CharEnumerator Class
Supports iterating over a String object and reading its individual characters. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
The CharEnumerator type exposes the following members.
| Name | Description | |
|---|---|---|
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Clone | Creates a copy of the current CharEnumerator object. |
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Dispose | Releases all resources used by the current instance of the CharEnumerator class. |
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Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
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Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
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GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
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GetType | Gets the Type of the current instance. (Inherited from Object.) |
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MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
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MoveNext | Increments the internal index of the current CharEnumerator object to the next character of the enumerated string. |
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Reset | Initializes the index to a position logically before the first character of the enumerated string. |
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ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
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IDisposable.Dispose | Releases all resources used by the CharEnumerator class. |
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IEnumerator.Current | Infrastructure. Gets the currently referenced character in the string enumerated by this CharEnumerator object. For a description of this member, see IEnumerator.Current. |
A CharEnumerator provides read-only access to the characters in a referenced String object. For example, the foreach statement of the Microsoft Visual Basic and C# programming languages, which iterates through the elements of a collection, retrieves a CharEnumerator from a String object in order to iterate through the characters in that object.
There is no public constructor for CharEnumerator. Instead, call a String object's GetEnumerator method to obtain a CharEnumerator that is initialized to reference the string.
A CharEnumerator maintains an internal index to the characters in the string the CharEnumerator references. The state of the index is invalid when it references a character position logically before the first character or after the last character in the string, and valid when it references a character within the string. The index is initialized to a position logically before the first character, and is set to a position after the last character when the iteration is complete. An exception is thrown if you attempt to access a character while the index is invalid.
The MoveNext method increments the index by one, so the first and subsequent characters are accessed in turn. The Reset method sets the index to a position logically before the first character. The Current property retrieves the character currently referenced by index. The Clone method creates a copy of the CharEnumerator.
Note
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Several independent instances of CharEnumerator across one or more threads can have access to a single instance of String. This class is implemented to support the IEnumerator interface. For more information regarding the use of an enumerator, see the IEnumerator topic. |
The following example uses the CharEnumerator class to enumerate the individual characters in a string. It instantiates a CharEnumerator object by calling the String.GetEnumerator method, moves from one character to the next by calling the MoveNext method, and displays the current character by retrieving the value of the Current property.
string title = "A Tale of Two Cities"; CharEnumerator chEnum = title.GetEnumerator(); int ctr = 1; string outputLine1 = null; string outputLine2 = null; string outputLine3 = null; while (chEnum.MoveNext()) { outputLine1 += ctr < 10 || ctr % 10 != 0 ? " " : (ctr / 10) + " "; outputLine2 += (ctr % 10) + " "; outputLine3 += chEnum.Current + " "; ctr++; } Console.WriteLine("The length of the string is {0} characters:", title.Length); Console.WriteLine(outputLine1); Console.WriteLine(outputLine2); Console.WriteLine(outputLine3); // The example displays the following output to the console: // The length of the string is 20 characters: // 1 2 // 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 // A T a l e o f T w o C i t i e s
Note, however, that the same operation can be performed somewhat more intuitively by using foreach (in C#) or For Each (in Visual Basic), as the following example shows.
string title = "A Tale of Two Cities"; int ctr = 1; string outputLine1 = null; string outputLine2 = null; string outputLine3 = null; foreach (char ch in title) { outputLine1 += ctr < 10 || ctr % 10 != 0 ? " " : (ctr / 10) + " "; outputLine2 += (ctr % 10) + " "; outputLine3 += ch + " "; ctr++; } Console.WriteLine("The length of the string is {0} characters:", title.Length); Console.WriteLine(outputLine1); Console.WriteLine(outputLine2); Console.WriteLine(outputLine3); // The example displays the following output to the console: // The length of the string is 20 characters: // 1 2 // 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 // A T a l e o f T w o C i t i e s
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Consulting source code, Object IEnumerator.Current is the ONLY member with explicit interface implementation. Other members of respective interfaces are implicit implementation.
Explicit Interface Implementation (C# Programming Guide)
- http://msdn.microsoft.com/en-us/library/ms173157.aspx
Implicit and Explicit Interface Implementations
- http://blogs.msdn.com/b/mhop/archive/2006/12/12/implicit-and-explicit-interface-implementations.aspx
Design Guideline Update: Explicit Member Implementation
- http://blogs.msdn.com/b/brada/archive/2003/11/15/50721.aspx
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*============================================================
**
** Class: CharEnumerator
**
**
** Purpose: Enumerates the characters on a string. skips range
** checks.
**
**
============================================================*/
namespace System {
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
[System.Runtime.InteropServices.ComVisible(true)]
[Serializable]
public sealed class CharEnumerator : IEnumerator, ICloneable, IEnumerator<char>, IDisposable {
private String str;
private int index;
private char currentElement;
internal CharEnumerator(String str) {
Contract.Requires(str != null);
this.str = str;
this.index = -1;
}
[System.Security.SecuritySafeCritical] // auto-generated
public Object Clone() {
return MemberwiseClone();
}
public bool MoveNext() {
if (index < (str.Length-1)) {
index++;
currentElement = str[index];
return true;
}
else
index = str.Length;
return false;
}
public void Dispose() {
if (str != null)
index = str.Length;
str = null;
}
/// <internalonly/>
Object IEnumerator.Current {
get {
if (index == -1)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
if (index >= str.Length)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
return currentElement;
}
}
public char Current {
get {
if (index == -1)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
if (index >= str.Length)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
return currentElement;
}
}
public void Reset() {
currentElement = (char)0;
index = -1;
}
}
}
// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*============================================================
**
** Class: CharEnumerator
**
**
** Purpose: Enumerates the characters on a string. skips range
** checks.
**
**
============================================================*/
namespace System {
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
[System.Runtime.InteropServices.ComVisible(true)]
[Serializable]
public sealed class CharEnumerator : IEnumerator, ICloneable, IEnumerator<char>, IDisposable {
private String str;
private int index;
private char currentElement;
internal CharEnumerator(String str) {
Contract.Requires(str != null);
this.str = str;
this.index = -1;
}
[System.Security.SecuritySafeCritical] // auto-generated
public Object Clone() {
return MemberwiseClone();
}
public bool MoveNext() {
if (index < (str.Length-1)) {
index++;
currentElement = str[index];
return true;
}
else
index = str.Length;
return false;
}
public void Dispose() {
if (str != null)
index = str.Length;
str = null;
}
/// <internalonly/>
Object IEnumerator.Current {
get {
if (index == -1)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
if (index >= str.Length)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
return currentElement;
}
}
public char Current {
get {
if (index == -1)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
if (index >= str.Length)
throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
return currentElement;
}
}
public void Reset() {
currentElement = (char)0;
index = -1;
}
}
}
// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
- 3/17/2011
- RogerVillela
