NameObjectCollectionsBase Class

1. 底層結構為hash table.
2. 元素為key/value pair.
3. 預設處理key的雜湊函數不分大小寫.
4. Key跟Value都可以為null.

Example

using System;
using System.Collections;
using System.Collections.Specialized;

public class MyCollection : NameObjectCollectionBase
{
// Creates an empty collection.
public MyCollection() {
}

// Adds elements from an IDictionary into the new collection.
public MyCollection( IDictionary d, Boolean bReadOnly ) {
foreach ( DictionaryEntry de in d ) {
this.BaseAdd( (String) de.Key, de.Value );
}
this.IsReadOnly = bReadOnly;
}

// Gets a key-and-value pair (DictionaryEntry) using an index.
public DictionaryEntry this[ int index ] {
get {
return ( new DictionaryEntry( 
this.BaseGetKey(index), this.BaseGet(index) ) );
}
}

// Gets or sets the value associated with the specified key.
public Object this[ String key ] {
get {
return( this.BaseGet( key ) );
}
set {
this.BaseSet( key, value );
}
}

// Gets a String array that contains all the keys in the collection.
public String[] AllKeys {
get {
return( this.BaseGetAllKeys() );
}
}

// Gets an Object array that contains all the values in the collection.
public Array AllValues {
get {
return( this.BaseGetAllValues() );
}
}

// Gets a String array that contains all the values in the collection.
public String[] AllStringValues {
get {
return( (String[]) this.BaseGetAllValues( typeof( string ) ));
}
}

// Gets a value indicating if the collection contains keys that are not null.
public Boolean HasKeys {
get {
return( this.BaseHasKeys() );
}
}

// Adds an entry to the collection.
public void Add( String key, Object value ) {
this.BaseAdd( key, value );
}

// Removes an entry with the specified key from the collection.
public void Remove( String key ) {
this.BaseRemove( key );
}

// Removes an entry in the specified index from the collection.
public void Remove( int index ) {
this.BaseRemoveAt( index );
}

// Clears all the elements in the collection.
public void Clear() {
this.BaseClear();
}

}

public class SamplesNameObjectCollectionBase {

public static void Main() {

// Creates and initializes a new MyCollection that is read-only.
IDictionary d = new ListDictionary();
d.Add( "red", "apple" );
d.Add( "yellow", "banana" );
d.Add( "green", "pear" );
MyCollection myROCol = new MyCollection( d, true );

// Tries to add a new item.
try {
myROCol.Add( "blue", "sky" );
}
catch ( NotSupportedException e ) {
Console.WriteLine( e.ToString() );
}

// Displays the keys and values of the MyCollection.
Console.WriteLine( "Read-Only Collection:" );
PrintKeysAndValues( myROCol );


// Creates and initializes an empty MyCollection that is writable.
MyCollection myRWCol = new MyCollection();

// Adds new items to the collection.
myRWCol.Add( "purple", "grape" );
myRWCol.Add( "orange", "tangerine" );
myRWCol.Add( "black", "berries" );
Console.WriteLine( "Writable Collection (after adding values):" );
PrintKeysAndValues( myRWCol );

// Changes the value of one element.
myRWCol["orange"] = "grapefruit";
Console.WriteLine( "Writable Collection (after changing one value):" );
PrintKeysAndValues( myRWCol );

// Removes one item from the collection.
myRWCol.Remove( "black" );
Console.WriteLine( "Writable Collection (after removing one value):" );
PrintKeysAndValues( myRWCol );

// Removes all elements from the collection.
myRWCol.Clear();
Console.WriteLine( "Writable Collection (after clearing the collection):" );
PrintKeysAndValues( myRWCol );

}

// Prints the indexes, keys, and values.
public static void PrintKeysAndValues( MyCollection myCol ) {
for ( int i = 0; i < myCol.Count; i++ ) {
Console.WriteLine( "[{0}] : {1}, {2}", i, myCol[i].Key, myCol[i].Value );
}
}

// Prints the keys and values using AllKeys.
public static void PrintKeysAndValues2( MyCollection myCol ) {
foreach ( String s in myCol.AllKeys ) {
Console.WriteLine( "{0}, {1}", s, myCol[s] );
}
}
}


/*
This code produces the following output.

System.NotSupportedException: Collection is read-only.
at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
at SamplesNameObjectCollectionBase.Main()
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
Writable Collection (after adding values):
[0] : purple, grape
[1] : orange, tangerine
[2] : black, berries
Writable Collection (after changing one value):
[0] : purple, grape
[1] : orange, grapefruit
[2] : black, berries
Writable Collection (after removing one value):
[0] : purple, grape
[1] : orange, grapefruit
Writable Collection (after clearing the collection):

*/