Double.Parse Method (String, NumberStyles, IFormatProvider)
Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function Parse ( s As String, style As NumberStyles, provider As IFormatProvider ) As Double
Parameters
- s
-
Type:
System.String
A string that contains a number to convert.
- style
-
Type:
System.Globalization.NumberStyles
A bitwise combination of enumeration values that indicate the style elements that can be present in s. A typical value to specify is Float combined with AllowThousands.
- provider
-
Type:
System.IFormatProvider
An object that supplies culture-specific formatting information about s.
Return Value
Type: System.DoubleA double-precision floating-point number that is equivalent to the numeric value or symbol specified in s.
| Exception | Condition |
|---|---|
| ArgumentNullException | s is null. |
| FormatException | s does not represent a numeric value. |
| ArgumentException | |
| OverflowException |
The style parameter defines the style elements (such as white space, thousands separators, and currency symbols) that are allowed in the s parameter for the parse operation to succeed. It must be a combination of bit flags from the NumberStyles enumeration. The following NumberStyles members are not supported:
The s parameter can contain NumberFormatInfo.PositiveInfinitySymbol, NumberFormatInfo.NegativeInfinitySymbol, or NumberFormatInfo.NaNSymbol for the culture specified by provider. Depending on the value of style, it can also take the form:
[ws] [$] [sign][integral-digits,]integral-digits[.[fractional-digits]][E[sign]exponential-digits][ws]
Elements framed in square brackets ([ and ]) are optional. The following table describes each element.
Element | Description |
|---|---|
ws | A series of white-space characters. White space can appear at the beginning of s if style includes the NumberStyles.AllowLeadingWhite flag, and it can appear at the end of s 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 s if style includes the NumberStyles.AllowCurrencySymbol flag. |
sign | A negative sign symbol (-) or a positive sign symbol (+). The sign can appear at the beginning of s if style includes the NumberStyles.AllowLeadingSign flag, and it can appear at the end of s if style includes the NumberStyles.AllowTrailingSign flag. Parentheses can be used in s to indicate a negative value if style includes the NumberStyles.AllowParentheses flag. |
integral-digits | A series of digits ranging from 0 to 9 that specify the integral part of the number. The integral-digits element can be absent if the string contains the fractional-digits element. |
, | A culture-specific group separator. The current culture's group separator symbol can appear in s if style includes the NumberStyles.AllowThousands flag |
. | A culture-specific decimal point symbol. The current culture's decimal point symbol can appear in s if style includes the NumberStyles.AllowDecimalPoint flag. |
fractional-digits | A series of digits ranging from 0 to 9 that specify the fractional part of the number. Fractional digits can appear in s if style includes the NumberStyles.AllowDecimalPoint flag. |
E | The "e" or "E" character, which indicates that the value is represented in exponential (scientific) notation. The s parameter can represent a number in exponential notation if style includes the NumberStyles.AllowExponent flag. |
exponential-digits | A series of digits ranging from 0 to 9 that specify an exponent. |
A string with digits only (which corresponds to the NumberStyles.None style) always parses successfully. The remaining System.Globalization.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 flags affect the elements that may be present in s.
NumberStyles value | Elements permitted in s in addition to digits |
|---|---|
The integral-digits element only. | |
The decimal point (.) and fractional-digits elements. | |
The "e" or "E" character, which indicates exponential notation. This flag by itself supports values in the form digitsEdigits; additional flags are needed to successfully parse strings with such elements as positive or negative signs and decimal point symbols. | |
The ws element at the beginning of s. | |
The ws element at the end of s. | |
The sign element at the beginning of s. | |
The sign element at the end of s. | |
The sign element in the form of parentheses enclosing the numeric value. | |
The thousands separator (,) element. | |
The currency ($) element. | |
All elements. However, s cannot represent a hexadecimal number or a number in exponential notation. | |
The ws element at the beginning or end of s, sign at the beginning of s, and the decimal point (.) symbol. The s parameter can also use exponential notation. | |
The ws, sign, thousands separator (,) and decimal point (.) elements. | |
All elements. However, s cannot represent a hexadecimal number. |
The provider parameter is an IFormatProvider implementation whose GetFormat method returns a NumberFormatInfo object that supplies culture-specific information used in interpreting the format of s. Typically, it is a NumberFormatInfo or CultureInfo object. If provider is null or a NumberFormatInfo cannot be obtained, the formatting information for the current system culture is used.
Ordinarily, if you pass the Double.Parse method a string that is created by calling the Double.ToString method, the original Double value is returned. However, because of a loss of precision, the values may not be equal. In addition, attempting to parse the string representation of either MinValue or MaxValue throws an OverflowException, as the following example illustrates.
Dim value As String value = Double.MinValue.ToString() Try Console.WriteLine(Double.Parse(value)) Catch e As OverflowException Console.WriteLine("{0} is outside the range of the Double type.", _ value) End Try value = Double.MaxValue.ToString() Try Console.WriteLine(Double.Parse(value)) Catch e As OverflowException Console.WriteLine("{0} is outside the range of the Double type.", _ value) End Try ' The example displays the following output: ' -1.79769313486232E+308 is outside the range of the Double type. ' 1.79769313486232E+308 is outside the range of the Double type.
If a separator is encountered in the s parameter during a parse operation, and the applicable currency or number decimal and group separators are the same, the parse operation assumes that the separator is a decimal separator rather than a group separator. For more information about separators, see CurrencyDecimalSeparator, NumberDecimalSeparator, CurrencyGroupSeparator, and NumberGroupSeparator.
The following example illustrates the use of the Parse(String, NumberStyles, IFormatProvider) method to assign several string representations of temperature values to a Temperature object.
Imports System.Globalization Public Class Temperature ' Parses the temperature from a string. Temperature scale is ' indicated by 'F (for Fahrenheit) or 'C (for Celcius) at the end ' of the string. Public Shared Function Parse(s As String, styles As NumberStyles, _ provider As IFormatProvider) As Temperature Dim temp As New Temperature() If s.TrimEnd(Nothing).EndsWith("'F") Then temp.Value = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), _ styles, provider) Else If s.TrimEnd(Nothing).EndsWith("'C") Then temp.Celsius = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), _ styles, provider) Else temp.Value = Double.Parse(s, styles, provider) End If End If Return temp End Function ' Declare private constructor so Temperature so only Parse method can ' create a new instance Private Sub New End Sub Protected m_value As Double Public Property Value() As Double Get Return m_value End Get Private Set m_value = Value End Set End Property Public Property Celsius() As Double Get Return (m_value - 32) / 1.8 End Get Private Set m_value = Value * 1.8 + 32 End Set End Property Public ReadOnly Property Fahrenheit() As Double Get Return m_Value End Get End Property End Class Public Module TestTemperature Public Sub Main Dim value As String Dim styles As NumberStyles Dim provider As IFormatProvider Dim temp As Temperature value = "25,3'C" styles = NumberStyles.Float provider = CultureInfo.CreateSpecificCulture("fr-FR") temp = Temperature.Parse(value, styles, provider) Console.WriteLine("{0} degrees Fahrenheit equals {1} degrees Celsius.", _ temp.Fahrenheit, temp.Celsius) value = " (40) 'C" styles = NumberStyles.AllowLeadingWhite Or NumberStyles.AllowTrailingWhite _ Or NumberStyles.AllowParentheses provider = NumberFormatInfo.InvariantInfo temp = Temperature.Parse(value, styles, provider) Console.WriteLine("{0} degrees Fahrenheit equals {1} degrees Celsius.", _ temp.Fahrenheit, temp.Celsius) value = "5,778E03'C" ' Approximate surface temperature of the Sun styles = NumberStyles.AllowDecimalPoint Or NumberStyles.AllowThousands Or _ NumberStyles.AllowExponent provider = CultureInfo.CreateSpecificCulture("en-GB") temp = Temperature.Parse(value, styles, provider) Console.WriteLine("{0} degrees Fahrenheit equals {1} degrees Celsius.", _ temp.Fahrenheit.ToString("N"), temp.Celsius.ToString("N")) End Sub End Module
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1