Artikel
11/18/2011

Char Structure

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Updated: December 2010

Represents a Unicode character.

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Structure Char _
    Implements IComparable, IConvertible, IComparable(Of Char),  _
    IEquatable(Of Char)

[ComVisibleAttribute(true)]
public struct Char : IComparable, IConvertible, 
    IComparable<char>, IEquatable<char>

The Char type exposes the following members.

Methods

	Name	Description
	CompareTo(Char)	Compares this instance to a specified Char object and returns an integer that indicates whether this instance precedes, follows, or has the same position in the sort order as the specified Char value.
	CompareTo(Object)	Compares this instance to a specified object and returns an integer that indicates whether this instance precedes, follows, or has the same position in the sort order as the specified object.
	Equals(Char)	Returns a value indicating whether this instance is equal to the specified Char object.
	Equals(Object)	Returns a value indicating whether this instance is equal to a specified object. (Overrides ValueType.Equals(Object).)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Returns the hash code for this instance. (Overrides ValueType.GetHashCode().)
	GetNumericValue(Char)	Converts the specified numeric Unicode character to a double-precision floating point number.
	GetNumericValue(String, Int32)	Converts the numeric Unicode character at the specified position in a specified string to a double-precision floating point number.
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	GetTypeCode	Returns the TypeCode for value type Char.
	GetUnicodeCategory(Char)	Categorizes a specified Unicode character into a group identified by one of the UnicodeCategory values.
	GetUnicodeCategory(String, Int32)	Categorizes the character at the specified position in a specified string into a group identified by one of the UnicodeCategory values.
	IsControl(Char)	Indicates whether the specified Unicode character is categorized as a control character.
	IsControl(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a control character.
	IsDigit(Char)	Indicates whether the specified Unicode character is categorized as a decimal digit.
	IsDigit(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a decimal digit.
	IsLetter(Char)	Indicates whether the specified Unicode character is categorized as a Unicode letter.
	IsLetter(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a Unicode letter.
	IsLetterOrDigit(Char)	Indicates whether the specified Unicode character is categorized as a letter or a decimal digit.
	IsLetterOrDigit(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a letter or a decimal digit.
	IsLower(Char)	Indicates whether the specified Unicode character is categorized as a lowercase letter.
	IsLower(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a lowercase letter.
	IsNumber(Char)	Indicates whether the specified Unicode character is categorized as a number.
	IsNumber(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a number.
	IsPunctuation(Char)	Indicates whether the specified Unicode character is categorized as a punctuation mark.
	IsPunctuation(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a punctuation mark.
	IsSeparator(Char)	Indicates whether the specified Unicode character is categorized as a separator character.
	IsSeparator(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a separator character.
	IsSurrogate(Char)	Indicates whether the specified character has a surrogate code point.
	IsSurrogate(String, Int32)	Indicates whether the character at the specified position in a specified string has a surrogate code point.
	IsSurrogatePair(Char, Char)	Indicates whether the two specified Char objects form a surrogate pair.
	IsSurrogatePair(String, Int32)	Indicates whether two adjacent Char objects at a specified position in a string form a surrogate pair.
	IsSymbol(Char)	Indicates whether the specified Unicode character is categorized as a symbol character.
	IsSymbol(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a symbol character.
	IsUpper(Char)	Indicates whether the specified Unicode character is categorized as an uppercase letter.
	IsUpper(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as an uppercase letter.
	IsWhiteSpace(Char)	Indicates whether the specified Unicode character is categorized as white space.
	IsWhiteSpace(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as white space.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToLower(Char)	Converts the value of a Unicode character to its lowercase equivalent.
	ToLower(Char, CultureInfo)	Converts the value of a specified Unicode character to its lowercase equivalent using specified culture-specific formatting information.
	ToLowerInvariant	Converts the value of a Unicode character to its lowercase equivalent using the casing rules of the invariant culture.
	ToString()	Converts the value of this instance to its equivalent string representation. (Overrides ValueType.ToString().)
	ToString(Char)	Converts the specified Unicode character to its equivalent string representation.
	ToString(IFormatProvider)	Converts the value of this instance to its equivalent string representation using the specified culture-specific format information.
	ToUpper(Char)	Converts the value of a Unicode character to its uppercase equivalent.
	ToUpper(Char, CultureInfo)	Converts the value of a specified Unicode character to its uppercase equivalent using specified culture-specific formatting information.
	ToUpperInvariant	Converts the value of a Unicode character to its uppercase equivalent using the casing rules of the invariant culture.
	TryParse	Converts the value of the specified string to its equivalent Unicode character. A return code indicates whether the conversion succeeded or failed.

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Fields

	Name	Description
	MaxValue	Represents the largest possible value of a Char. This field is constant.
	MinValue	Represents the smallest possible value of a Char. This field is constant.

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Explicit Interface Implementations

	Name	Description
	IConvertible.ToBoolean	Infrastructure. Note This conversion is not supported. Attempting to do so throws an InvalidCastException.
	IConvertible.ToByte	Infrastructure. For a description of this member, see ToByte.
	IConvertible.ToChar	Infrastructure. For a description of this member, see IConvertible.ToChar.
	IConvertible.ToDateTime	Infrastructure. Note This conversion is not supported. Attempting to do so throws an InvalidCastException.
	IConvertible.ToDecimal	Infrastructure. Note This conversion is not supported. Attempting to do so throws an InvalidCastException.
	IConvertible.ToDouble	Infrastructure. Note This conversion is not supported. Attempting to do so throws an InvalidCastException.
	IConvertible.ToInt16	Infrastructure. For a description of this member, see ToInt16.
	IConvertible.ToInt32	Infrastructure. For a description of this member, see ToInt32.
	IConvertible.ToInt64	Infrastructure. For a description of this member, see ToInt64.
	IConvertible.ToSByte	Infrastructure. For a description of this member, see ToSByte.
	IConvertible.ToSingle	Infrastructure. Note This conversion is not supported. Attempting to do so throws an InvalidCastException.
	IConvertible.ToType	Infrastructure. For a description of this member, see IConvertible.ToType.
	IConvertible.ToUInt16	Infrastructure. For a description of this member, see ToUInt16.
	IConvertible.ToUInt32	Infrastructure. For a description of this member, see ToUInt32.
	IConvertible.ToUInt64	Infrastructure. For a description of this member, see ToUInt64.

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Remarks

The .NET Framework uses the Char structure to represent a Unicode character. The Unicode Standard identifies each Unicode character with a unique 21-bit scalar number called a code point, and defines the UTF-16 encoding form that specifies how a code point is encoded into a sequence of one or more 16-bit values. Each 16-bit value ranges from hexadecimal 0x0000 through 0xFFFF and is stored in a Char structure. The value of a Char object is its 16-bit numeric (ordinal) value.

Char Objects, Unicode Characters, and Strings

A String object is a sequential collection of Char structures that represents a string of text. Most Unicode characters can be represented by a single Char object, but a character that is encoded as a base character, surrogate pair, and/or combining character sequence is represented by multiple Char objects. For this reason, a Char structure in a String object is not necessarily equivalent to a single Unicode character.

Multiple 16-bit code points are used to represent single Unicode characters in the following cases:

Glyphs, which may consist of a single character or of a base character followed by one or more combining characters. For example, the character ä is represented by a Char object whose code point is U+0061 followed by a Char object whose code point is U+0308. (The character ä can also be defined by a single Char object that has a code point of U+00E4.) The following example illustrates that the character ä consists of two Char objects.

Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      Dim chars() As Char = {ChrW(&H61), ChrW(&H308)}
      Dim strng As New String(chars)
      outputBlock.Text += strng + vbCrLf
   End Sub
End Module
' The example produces the following output:
'       ä

using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      char[] chars = { '\u0061', '\u0308' };
      string strng = new String(chars);
      outputBlock.Text += strng + Environment.NewLine;
   }
}
// The example produces the following output:
//       ä

Characters outside the Unicode Basic Multilingual Plane (BMP). Unicode supports sixteen planes in addition to the BMP, which represents plane 0. A Unicode code point is represented in UTF-32 by a 21-bit value that includes the plane. For example, U+1D160 represents the MUSICAL SYMBOL EIGHTH NOTE character. Because UTF-16 encoding has only 16 bits, characters outside the BMP are represented by surrogate pairs in UTF-16. For example, the UTF-16 equivalent of U+1D160, the MUSICAL SYMBOL EIGHTH NOTE character, is U+D834 U+DD60. U+D834 is the high surrogate; high surrogates range from U+D800 through U+DBFF. U+DD60 is the low surrogate; low surrogates range from U+DC00 through U+DFFF.

Because a single character can be represented by multiple Char objects, we recommend that you use strings instead of individual characters to represent and analyze linguistic content.

Functionality

The Char structure provides methods to compare Char objects, convert the value of the current Char object to an object of another type, and determine the Unicode category of a Char object:

Use the CompareTo and Equals methods to compare Char objects.
Use the GetUnicodeCategory methods to get the Unicode category of a character. Use the IsControl, IsDigit, IsLetter, IsLetterOrDigit, IsLower, IsNumber, IsPunctuation, IsSeparator, IsSurrogate, IsSurrogatePair, IsSymbol, IsUpper, and IsWhiteSpace methods to determine whether a character is in a particular Unicode category such as digit, letter, punctuation, control character, and so on.
Use the GetNumericValue methods to convert a Char object that represents a number to a numeric value type. Use TryParse to convert a character in a string into a Char object. Use ToString to convert a Char object to a String object.
Use the ToLower and ToUpper methods to change the case of a Char object.

Interface Implementations

This type implements the IConvertible, IComparable, and IComparable<T> interfaces. Use the Convert class for conversions instead of this type's explicit interface member implementation of IConvertible.

Examples

The following example demonstrates some of the methods in Char.

Module Example

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim chA As Char = "A"c
      Dim ch1 As Char = "1"c
      Dim str As String = "test string"

      outputBlock.Text &= chA.CompareTo("B"c)                   ' Output: "-1" (meaning 'A' is 1 less than 'B' & vbCrLf
      outputBlock.Text &= chA.Equals("A"c) & vbCrLf             ' Output: "True"
      outputBlock.Text &= Char.GetNumericValue(ch1) & vbCrLf    ' Output: "1"
      outputBlock.Text &= Char.IsControl(ChrW(9)) & vbCrLf      ' Output: "True"
      outputBlock.Text &= Char.IsDigit(ch1) & vbCrLf            ' Output: "True"
      outputBlock.Text += Char.IsLetter(","c) & vbCrLf          ' Output: "False"
      outputBlock.Text &= Char.IsLower("u"c) & vbCrLf           ' Output: "True"
      outputBlock.Text &= Char.IsNumber(ch1) & vbCrLf           ' Output: "True"
      outputBlock.Text &= Char.IsPunctuation("."c) & vbCrLf     ' Output: "True"
      outputBlock.Text += Char.IsSeparator(str, 4) & vbCrLf     ' Output: "True"
      outputBlock.Text &= Char.IsSymbol("+"c) & vbCrLf          ' Output: "True"
      outputBlock.Text += Char.IsWhiteSpace(str, 4) & vbCrLf    ' Output: "True"
      outputBlock.Text &= Char.ToLower("M"c) & vbCrLf           ' Output: "m"
      outputBlock.Text &= "x"c.ToString() & vbCrLf              ' Output: "x"
   End Sub
End Module

using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      char chA = 'A';
      char ch1 = '1';
      string str = "test string";

      outputBlock.Text += chA.CompareTo('B') + "\n";            // Output: "-1" (meaning 'A' is 1 less than 'B')
      outputBlock.Text += chA.Equals('A') + "\n";               // Output: "True"
      outputBlock.Text += Char.GetNumericValue(ch1) + "\n"; // Output: "1"
      outputBlock.Text += Char.IsControl('\t') + "\n";      // Output: "True"
      outputBlock.Text += Char.IsDigit(ch1) + "\n";         // Output: "True"
      outputBlock.Text += Char.IsLetter(',') + "\n";            // Output: "False"
      outputBlock.Text += Char.IsLower('u') + "\n";         // Output: "True"
      outputBlock.Text += Char.IsNumber(ch1) + "\n";            // Output: "True"
      outputBlock.Text += Char.IsPunctuation('.') + "\n";   // Output: "True"
      outputBlock.Text += Char.IsSeparator(str, 4) + "\n";  // Output: "True"
      outputBlock.Text += Char.IsSymbol('+') + "\n";            // Output: "True"
      outputBlock.Text += Char.IsWhiteSpace(str, 4) + "\n"; // Output: "True"
      outputBlock.Text += Char.ToLower('M') + "\n";         // Output: "m"
      outputBlock.Text += 'x'.ToString() + "\n";                // Output: "x"
   }
}

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.

Thread Safety

All members of this type are thread safe. Members that appear to modify instance state actually return a new instance initialized with the new value. As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.

Change History

Date	History	Reason
December 2010	Provided additional information about the difference between a Char object and a Unicode character.	Information enhancement.

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