IsSurrogatePair Method (String, Int32)
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Char.IsSurrogatePair Method (String, Int32)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Indicates whether two adjacent Char objects at a specified position in a string form a surrogate pair.

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

'Declaration
Public Shared Function IsSurrogatePair ( _
	s As String, _
	index As Integer _
) As Boolean

Parameters

s
Type: System.String
A string.
index
Type: System.Int32
A position within s.

Return Value

Type: System.Boolean
true if the s parameter and the index parameter specify a pair of adjacent characters, and the numeric value of the character at position index ranges from U+D800 through U+DBFF, and the numeric value of the character at position index+1 ranges from U+DC00 through U+DFFF; otherwise, false.

ExceptionCondition
ArgumentNullException

s is Nothing.

ArgumentOutOfRangeException

index is not a position within s.

Ordinarily, a single character is represented by a single 16-bit Unicode code unit. UTF-16 encoding also supports surrogate pairs, which allow a single abstract character to be represented by two 16-bit code units. The first code unit, whose value can range from U+D800 to U+DBFF, is the high surrogate. The second code unit, whose value can range from U+DC00 to U+DFFF, is the low surrogate. Individual surrogate code units have no interpretation of their own. For more information about surrogates and the Unicode Standard, see the Unicode home page.

The following example demonstrates the IsSurrogatePair method.


' This example demonstrates the Char.IsSurrogatePair() method

Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim cHigh As Char = ChrW(&HD800)
      Dim cLow As Char = ChrW(&HDC00)
      Dim s1 = New [String](New Char() {"a"c, ChrW(&HD800), ChrW(&HDC00), "z"c})
      Dim divider As String = [String].Concat(vbCrLf, _
                                              New [String]("-"c, 70), _
                                              vbCrLf)

      outputBlock.Text &= vbCrLf
      outputBlock.Text &= String.Format("Hexadecimal code point of the character, cHigh: {0:X4}", AscW(cHigh)) & vbCrLf
      outputBlock.Text &= String.Format("Hexadecimal code point of the character, cLow:  {0:X4}", AscW(cLow)) & vbCrLf
      outputBlock.Text &= vbCrLf
      outputBlock.Text &= String.Format("Characters in string, s1: 'a', high surrogate, low surrogate, 'z'") & vbCrLf
      outputBlock.Text &= String.Format("Hexadecimal code points of the characters in string, s1: ") & vbCrLf
      Dim i As Integer
      For i = 0 To s1.Length - 1
         outputBlock.Text &= String.Format("s1({0}) = {1:X4} ", i, AscW(s1.Chars(i))) & vbCrLf
      Next i
      outputBlock.Text &= divider & vbCrLf

      outputBlock.Text &= "Is each of the following pairs of characters a surrogate pair?" & vbCrLf
      outputBlock.Text &= String.Format("C1) cHigh and cLow?  - {0}", [Char].IsSurrogatePair(cHigh, cLow)) & vbCrLf
      outputBlock.Text &= String.Format("C2) s1(0) and s1(1)? - {0}", [Char].IsSurrogatePair(s1, 0)) & vbCrLf
      outputBlock.Text &= String.Format("C3) s1(1) and s1(2)? - {0}", [Char].IsSurrogatePair(s1, 1)) & vbCrLf
      outputBlock.Text &= String.Format("C4) s1(2) and s1(3)? - {0}", [Char].IsSurrogatePair(s1, 2)) & vbCrLf
      outputBlock.Text &= divider & vbCrLf
   End Sub 'Main
End Class 'Sample
'
'This example produces the following results:
'
'Hexadecimal code point of the character, cHigh: D800
'Hexadecimal code point of the character, cLow:  DC00
'
'Characters in string, s1: 'a', high surrogate, low surrogate, 'z'
'Hexadecimal code points of the characters in string, s1:
's1(0) = 0061
's1(1) = D800
's1(2) = DC00
's1(3) = 007A
'
'----------------------------------------------------------------------
'
'Is each of the following pairs of characters a surrogate pair?
'C1) cHigh and cLow?  - True
'C2) s1(0) and s1(1)? - False
'C3) s1(1) and s1(2)? - True
'C4) s1(2) and s1(3)? - False
'
'----------------------------------------------------------------------


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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