Double.TryParse Method (String, Double%)
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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.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function TryParse ( _
s As String, _
<OutAttribute> ByRef result As Double _
) As Boolean
public static bool TryParse(
string s,
out double result
)
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 to the s parameter, if the conversion succeeded, or 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 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.
The s parameter s is interpreted using the 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 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.
Dim value As String
Dim number As Double
value = Double.MinValue.ToString()
If Double.TryParse(value, number) Then
outputBlock.Text += number.ToString() + vbCrLf
Else
outputBlock.Text += String.Format("{0} is outside the range of a Double.", _
value) + vbCrLf
End If
value = Double.MaxValue.ToString()
If Double.TryParse(value, number) Then
outputBlock.Text += number.ToString() + vbCrLf
Else
outputBlock.Text += String.Format("{0} is outside the range of a Double.", _
value) + vbCrLf
End If
' 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.
string value;
double number;
value = Double.MinValue.ToString();
if (Double.TryParse(value, out number))
outputBlock.Text += number.ToString() + "\n";
else
outputBlock.Text += String.Format("{0} is outside the range of a Double.\n",
value);
value = Double.MaxValue.ToString();
if (Double.TryParse(value, out number))
outputBlock.Text += number.ToString() + "\n";
else
outputBlock.Text += String.Format("{0} is outside the range of a Double.\n",
value);
// 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.
Examples
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.
Dim value As String
Dim number As Double
' Parse a floating-point value with a thousands separator.
value = "1,643.57"
If Double.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 Double.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 Double.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 number.
value = "-168934617882109132"
If Double.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'.
' -1643000
' -1.68934617882109E+17
string value;
double number;
// Parse a floating-point value with a thousands separator.
value = "1,643.57";
if (Double.TryParse(value, out number))
outputBlock.Text += number + "\n";
else
outputBlock.Text += String.Format("Unable to parse '{0}'.\n", value);
// Parse a floating-point value with a currency symbol and a
// thousands separator.
value = "$1,643.57";
if (Double.TryParse(value, out number))
outputBlock.Text += number + "\n";
else
outputBlock.Text += String.Format("Unable to parse '{0}'.\n", value);
// Parse value in exponential notation.
value = "-1.643e6";
if (Double.TryParse(value, out number))
outputBlock.Text += number + "\n";
else
outputBlock.Text += String.Format("Unable to parse '{0}'.\n", value);
// Parse a negative integer value.
value = "-168934617882109132";
if (Double.TryParse(value, out number))
outputBlock.Text += number + "\n";
else
outputBlock.Text += String.Format("Unable to parse '{0}'.\n", value);
// The example displays the following output:
// 1643.57
// Unable to parse '$1,643.57'.
// -164300
// -1.68934617882109E+17
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.
See Also