Double.TryParse Method (String, Double)
Converts the string representation of a number to its double-precision floating-point number equivalent. A return value indicates whether the conversion succeeded or failed.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function TryParse ( s As String, <OutAttribute> ByRef result As Double ) As Boolean
Parameters
- s
-
Type:
System.String
A string containing a number to convert.
- result
-
Type:
System.Double
When this method returns, contains the double-precision floating-point number equivalent of the s parameter, if the conversion succeeded, or zero if the conversion failed. The conversion fails if the s parameter is null or String.Empty, is not a number in a valid format, or represents a number less than MinValue or greater than MaxValue. This parameter is passed uninitialized; any value originally supplied in result will be overwritten.
This overload differs from the Double.Parse(String) method by returning a Boolean value that indicates whether the parse operation succeeded instead of returning the parsed numeric value. It eliminates the need to use exception handling to test for a FormatException in the event that s is invalid and cannot be successfully parsed.
The s parameter can contain the current culture's NumberFormatInfo.PositiveInfinitySymbol, NumberFormatInfo.NegativeInfinitySymbol, NumberFormatInfo.NaNSymbol (the string comparison is case-sensitive), or a string of the form:
[ws][sign][integral-digits,]integral-digits[.[fractional-digits]][e[sign]exponential-digits][ws]
Elements in square brackets are optional. The following table describes each element.
Element | Description |
|---|---|
ws | A series of white-space characters. |
sign | A negative sign or positive sign symbol. |
integral-digits | A series of numeric characters ranging from 0 to 9 that specify the integral part of the number. Integral-digits can be absent if there are fractional-digits. |
, | A culture-specific group separator symbol. |
. | A culture-specific decimal point symbol. |
fractional-digits | A series of numeric characters ranging from 0 to 9 that specify the fractional part of the number. |
E | An uppercase or lowercase character 'e', that indicates exponential (scientific) notation. |
exponential-digits | A series of numeric characters ranging from 0 to 9 that specify an exponent. |
For more information about numeric formats, see Formatting Types in the .NET Framework.
The s parameter is interpreted by using a combination of the NumberStyles.Float and NumberStyles.AllowThousands flags. This means that white space and thousands separators are allowed but currency symbols are not. To explicitly define the elements (such as currency symbols, thousands separators, and white space) that can be present in s, use the Double.TryParse(String, NumberStyles, IFormatProvider, Double) method overload.
The s parameter is parsed using the formatting information in a NumberFormatInfo object that is initialized for the current system culture. For more information, see NumberFormatInfo.CurrentInfo. To parse a string using the formatting information of some other specified culture, use the Double.TryParse(String, NumberStyles, IFormatProvider, Double) method overload.
Ordinarily, if you pass the Double.TryParse 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.
Module Example Public Sub Main() Dim value As String Dim number As Double value = Double.MinValue.ToString() If Double.TryParse(value, number) Then Console.WriteLine(number) Else Console.WriteLine("{0} is outside the range of a Double.", _ value) End If value = Double.MaxValue.ToString() If Double.TryParse(value, number) Then Console.WriteLine(number) Else Console.WriteLine("{0} is outside the range of a Double.", _ value) End If End Sub End Module ' 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 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 uses the TryParse(String, Double) method to convert the string representations of numeric values to Double values. It assumes that en-US is the current culture.
Module Example Public Sub Main() Dim values() As String = { "1,643.57", "$1,643.57", "-1.643e6", "-168934617882109132", "123AE6", Nothing, String.Empty, "ABCDEF" } Dim number As Double For Each value In values If Double.TryParse(value, number) Then Console.WriteLine("'{0}' --> {1}", value, number) Else Console.WriteLine("Unable to parse '{0}'.", value) End If Next End Sub End Module ' The example displays the following output: ' '1,643.57' --> 1643.57 ' Unable to parse '$1,643.57'. ' '-1.643e6' --> -1643000 ' '-168934617882109132' --> -1.68934617882109E+17 ' Unable to parse '123AE6'. ' Unable to parse ''. ' Unable to parse ''. ' Unable to parse 'ABCDEF'.
Available since 8
.NET Framework
Available since 2.0
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