DictionaryBase 类
为键/值对的强类型集合提供 abstract 基类。
**命名空间:**System.Collections
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class DictionaryBase
Implements IDictionary, ICollection, IEnumerable
用法
Dim instance As DictionaryBase
[SerializableAttribute]
[ComVisibleAttribute(true)]
public abstract class DictionaryBase : IDictionary, ICollection, IEnumerable
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class DictionaryBase abstract : 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
备注
C# 语言中的 foreach 语句（在 Visual Basic 中为 for each）需要集合中每个元素的类型。由于 DictionaryBase 的每个元素都是一个键/值对，因此元素类型既不是键的类型，也不是值的类型。而是 DictionaryEntry 类型。例如：
foreach (DictionaryEntry de in myDictionary) {...}
For Each de As Dictionary Entry In myDictionary
...
Next myDE
foreach 语句是对枚举数的包装，它只允许从集合中读取，不允许写入集合。
给实现者的说明 提供此基类旨在使实施者创建强类型自定义集合变得更容易。实现者最好扩展此基类，而不是创建自己的类。 此基类的成员受保护并且只能通过派生类使用。
示例
下面的代码示例实现 DictionaryBase 类，并使用该实现创建 Length 小于或等于 5 个字符的 String 键和值的字典。
Imports System
Imports System.Collections
Public Class ShortStringDictionary
Inherits DictionaryBase
Default Public Property Item(key As String) As String
Get
Return CType(Dictionary(key), String)
End Get
Set
Dictionary(key) = value
End Set
End Property
Public ReadOnly Property Keys() As ICollection
Get
Return Dictionary.Keys
End Get
End Property
Public ReadOnly Property Values() As ICollection
Get
Return Dictionary.Values
End Get
End Property
Public Sub Add(key As String, value As String)
Dictionary.Add(key, value)
End Sub 'Add
Public Function Contains(key As String) As Boolean
Return Dictionary.Contains(key)
End Function 'Contains
Public Sub Remove(key As String)
Dictionary.Remove(key)
End Sub 'Remove
Protected Overrides Sub OnInsert(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub 'OnInsert
Protected Overrides Sub OnRemove(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
End Sub 'OnRemove
Protected Overrides Sub OnSet(key As Object, oldValue As Object, newValue As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(newValue.GetType()) Then
Throw New ArgumentException("newValue must be of type String.", "newValue")
Else
Dim strValue As String = CType(newValue, String)
If strValue.Length > 5 Then
Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
End If
End If
End Sub 'OnSet
Protected Overrides Sub OnValidate(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub 'OnValidate
End Class 'ShortStringDictionary
Public Class SamplesDictionaryBase
Public Shared Sub Main()
' Creates and initializes a new DictionaryBase.
Dim mySSC As 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 For Each. This is the preferred method.
Console.WriteLine("Contents of the collection (using For Each):")
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 e As ArgumentException
Console.WriteLine(e.ToString())
End Try
' Tries to add a key that is too long.
Try
mySSC.Add("Eleven", "ijk")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
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)
End Sub 'Main
' Uses the For Each statement which hides the complexity of the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues1(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
For Each myDE In myCol
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
Next myDE
Console.WriteLine()
End Sub 'PrintKeysAndValues1
' Uses the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
If Not (myEnumerator.Current Is Nothing) Then
myDE = CType(myEnumerator.Current, DictionaryEntry)
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
End If
End While
Console.WriteLine()
End Sub 'PrintKeysAndValues2
' Uses the Keys property and the Item property.
Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
Dim myKeys As ICollection = myCol.Keys
Dim k As String
For Each k In myKeys
Console.WriteLine(" {0,-5} : {1}", k, myCol(k))
Next k
Console.WriteLine()
End Sub 'PrintKeysAndValues3
End Class 'SamplesDictionaryBase
'This code produces the following output.
'
'Contents of the collection (using For Each):
' 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
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
*/
using namespace System;
using namespace System::Collections;
public ref class ShortStringDictionary: public DictionaryBase
{
public:
property String^ Item [String^]
{
String^ get( String^ key )
{
return (dynamic_cast<String^>(Dictionary[ key ]));
}
void set( String^ value, String^ key )
{
Dictionary[ key ] = value;
}
}
property ICollection^ Keys
{
ICollection^ get()
{
return (Dictionary->Keys);
}
}
property ICollection^ Values
{
ICollection^ get()
{
return (Dictionary->Values);
}
}
void Add( String^ key, String^ value )
{
Dictionary->Add( key, value );
}
bool Contains( String^ key )
{
return (Dictionary->Contains( key ));
}
void Remove( String^ key )
{
Dictionary->Remove( key );
}
protected:
virtual void OnInsert( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
virtual void OnRemove( Object^ key, Object^ /*value*/ ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
}
virtual void OnSet( Object^ key, Object^ /*oldValue*/, Object^ newValue ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( newValue->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "newValue must be of type String.","newValue" );
else
{
String^ strValue = dynamic_cast<String^>(newValue);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "newValue must be no more than 5 characters in length.","newValue" );
}
}
virtual void OnValidate( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
};
void PrintKeysAndValues2( ShortStringDictionary^ myCol );
void PrintKeysAndValues3( ShortStringDictionary^ myCol );
int main()
{
// Creates and initializes a new DictionaryBase.
ShortStringDictionary^ mySSC = gcnew 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 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 );
}
// Tries to add a key that is too long.
try
{
mySSC->Add( "Eleven", "ijk" );
}
catch ( ArgumentException^ e )
{
Console::WriteLine( e );
}
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\":" );
PrintKeysAndValues2( mySSC );
}
// Uses the enumerator.
void PrintKeysAndValues2( ShortStringDictionary^ myCol )
{
DictionaryEntry myDE;
System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
while ( myEnumerator->MoveNext() )
if ( myEnumerator->Current != nullptr )
{
myDE = *dynamic_cast<DictionaryEntry^>(myEnumerator->Current);
Console::WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console::WriteLine();
}
// Uses the Keys property and the Item property.
void PrintKeysAndValues3( ShortStringDictionary^ myCol )
{
ICollection^ myKeys = myCol->Keys;
IEnumerator^ myEnum1 = myKeys->GetEnumerator();
while ( myEnum1->MoveNext() )
{
String^ k = safe_cast<String^>(myEnum1->Current);
Console::WriteLine( " {0,-5} : {1}", k, myCol->Item[ k ] );
}
Console::WriteLine();
}
/*
This code produces the following output.
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
*/
继承层次结构
System.Object
System.Collections.DictionaryBase
派生类
线程安全
此类型的公共静态（在 Visual Basic 中为 Shared）成员是线程安全的。但不能保证任何实例成员是线程安全的。
此实现不为 DictionaryBase 提供同步（线程安全）的包装，但派生类可以使用 SyncRoot 属性创建各自的 DictionaryBase 同步版本。
通过集合枚举在本质上不是一个线程安全的过程。即使一个集合已进行同步，其他线程仍可以修改该集合，这将导致枚举数引发异常。若要在枚举过程中保证线程安全，可以在整个枚举过程中锁定集合，或者捕捉由于其他线程进行的更改而引发的异常。
平台
Windows 98、Windows 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
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
请参见
参考
DictionaryBase 成员
System.Collections 命名空间
System.Collections.Hashtable
System.Collections.IDictionary
System.Collections.Generic