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Char.IsLowSurrogate Method (Char)

Indicates whether the specified Char object is a low surrogate.

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

'Declaration
Public Shared Function IsLowSurrogate ( _
	c As Char _
) As Boolean

Parameters

c
Type: System.Char

The character to evaluate.

Return Value

Type: System.Boolean
true if the numeric value of the c parameter ranges from U+DC00 through U+DFFF; otherwise, false.

In addition to representing single characters using a 16-bit code point, UTF-16 encoding allows abstract characters to be represented using two 16-bit code points, which is known as a surrogate pair. The second element in this pair is the low surrogate. Its code point can range from U+DC00 to U+DFFF. An individual surrogate has no interpretation of its own; it is meaningful only when used as part of a surrogate pair.

The following code example demonstrates the IsHighSurrogate, IsLowSurrogate, and IsSurrogatePair methods.

' This example demonstrates the Char.IsLowSurrogate() method 
'                                    IsHighSurrogate() method 
'                                    IsSurrogatePair() method 
Imports System
Imports Microsoft.VisualBasic

Class Sample
   Public Shared Sub Main()
      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(Environment.NewLine, _
                                              New [String]("-"c, 70), _
                                              Environment.NewLine)

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

      Console.WriteLine("Is each of the following characters a high surrogate?")
      Console.WriteLine("A1) cLow?  - {0}", [Char].IsHighSurrogate(cLow))
      Console.WriteLine("A2) cHigh? - {0}", [Char].IsHighSurrogate(cHigh))
      Console.WriteLine("A3) s1(0)? - {0}", [Char].IsHighSurrogate(s1, 0))
      Console.WriteLine("A4) s1(1)? - {0}", [Char].IsHighSurrogate(s1, 1))
      Console.WriteLine(divider)

      Console.WriteLine("Is each of the following characters a low surrogate?")
      Console.WriteLine("B1) cLow?  - {0}", [Char].IsLowSurrogate(cLow))
      Console.WriteLine("B2) cHigh? - {0}", [Char].IsLowSurrogate(cHigh))
      Console.WriteLine("B3) s1(0)? - {0}", [Char].IsLowSurrogate(s1, 0))
      Console.WriteLine("B4) s1(2)? - {0}", [Char].IsLowSurrogate(s1, 2))
      Console.WriteLine(divider)

      Console.WriteLine("Is each of the following pairs of characters a surrogate pair?")
      Console.WriteLine("C1) cHigh and cLow?  - {0}", [Char].IsSurrogatePair(cHigh, cLow))
      Console.WriteLine("C2) s1(0) and s1(1)? - {0}", [Char].IsSurrogatePair(s1, 0))
      Console.WriteLine("C3) s1(1) and s1(2)? - {0}", [Char].IsSurrogatePair(s1, 1))
      Console.WriteLine("C4) s1(2) and s1(3)? - {0}", [Char].IsSurrogatePair(s1, 2))
      Console.WriteLine(divider)
   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 characters a high surrogate? 
'A1) cLow?  - False 
'A2) cHigh? - True 
'A3) s1(0)? - False 
'A4) s1(1)? - True 

'---------------------------------------------------------------------- 

'Is each of the following characters a low surrogate? 
'B1) cLow?  - True 
'B2) cHigh? - False 
'B3) s1(0)? - False 
'B4) s1(2)? - True 

'---------------------------------------------------------------------- 

'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 

'---------------------------------------------------------------------- 
'

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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