Článek
11/18/2011

Int32.TryParse Method (String, Int32%)

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Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the conversion succeeded.

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

Syntax

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

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

Parameters

s
Type: System.String
A string containing a number to convert.

result
Type: System.Int32%
When this method returns, contains the 32-bit signed integer value equivalent to the number contained in s, 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 of the correct 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

The TryParse method is like the Parse method, except the TryParse method does not throw an exception if the conversion fails. 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 contains a number of the form:

[ws][sign]digits[ws]

Items 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.

The s parameter is interpreted using the NumberStyles.Integer style. In addition to the decimal digits, only leading and trailing spaces together with a leading sign are allowed. To explicitly define the style elements together with the culture-specific formatting information that can be present in s, use the Int32.TryParse(String, NumberStyles, IFormatProvider, Int32%) method.

The s parameter is parsed using the formatting information in a NumberFormatInfo object initialized for the current system culture. For more information, see CurrentInfo.

This overload of the TryParse method interprets all digits in the s parameter as decimal digits. To parse the string representation of a hexadecimal number, call the Int32.TryParse(String, NumberStyles, IFormatProvider, Int32%) overload.

Examples

The following example calls the Int32.TryParse(String, Int32%) method with a number of different string values.

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      TryToParse(outputBlock, Nothing)
      TryToParse(outputBlock, "160519")
      TryToParse(outputBlock, "9432.0")
      TryToParse(outputBlock, "16,667")
      TryToParse(outputBlock, "   -322   ")
      TryToParse(outputBlock, "+4302")
      TryToParse(outputBlock, "(100)")
      TryToParse(outputBlock, "01FA")
   End Sub

   Private Sub TryToParse(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal value As String)
      Dim number As Integer
      Dim result As Boolean = Int32.TryParse(value, number)
      If result Then
         outputBlock.Text += String.Format("Converted '{0}' to {1}.", value, number) & vbCrLf
      Else
         If value Is Nothing Then value = ""
         outputBlock.Text += String.Format("Attempted conversion of '{0}' failed.", value) & vbCrLf
      End If
   End Sub
End Module
' The example displays the following output:
'       Attempted conversion of '' failed.
'       Converted '160519' to 160519.
'       Attempted conversion of '9432.0' failed.
'       Attempted conversion of '16,667' failed.
'       Converted '   -322   ' to -322.
'       Converted '+4302' to 4302.
'       Attempted conversion of '(100)' failed.
'       Attempted conversion of '01FA' failed.

using System;

public class Example
{
   private static System.Windows.Controls.TextBlock outputBlock;

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Example.outputBlock = outputBlock;

      TryToParse(null);
      TryToParse("160519");
      TryToParse("9432.0");
      TryToParse("16,667");
      TryToParse("   -322   ");
      TryToParse("+4302");
      TryToParse("(100)");
      TryToParse("01FA");
   }

   private static void TryToParse(string value)
   {
      int number;
      bool result = Int32.TryParse(value, out number);
      if (result)
      {
         outputBlock.Text += String.Format("Converted '{0}' to {1}.", value, number) + "\n";
      }
      else
      {
         if (value == null) value = "";
         outputBlock.Text += String.Format("Attempted conversion of '{0}' failed.", value) + "\n";
      }
   }
}
// The example displays the following output:
//       Attempted conversion of '' failed.
//       Converted '160519' to 160519.
//       Attempted conversion of '9432.0' failed.
//       Attempted conversion of '16,667' failed.
//       Converted '   -322   ' to -322.
//       Converted '+4302' to 4302.
//       Attempted conversion of '(100);' failed.
//       Attempted conversion of '01FA' failed.

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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