Článek
11/17/2011

Decimal.TryParse Method (String, Decimal%)

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Converts the string representation of a number to its Decimal equivalent. A return value indicates whether the conversion succeeded or failed.

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

Syntax

'Declaration
Public Shared Function TryParse ( _
    s As String, _
    <OutAttribute> ByRef result As Decimal _
) As Boolean

public static bool TryParse(
    string s,
    out decimal result
)

Parameters

s
Type: System.String
The string representation of the number to convert.

result
Type: System.Decimal%
When this method returns, contains the Decimal number that is equivalent to the numeric value contained in s, if the conversion succeeded, or is zero if the conversion failed. The conversion fails if the s parameter is nulla null reference (Nothing in Visual Basic), is not a number in a valid format, or represents a number less than MinValue or greater than MaxValue. This parameter is passed uninitialized.

Return Value

Type: System.Boolean
true if s was converted successfully; otherwise, false.

Remarks

This overload differs from the Decimal.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.

Parameter s contains a number of the form:

[ws][sign][digits,]digits[.fractional-digits][ws]

Elements in square brackets ([ and ]) are optional. The following table describes each element.

Element	Description
ws	Optional white space.
sign	An optional sign.
digits	A sequence of digits ranging from 0 to 9.
,	A culture-specific thousands separator symbol.
.	A culture-specific decimal point symbol.
fractional-digits	A sequence of digits ranging from 0 to 9.

Parameter s is interpreted using the NumberStyles.Number style. 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 Decimal.TryParse(String, NumberStyles, IFormatProvider, Decimal%) method overload.

Parameter s is parsed using the formatting information in a NumberFormatInfo object initialized for the current system culture. For more information, see CurrentInfo. To parse a string using the formatting information of some other specified culture, use the Decimal.TryParse(String, NumberStyles, IFormatProvider, Decimal%) method overload.

If necessary, the value of s is rounded using rounding to nearest.

A Decimal object has 29 digits of precision. If s represents a number that has more than 29 digits, but has a fractional part and is within the range of MaxValue and MinValue, the number is rounded, not truncated, to 29 digits using rounding to nearest.

If during a parse operation a separator is encountered in the s parameter, 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.

Examples

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

Dim value As String
Dim number As Decimal

' Parse a floating-point value with a thousands separator.
value = "1,643.57"
If Decimal.TryParse(value, number) Then
   outputBlock.Text &= number & vbCrLf
Else
   outputBlock.Text &= String.Format("Unable to parse '{0}'.", value) & vbCrLf
End If

' Parse a floating-point value with a currency symbol and a 
' thousands separator.
value = "$1,643.57"
If Decimal.TryParse(value, number) Then
   outputBlock.Text &= number & vbCrLf
Else
   outputBlock.Text &= String.Format("Unable to parse '{0}'.", value) & vbCrLf
End If

' Parse value in exponential notation.
value = "-1.643e6"
If Decimal.TryParse(value, number) Then
   outputBlock.Text &= number & vbCrLf
Else
   outputBlock.Text &= String.Format("Unable to parse '{0}'.", value) & vbCrLf
End If

' Parse a negative integer value.
value = "-1689346178821"
If Decimal.TryParse(value, number) Then
   outputBlock.Text &= number & vbCrLf
Else
   outputBlock.Text &= String.Format("Unable to parse '{0}'.", value) & vbCrLf
End If
' The example displays the following output:
'       1643.57
'       Unable to parse '$1,643.57'.
'       Unable to parse '-1.643e6'.
'       -1689346178821

string value;
decimal number;

// Parse a floating-point value with a thousands separator.
value = "1,643.57";
if (Decimal.TryParse(value, out number))
   outputBlock.Text += number + "\n";
else
   outputBlock.Text += String.Format("Unable to parse '{0}'.", value) + "\n";

// Parse a floating-point value with a currency symbol and a 
// thousands separator.
value = "$1,643.57";
if (Decimal.TryParse(value, out number))
   outputBlock.Text += number + "\n";
else
   outputBlock.Text += String.Format("Unable to parse '{0}'.", value) + "\n";

// Parse value in exponential notation.
value = "-1.643e6";
if (Decimal.TryParse(value, out number))
   outputBlock.Text += number + "\n";
else
   outputBlock.Text += String.Format("Unable to parse '{0}'.", value) + "\n";

// Parse a negative integer value.
value = "-1689346178821";
if (Decimal.TryParse(value, out number))
   outputBlock.Text += number + "\n";
else
   outputBlock.Text += String.Format("Unable to parse '{0}'.", value) + "\n";
// The example displays the following output:
//       1643.57
//       Unable to parse '$1,643.57'.
//       Unable to parse '-1.643e6'.
//       -1689346178821

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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