Double.Parse Method (String, IFormatProvider)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Converts the string representation of a number in a specified culture-specific format to its double-precision floating-point number equivalent.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Shared Function Parse ( _ s As String, _ provider As IFormatProvider _ ) As Double
Parameters
- s
- Type: System.String
A string that contains a number to convert.
- 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 Nothing. |
| FormatException | s does not represent a number in a valid format. |
| OverflowException | s represents a number that is less than MinValue or greater than MaxValue. |
This overload of the Parse(String, IFormatProvider) method is typically used to convert text that can be formatted in a variety of ways to a Double value. For example, it can be used to convert the text that is entered by a user into an HTML text box to a numeric value.
The s parameter is interpreted using a combination of the NumberStyles.Float and NumberStyles.AllowThousands flags. The s parameter can contain NumberFormatInfo.PositiveInfinitySymbol, NumberFormatInfo.NegativeInfinitySymbol, or NumberFormatInfo.NaNSymbol for the culture specified by provider, or it can contain a string of the form:
[ws][sign]integral-digits[.[fractional-digits]][E[sign]exponential-digits][ws]
Optional elements are framed in square brackets ([ and ]). Elements that contain the term "digits" consist of a series of numeric characters ranging from 0 to 9.
Element | Description |
|---|---|
ws | A series of white-space characters. |
sign | A negative sign symbol (-) or a positive sign symbol (+). |
integral-digits | A series of digits ranging from 0 to 9 that specify the integral part of the number. Runs of integral-digits can be partitioned by a group-separator symbol. For example, in some cultures a comma (,) separates groups of thousands. The integral-digits element can be absent if the string contains the fractional-digits element. |
. | A culture-specific decimal point symbol. |
fractional-digits | A series of digits ranging from 0 to 9 that specify the fractional part of the number. |
E | The "e" or "E" character, which indicates that the value is represented in exponential (scientific) notation. |
exponential-digits | A series of digits ranging from 0 to 9 that specify an exponent. |
For more information about numeric formats, see the Formatting Types topic.
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 Nothing 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 outputBlock.Text += Double.Parse(value).ToString() + vbCrLf Catch e As OverflowException outputBlock.Text += String.Format("{0} is outside the range of the Double type.", _ value) + vbCrLf End Try value = Double.MaxValue.ToString() Try outputBlock.Text += Double.Parse(value).ToString() + vbCrLf Catch e As OverflowException outputBlock.Text += String.Format("{0} is outside the range of the Double type.", _ value) + vbCrLf 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 fallback cultures when parsing the string representation of a Double value. It first attempts to parse the string by using the current culture. If that operation fails, it attempts to parse the string by using the current culture's neutral culture. If that parse operation also fails, it attempts to parse the string by using the invariant culture. Only if that operation fails does it throw a FormatException.
Public Function GetDouble(value As String) As Double Dim culture As CultureInfo = Nothing Dim number As Double ' Throw exception if string is empty. If String.IsNullOrEmpty(value) Then _ Throw New ArgumentNullException("The input string is invalid.") ' Determine if value can be parsed using current culture. Try culture = CultureInfo.CurrentCulture number = Double.Parse(value, culture) Return number Catch End Try ' If Parse operation fails, see if there's a neutral culture. Try culture = culture.Parent number = Double.Parse(value, culture) Return number Catch End Try ' If there is no neutral culture or if parse operation fails, use ' the invariant culture. culture = CultureInfo.InvariantCulture Try number = Double.Parse(value, culture) Return number ' All attempts to parse the string have failed. Rethrow the exception. Catch e As FormatException Throw New FormatException(String.Format("Unable to parse '{0}'.", value), _ e) End Try End Function