization.NumberFormatInfo.CurrencySymbol property. |
| System.Globalization.NumberStyles.AllowHexSpecifier | The string to be parsed is interpreted as a hexadecimal number. It can include the hexadecimal digits 0-9, A-F, and a-f. This flag can be used only to parse integer values. |
| System.Globalization.NumberStyles.AllowBinarySpecifier | The string to be parsed is interpreted as a binary number. It can include the binary digits 0 and 1. This flag can be used only to parse integer values. |
In addition, the System.Globalization.NumberStyles enumeration provides the following composite styles, which include multiple System.Globalization.NumberStyles flags.
Parsing binary and hexadecimal BigIntegers
When parsing System.Numerics.BigInteger with the System.Globalization.NumberStyles.AllowHexSpecifier or System.Globalization.NumberStyles.AllowBinarySpecifier flags, the input string is interpreted as a hexadecimal/binary number of exactly the length the string has. For instance, parsing "11" as a binary BigInteger yields -1, because that is the interpretation of 11 as a signed two's complement value with exactly 2 digits. If you want a positive result, add a leading 0, such as "011" which is parsed as 3.
Parsing and Unicode Digits
The Unicode standard defines code points for digits in various writing systems. For example, code points from U+0030 to U+0039 represent the basic Latin digits 0 through 9, code points from U+09E6 to U+09EF represent the Bangla digits 0 through 9, and code points from U+FF10 to U+FF19 represent the Fullwidth digits 0 through 9. However, the only numeric digits recognized by parsing methods are the basic Latin digits 0-9 with code points from U+0030 to U+0039. If a numeric parsing method is passed a string that contains any other digits, the method throws a System.FormatException.
The following example uses the System.Int32.Parse method to parse strings that consist of digits in different writing systems. As the output from the example shows, the attempt to parse the basic Latin digits succeeds, but the attempt to parse the Fullwidth, Arabic-Indic, and Bangla digits fails.
sample · csharpsamples/snippets/csharp/VS_Snippets_CLR/parsing.numbers/cs/unicode1.cs3
// <Snippet3>
using System;
public class Example
{
public static void Main()
{
string value;
// Define a string of basic Latin digits 1-5.
value = "\u0031\u0032\u0033\u0034\u0035";
ParseDigits(value);
// Define a string of Fullwidth digits 1-5.
value = "\uFF11\uFF12\uFF13\uFF14\uFF15";
ParseDigits(value);
// Define a string of Arabic-Indic digits 1-5.
value = "\u0661\u0662\u0663\u0664\u0665";
ParseDigits(value);
// Define a string of Bangla digits 1-5.
value = "\u09e7\u09e8\u09e9\u09ea\u09eb";
ParseDigits(value);
}
static void ParseDigits(string value)
{
try {
int number = Int32.Parse(value);
Console.WriteLine($"'{value}' --> {number}");
}
catch (FormatException) {
Console.WriteLine($"Unable to parse '{value}'.");
}
}
}
// The example displays the following output:
// '12345' --> 12345
// Unable to parse '１２３４５'.
// Unable to parse '١٢٣٤٥'.
// Unable to parse '১২৩৪৫'.
// </Snippet3>sample · vbsamples/snippets/visualbasic/VS_Snippets_CLR/parsing.numbers/vb/unicode1.vb3
' Visual Basic .NET Document
Option Strict On
' <Snippet3>
Module Example
Public Sub Main()
Dim value As String
' Define a string of basic Latin digits 1-5.
value = ChrW(&h31) + ChrW(&h32) + ChrW(&h33) + ChrW(&h34) + ChrW(&h35)
ParseDigits(value)
' Define a string of Fullwidth digits 1-5.
value = ChrW(&hff11) + ChrW(&hff12) + ChrW(&hff13) + ChrW(&hff14) + ChrW(&hff15)
ParseDigits(value)
' Define a string of Arabic-Indic digits 1-5.
value = ChrW(&h661) + ChrW(&h662) + ChrW(&h663) + ChrW(&h664) + ChrW(&h665)
ParseDigits(value)
' Define a string of Bangla digits 1-5.
value = ChrW(&h09e7) + ChrW(&h09e8) + ChrW(&h09e9) + ChrW(&h09ea) + ChrW(&h09eb)
ParseDigits(value)
End Sub
Sub ParseDigits(value As String)
Try
Dim number As Integer = Int32.Parse(value)
Console.WriteLine("'{0}' --> {1}", value, number)
Catch e As FormatException
Console.WriteLine("Unable to parse '{0}'.", value)
End Try
End Sub
End Module
' The example displays the following output:
' '12345' --> 12345
' Unable to parse '１２３４５'.
' Unable to parse '١٢٣٤٥'.
' Unable to parse '১২৩৪৫'.
' </Snippet3>