Single.TryParse Method (String, Single)

 

Converts the string representation of a number to its single-precision floating-point number equivalent. A return value indicates whether the conversion succeeded or failed.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

Public Shared Function TryParse (
	s As String,
	<OutAttribute> ByRef result As Single
) As Boolean

Parameters

s
Type: System.String

A string representing a number to convert.

result
Type: System.Single

When this method returns, contains single-precision floating-point number equivalent to the numeric value or symbol contained in s, 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.

Return Value

Type: System.Boolean

true if s was converted successfully; otherwise, false.

This overload differs from the Single.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 PositiveInfinitySymbol, NegativeInfinitySymbol, 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.

The s parameter is interpreted 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 TryParse(String, NumberStyles, IFormatProvider, Single) 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 TryParse(String, NumberStyles, IFormatProvider, Single) method overload.

Ordinarily, if you pass the Single.TryParse method a string that is created by calling the Single.ToString method, the original Single value is returned. However, because of a loss of precision, the values may not be equal.

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 uses the TryParse(String, Single) method to convert the string representations of numeric values to Single values. It assumes that en-US is the current culture.

Dim value As String
Dim number As Single

' Parse a floating-point value with a thousands separator.
value = "1,643.57"
If Single.TryParse(value, number) Then
   Console.WriteLine(number)
Else
   Console.WriteLine("Unable to parse '{0}'.", value)      
End If   

' Parse a floating-point value with a currency symbol and a 
' thousands separator.
value = "$1,643.57"
If Single.TryParse(value, number) Then
   Console.WriteLine(number)  
Else
   Console.WriteLine("Unable to parse '{0}'.", value)   
End If

' Parse value in exponential notation.
value = "-1.643e6"
If Single.TryParse(value, number)
   Console.WriteLine(number)
Else
   Console.WriteLine("Unable to parse '{0}'.", value)   
End If

' Parse a negative integer number.
value = "-168934617882109132"
If Single.TryParse(value, number)
   Console.WriteLine(number)
Else
   Console.WriteLine("Unable to parse '{0}'.", value)   
End If
' The example displays the following output:
'       1643.57
'       Unable to parse '$1,643.57'.
'       -1643000
'       -1.68934617882109E+17

Universal Windows Platform
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
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