DictionaryBase Class
Assembly: mscorlib (in mscorlib.dll)
[SerializableAttribute] [ComVisibleAttribute(true)] public abstract class DictionaryBase : IDictionary, ICollection, IEnumerable
/** @attribute SerializableAttribute() */ /** @attribute ComVisibleAttribute(true) */ public abstract class DictionaryBase implements IDictionary, ICollection, IEnumerable
SerializableAttribute ComVisibleAttribute(true) public abstract class DictionaryBase implements IDictionary, ICollection, IEnumerable
Not applicable.
The foreach statement of the C# language (for each in Visual Basic) requires the type of each element in the collection. Since each element of the DictionaryBase is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is DictionaryEntry. For example:
The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.
Note: |
|---|
| Because keys can be inherited and their behavior changed, their absolute uniqueness cannot be guaranteed by comparisons using the Equals method. |
The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.
using System; using System.Collections; public class ShortStringDictionary : DictionaryBase { public String this[ String key ] { get { return( (String) Dictionary[key] ); } set { Dictionary[key] = value; } } public ICollection Keys { get { return( Dictionary.Keys ); } } public ICollection Values { get { return( Dictionary.Values ); } } public void Add( String key, String value ) { Dictionary.Add( key, value ); } public bool Contains( String key ) { return( Dictionary.Contains( key ) ); } public void Remove( String key ) { Dictionary.Remove( key ); } protected override void OnInsert( Object key, Object value ) { if ( key.GetType() != typeof(System.String) ) throw new ArgumentException( "key must be of type String.", "key" ); else { String strKey = (String) key; if ( strKey.Length > 5 ) throw new ArgumentException( "key must be no more than 5 characters in length.", "key" ); } if ( value.GetType() != typeof(System.String) ) throw new ArgumentException( "value must be of type String.", "value" ); else { String strValue = (String) value; if ( strValue.Length > 5 ) throw new ArgumentException( "value must be no more than 5 characters in length.", "value" ); } } protected override void OnRemove( Object key, Object value ) { if ( key.GetType() != typeof(System.String) ) throw new ArgumentException( "key must be of type String.", "key" ); else { String strKey = (String) key; if ( strKey.Length > 5 ) throw new ArgumentException( "key must be no more than 5 characters in length.", "key" ); } } protected override void OnSet( Object key, Object oldValue, Object newValue ) { if ( key.GetType() != typeof(System.String) ) throw new ArgumentException( "key must be of type String.", "key" ); else { String strKey = (String) key; if ( strKey.Length > 5 ) throw new ArgumentException( "key must be no more than 5 characters in length.", "key" ); } if ( newValue.GetType() != typeof(System.String) ) throw new ArgumentException( "newValue must be of type String.", "newValue" ); else { String strValue = (String) newValue; if ( strValue.Length > 5 ) throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" ); } } protected override void OnValidate( Object key, Object value ) { if ( key.GetType() != typeof(System.String) ) throw new ArgumentException( "key must be of type String.", "key" ); else { String strKey = (String) key; if ( strKey.Length > 5 ) throw new ArgumentException( "key must be no more than 5 characters in length.", "key" ); } if ( value.GetType() != typeof(System.String) ) throw new ArgumentException( "value must be of type String.", "value" ); else { String strValue = (String) value; if ( strValue.Length > 5 ) throw new ArgumentException( "value must be no more than 5 characters in length.", "value" ); } } } public class SamplesDictionaryBase { public static void Main() { // Creates and initializes a new DictionaryBase. ShortStringDictionary mySSC = new ShortStringDictionary(); // Adds elements to the collection. mySSC.Add( "One", "a" ); mySSC.Add( "Two", "ab" ); mySSC.Add( "Three", "abc" ); mySSC.Add( "Four", "abcd" ); mySSC.Add( "Five", "abcde" ); // Display the contents of the collection using foreach. This is the preferred method. Console.WriteLine( "Contents of the collection (using foreach):" ); PrintKeysAndValues1( mySSC ); // Display the contents of the collection using the enumerator. Console.WriteLine( "Contents of the collection (using enumerator):" ); PrintKeysAndValues2( mySSC ); // Display the contents of the collection using the Keys property and the Item property. Console.WriteLine( "Initial contents of the collection (using Keys and Item):" ); PrintKeysAndValues3( mySSC ); // Tries to add a value that is too long. try { mySSC.Add( "Ten", "abcdefghij" ); } catch ( ArgumentException e ) { Console.WriteLine( e.ToString() ); } // Tries to add a key that is too long. try { mySSC.Add( "Eleven", "ijk" ); } catch ( ArgumentException e ) { Console.WriteLine( e.ToString() ); } Console.WriteLine(); // Searches the collection with Contains. Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) ); Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) ); Console.WriteLine(); // Removes an element from the collection. mySSC.Remove( "Two" ); // Displays the contents of the collection. Console.WriteLine( "After removing \"Two\":" ); PrintKeysAndValues1( mySSC ); } // Uses the foreach statement which hides the complexity of the enumerator. // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection. public static void PrintKeysAndValues1( ShortStringDictionary myCol ) { foreach ( DictionaryEntry myDE in myCol ) Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value ); Console.WriteLine(); } // Uses the enumerator. // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection. public static void PrintKeysAndValues2( ShortStringDictionary myCol ) { DictionaryEntry myDE; System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator(); while ( myEnumerator.MoveNext() ) if ( myEnumerator.Current != null ) { myDE = (DictionaryEntry) myEnumerator.Current; Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value ); } Console.WriteLine(); } // Uses the Keys property and the Item property. public static void PrintKeysAndValues3( ShortStringDictionary myCol ) { ICollection myKeys = myCol.Keys; foreach ( String k in myKeys ) Console.WriteLine( " {0,-5} : {1}", k, myCol[k] ); Console.WriteLine(); } } /* This code produces the following output. Contents of the collection (using foreach): Three : abc Five : abcde Two : ab One : a Four : abcd Contents of the collection (using enumerator): Three : abc Five : abcde Two : ab One : a Four : abcd Initial contents of the collection (using Keys and Item): Three : abc Five : abcde Two : ab One : a Four : abcd System.ArgumentException: value must be no more than 5 characters in length. Parameter name: value at ShortStringDictionary.OnValidate(Object key, Object value) at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value) at SamplesDictionaryBase.Main() System.ArgumentException: key must be no more than 5 characters in length. Parameter name: key at ShortStringDictionary.OnValidate(Object key, Object value) at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value) at SamplesDictionaryBase.Main() Contains "Three": True Contains "Twelve": False After removing "Two": Three : abc Five : abcde One : a Four : abcd */
import System.*;
import System.Collections.*;
public class ShortStringDictionary extends DictionaryBase
{
/** @property
*/
public String get_Value(String key)
{
return((String)(get_Dictionary().get_Item(key)));
} //get_Value
/** @property
*/
public void set_Value(String key,String value)
{
get_Dictionary().set_Item(key, value);
} //set_Value
/** @property
*/
public ICollection get_Keys()
{
return get_Dictionary().get_Keys();
} //get_Keys
/** @property
*/
public ICollection get_Values()
{
return get_Dictionary().get_Values();
} //get_Values
public void Add(String key, String value)
{
get_Dictionary().Add(key, value);
} //Add
public boolean Contains(String key)
{
return get_Dictionary().Contains(key);
} //Contains
public void Remove(String key)
{
get_Dictionary().Remove(key);
} //Remove
protected void OnInsert(Object key, Object value)
{
if (!key.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("key must be of type String.", "key");
}
else {
String strKey = ((String)(key));
if (strKey.length() > 5) {
throw new ArgumentException("key must be no more than "
+ "5 characters in length.", "key");
}
}
if (!value.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("value must be of type String.",
"value");
}
else {
String strValue = (String)value;
if (strValue.length() > 5) {
throw new ArgumentException("value must be no more than "
+ "5 characters in length.", "value");
}
}
} //OnInsert
protected void OnRemove(Object key, Object value)
{
if (!key.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("key must be of type String.", "key");
}
else {
String strKey = ((String)(key));
if (strKey.length() > 5) {
throw new ArgumentException("key must be no more than "
+ "5 characters in length.", "key");
}
}
} //OnRemove
protected void OnSet(Object key, Object oldValue, Object newValue)
{
if (!key.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("key must be of type String.", "key");
}
else {
String strKey = (String)key;
if (strKey.length() > 5) {
throw new ArgumentException("key must be no more than "
+ "5 characters in length.", "key") ;
}
}
if (!newValue.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("newValue must be of type String.",
"newValue") ;
}
else {
String strValue = ((String)(newValue));
if (strValue.length() > 5) {
throw new ArgumentException("newValue must be no more than "
+ "5 characters in length.", "newValue") ;
}
}
} //OnSet
protected void OnValidate(Object key, Object value)
{
if (!key.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("key must be of type String.", "key");
}
else {
String strKey = ((String)(key));
if (strKey.length() > 5) {
throw new ArgumentException("key must be no more than "
+ "5 characters in length.", "key") ;
}
}
if (!value.GetType().Equals(Type.GetType("System.String"))) {
throw new ArgumentException("value must be of type String.",
"value");
}
else {
String strValue = ((String)(value));
if (strValue.length() > 5) {
throw new ArgumentException("value must be no more than "
+ "5 characters in length.", "value") ;
}
}
} //OnValidate
} //ShortStringDictionary
public class SamplesDictionaryBase
{
public static void main(String[] args)
{
// Creates and initializes a new DictionaryBase.
ShortStringDictionary mySSC = new ShortStringDictionary();
// Adds elements to the collection.
mySSC.Add("One", "a");
mySSC.Add("Two", "ab");
mySSC.Add("Three", "abc");
mySSC.Add("Four", "abcd");
mySSC.Add("Five", "abcde");
// Display the contents of the collection using while. This is the
// preferred method.
Console.WriteLine("Contents of the collection (using for):");
PrintKeysAndValues1(mySSC);
// Display the contents of the collection using the enumerator.
Console.WriteLine("Contents of the collection (using enumerator):");
PrintKeysAndValues2(mySSC);
// Display the contents of the collection using the Keys property and
// the Item property.
Console.WriteLine("Initial contents of the collection (using Keys"
+ " and Item):");
PrintKeysAndValues3(mySSC);
// Tries to add a value that is too long.
try {
mySSC.Add("Ten", "abcdefghij");
}
catch(ArgumentException e) {
Console.WriteLine(e.ToString());
}
// Tries to add a key that is too long.
try {
mySSC.Add("Eleven", "ijk");
}
catch(ArgumentException e) {
Console.WriteLine(e.ToString());
}
Console.WriteLine();
// Searches the collection with Contains.
boolean b = mySSC.Contains("Three");
Console.Write("Contains \"Three\": ");
Console.WriteLine(b);
b = mySSC.Contains("Twelve");
Console.Write("Contains \"Twelve\": ");
Console.WriteLine(b);
Console.WriteLine();
// Removes an element from the collection.
mySSC.Remove("Two");
// Displays the contents of the collection.
Console.WriteLine("After removing \"Two\":");
PrintKeysAndValues1(mySSC);
}//main
// Uses the for statement which hides the complexity of the enumerator.
// NOTE: The for statement is the preferred way of enumerating the
// contents of a collection.
public static void PrintKeysAndValues1(ShortStringDictionary myCol)
{
String strValue;
String strKeys[] = new String[myCol.get_Count()];
myCol.get_Keys().CopyTo(strKeys,0);
for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++){
strValue = myCol.get_Value(strKeys[iCtr]);
Console.WriteLine(" {0,-5} : {1}", strKeys[iCtr], strValue);
}
Console.WriteLine();
} //PrintKeysAndValues1
// Uses the enumerator.
// NOTE: The for statement is the preferred way of enumerating the
// contents of a collection.
public static void PrintKeysAndValues2(ShortStringDictionary myCol)
{
DictionaryEntry myDE;
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while(myEnumerator.MoveNext()) {
if ( myEnumerator.get_Current() != null ) {
myDE =((DictionaryEntry)(myEnumerator.get_Current()));
Console.WriteLine(" {0,-5} : {1}", myDE.get_Key(),
myDE.get_Value());
}
}
Console.WriteLine();
} //PrintKeysAndValues2
// Uses the Keys property and the Value property.
public static void PrintKeysAndValues3(ShortStringDictionary myCol)
{
ICollection myKeys = myCol.get_Keys();
IEnumerator myEnumerator = myKeys.GetEnumerator();
while (myEnumerator.MoveNext()) {
String k = myEnumerator.get_Current().ToString();
Console.WriteLine(" {0,-5} : {1}", k, myCol.get_Item(k));
}
Console.WriteLine();
} //PrintKeysAndValues3
} //SamplesDictionaryBase
/*
This code produces the following output.
Contents of the collection (using while):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Contents of the collection (using enumerator):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Initial contents of the collection (using Keys and Item):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(
Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(
Object key, Object value)
at SamplesDictionaryBase.Main()
Contains "Three": True
Contains "Twelve": False
After removing "Two":
Three : abc
Five : abcde
One : a
Four : abcd
*/
Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
This implementation does not provide a synchronized (thread-safe) wrapper for a DictionaryBase, but derived classes can create their own synchronized versions of the DictionaryBase using the SyncRoot property.
Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.
Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.
Note: