Поделиться через


Convert.ToByte Method (String, IFormatProvider)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Converts the specified String representation of a number to an equivalent 8-bit unsigned integer using specified culture-specific formatting information.

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

Syntax

'Declaration
Public Shared Function ToByte ( _
    value As String, _
    provider As IFormatProvider _
) As Byte
public static byte ToByte(
    string value,
    IFormatProvider provider
)

Parameters

Return Value

Type: System.Byte
An 8-bit signed integer equivalent to the value of value.
-or-
Zero if value is nulla null reference (Nothing in Visual Basic).

Exceptions

Exception Condition
FormatException

value does not consist of an optional sign followed by a sequence of digits (zero through nine).

OverflowException

value represents a number less than MinValue or greater than MaxValue.

Remarks

provider is an IFormatProvider instance that obtains a NumberFormatInfo object. The NumberFormatInfo object provides culture-specific information about the format of value. If provider is nulla null reference (Nothing in Visual Basic), the NumberFormatInfo for the current culture is used.

If you prefer not to handle an exception if the conversion fails, you can call the Byte.TryParse method instead. It returns a Boolean value that indicates whether the conversion succeeded or failed.

Examples

The following code example converts String representations of unsigned Byte values with the ToByte method, using an IFormatProvider object.

' Example of the Convert.ToByte( String ) and 
' Convert.ToByte( String, IFormatProvider ) methods.
Imports System.Globalization

Module Example

   Dim format As String = "{0,-20}{1,-20}{2}"

   ' Get the exception type name; remove the namespace prefix.
   Function GetExceptionType(ByVal ex As Exception) As String

      Dim exceptionType As String = ex.GetType().ToString()
      Return exceptionType.Substring( _
          exceptionType.LastIndexOf("."c) + 1)
   End Function

   Sub ConvertToByte(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal numericStr As String, _
       ByVal provider As IFormatProvider)

      Dim defaultValue As Object
      Dim providerValue As Object

      ' Convert numericStr to Byte without a format provider.
      Try
         defaultValue = Convert.ToByte(numericStr)
      Catch ex As Exception
         defaultValue = GetExceptionType(ex)
      End Try

      ' Convert numericStr to Byte with a format provider.
      Try
         providerValue = Convert.ToByte(numericStr, provider)
      Catch ex As Exception
         providerValue = GetExceptionType(ex)
      End Try

      outputBlock.Text &= String.Format(format, numericStr, _
          defaultValue, providerValue) & vbCrLf
   End Sub

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Create a NumberFormatInfo object and set several of its
      ' properties that apply to numbers.
      Dim provider As NumberFormatInfo = New NumberFormatInfo()

      ' These properties affect the conversion.
      provider.PositiveSign = "pos "
      provider.NegativeSign = "neg "

      ' These properties do not affect the conversion.
      ' The input string cannot have decimal and group separators.
      provider.NumberDecimalSeparator = "."

      outputBlock.Text &= String.Format("This example of" & vbCrLf & _
          "  Convert.ToByte( String ) and " & vbCrLf & _
          "  Convert.ToByte( String, IFormatProvider ) " & _
          vbCrLf & "generates the following output. It " & _
          "converts several strings to " & vbCrLf & "Byte " & _
          "values, using default formatting " & _
          "or a NumberFormatInfo object." & vbCrLf) & vbCrLf
      outputBlock.Text &= String.Format(format, "String to convert", _
          "Default/exception", "Provider/exception") & vbCrLf
      outputBlock.Text &= String.Format(format, "-----------------", _
          "-----------------", "------------------") & vbCrLf

      ' Convert strings, with and without an IFormatProvider.
      ConvertToByte(outputBlock, "234", provider)
      ConvertToByte(outputBlock, "+234", provider)
      ConvertToByte(outputBlock, "pos 234", provider)
      ConvertToByte(outputBlock, "234.", provider)
      ConvertToByte(outputBlock, "255", provider)
      ConvertToByte(outputBlock, "256", provider)
      ConvertToByte(outputBlock, "-1", provider)
   End Sub
End Module

' This example of
'   Convert.ToByte( String ) and
'   Convert.ToByte( String, IFormatProvider )
' generates the following output. It converts several strings to
' Byte values, using default formatting or a NumberFormatInfo object.
' 
' String to convert   Default/exception   Provider/exception
' -----------------   -----------------   ------------------
' 234                 234                 234
' +234                234                 FormatException
' pos 234             FormatException     234
' 234.                FormatException     FormatException
' 255                 255                 255
' 256                 OverflowException   OverflowException
' -1                  OverflowException   FormatException
// Example of the Convert.ToByte( string ) and 
// Convert.ToByte( string, IFormatProvider ) methods.
using System;
using System.Globalization;

class Example
{
   static string format = "{0,-20}{1,-20}{2}";

   // Get the exception type name; remove the namespace prefix.
   static string GetExceptionType(Exception ex)
   {
      string exceptionType = ex.GetType().ToString();
      return exceptionType.Substring(
          exceptionType.LastIndexOf('.') + 1);
   }

   static void ConvertToByte(System.Windows.Controls.TextBlock outputBlock, string numericStr,
       IFormatProvider provider)
   {
      object defaultValue;
      object providerValue;

      // Convert numericStr to Byte without a format provider.
      try
      {
         defaultValue = Convert.ToByte(numericStr);
      }
      catch (Exception ex)
      {
         defaultValue = GetExceptionType(ex);
      }

      // Convert numericStr to Byte with a format provider.
      try
      {
         providerValue = Convert.ToByte(numericStr, provider);
      }
      catch (Exception ex)
      {
         providerValue = GetExceptionType(ex);
      }

      outputBlock.Text += String.Format(format, numericStr,
          defaultValue, providerValue) + "\n";
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create a NumberFormatInfo object and set several of its
      // properties that apply to numbers.
      NumberFormatInfo provider = new NumberFormatInfo();

      // These properties affect the conversion.
      provider.NegativeSign = "neg ";
      provider.PositiveSign = "pos ";

      // These properties do not affect the conversion.
      // The input string cannot have decimal and group separators.
      provider.NumberDecimalSeparator = ".";

      outputBlock.Text += String.Format("This example of\n" +
          "  Convert.ToByte( string ) and \n" +
          "  Convert.ToByte( string, IFormatProvider ) " +
          "\ngenerates the following output. It converts " +
          "several strings to \nbyte values, using " +
          "default formatting or a NumberFormatInfo object.\n") + "\n";
      outputBlock.Text += String.Format(format, "String to convert",
          "Default/exception", "Provider/exception") + "\n";
      outputBlock.Text += String.Format(format, "-----------------",
          "-----------------", "------------------") + "\n";

      // Convert strings, with and without an IFormatProvider.
      ConvertToByte(outputBlock, "234", provider);
      ConvertToByte(outputBlock, "+234", provider);
      ConvertToByte(outputBlock, "pos 234", provider);
      ConvertToByte(outputBlock, "234.", provider);
      ConvertToByte(outputBlock, "255", provider);
      ConvertToByte(outputBlock, "256", provider);
      ConvertToByte(outputBlock, "-1", provider);
   }
}

/*
This example of
  Convert.ToByte( string ) and
  Convert.ToByte( string, IFormatProvider )
generates the following output. It converts several strings to
byte values, using default formatting or a NumberFormatInfo object.

String to convert   Default/exception   Provider/exception
-----------------   -----------------   ------------------
234                 234                 234
+234                234                 FormatException
pos 234             FormatException     234
234.                FormatException     FormatException
255                 255                 255
256                 OverflowException   OverflowException
-1                  OverflowException   FormatException
*/

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.