DictionaryBase Class
Provides the abstract (MustInherit in Visual Basic) base class for a strongly typed collection of key-and-value pairs.
For a list of all members of this type, see DictionaryBase Members.
System.Object
System.Collections.DictionaryBase
Derived classes
[Visual Basic] <Serializable> MustInherit Public Class DictionaryBase Implements IDictionary, ICollection, IEnumerable [C#] [Serializable] public abstract class DictionaryBase : IDictionary, ICollection, IEnumerable [C++] [Serializable] public __gc __abstract class DictionaryBase : public IDictionary, ICollection, IEnumerable [JScript] public Serializable abstract class DictionaryBase implements IDictionary, ICollection, IEnumerable
Thread Safety
Public static (Shared in Visual Basic) members of this type are safe for multithreaded operations. 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 could 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.
Remarks
[Visual Basic, C#] 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-and-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:
[C#] foreach (DictionaryEntry myDE in myDictionary) {...} [Visual Basic] Dim myDE As DictionaryEntry For Each myDE In myDictionary ... Next myDE
[Visual Basic, C#] The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.
Notes to Implementers:
This base class is provided to make it easier for implementers to create a strongly typed custom collection. Implementers should extend this base class instead of creating their own.
Members of this base class are protected and are intended to be used through a derived class only.
Example
[Visual Basic, C#, C++] 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.
[Visual Basic] 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 key.GetType() Is Type.GetType("System.String") 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 value.GetType() Is Type.GetType("System.String") 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 key.GetType() Is Type.GetType("System.String") 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 key.GetType() Is Type.GetType("System.String") 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 newValue.GetType() Is Type.GetType("System.String") 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 key.GetType() Is Type.GetType("System.String") 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 value.GetType() Is Type.GetType("System.String") 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") ' 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() ' Displays the contents of the collection using the enumerator. Console.WriteLine("Initial contents of the collection:") PrintKeysAndValues(mySSC) ' 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 using the Keys property. Console.WriteLine("New state of the collection:") PrintKeysAndValues3(mySSC) End Sub 'Main ' Uses the enumerator. Public Shared Sub PrintKeysAndValues(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 'PrintKeysAndValues ' Uses the foreach statement which hides the complexity of the enumerator. Public Shared Sub PrintKeysAndValues2(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 '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. ' '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() ' 'Initial contents of the collection: ' One : a ' Four : abcd ' Three : abc ' Two : ab ' Five : abcde ' 'Contains "Three": True 'Contains "Twelve": False ' 'New state of the collection: ' One : a ' Four : abcd ' Three : abc ' Five : abcde [C#] 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() != 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() != 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" ); } } protected override void OnRemove( Object key, Object value ) { if ( key.GetType() != 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" ); } } protected override void OnSet( Object key, Object oldValue, Object newValue ) { if ( key.GetType() != 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() != 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" ); } } protected override void OnValidate( Object key, Object value ) { if ( key.GetType() != 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() != 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" ); } } } 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" ); // 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(); // Displays the contents of the collection using the enumerator. Console.WriteLine( "Initial contents of the collection:" ); PrintKeysAndValues( mySSC ); // 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 using the Keys property. Console.WriteLine( "New state of the collection:" ); PrintKeysAndValues3( mySSC ); } // Uses the enumerator. public static void PrintKeysAndValues( 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 foreach statement which hides the complexity of the enumerator. public static void PrintKeysAndValues2( ShortStringDictionary myCol ) { foreach ( DictionaryEntry myDE in myCol ) 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. 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() Initial contents of the collection: One : a Four : abcd Three : abc Two : ab Five : abcde Contains "Three": True Contains "Twelve": False New state of the collection: One : a Four : abcd Three : abc Five : abcde */ [C++] #using <mscorlib.dll> using namespace System; using namespace System::Collections; public __gc class ShortStringDictionary : public DictionaryBase { public: __property String* get_Item( String* key ) { return __try_cast<String*>(Dictionary->Item[key]); } __property void set_Item( String* key, String* value ) { Dictionary->Item[key] = value; } __property ICollection* get_Keys() { return(Dictionary->Keys); } __property ICollection* get_Values() { 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: void OnInsert(Object* key, Object* value) { if (key->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"key must be of type String.", S"key"); else { String* strKey = __try_cast<String*>(key); if (strKey->Length > 5) throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key"); } if (value->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"value must be of type String.", S"value"); else { String* strValue = __try_cast<String*>(value); if (strValue->Length > 5) throw new ArgumentException(S"value must be no more than 5 characters in length.", S"value"); } } void OnRemove(Object* key, Object* value) { if (key->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"key must be of type String.", S"key"); else { String* strKey = __try_cast<String*>(key); if (strKey->Length > 5) throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key"); } } void OnSet(Object* key, Object* oldValue, Object* newValue) { if (key->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"key must be of type String.", S"key"); else { String* strKey = __try_cast<String*>(key); if (strKey->Length > 5) throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key"); } if (newValue->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"newValue must be of type String.", S"newValue"); else { String* strValue = __try_cast<String*>(newValue); if (strValue->Length > 5) throw new ArgumentException(S"newValue must be no more than 5 characters in length.", S"newValue"); } } void OnValidate(Object* key, Object* value) { if (key->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"key must be of type String.", S"key"); else { String* strKey = __try_cast<String*>(key); if (strKey->Length > 5) throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key"); } if (value->GetType() != Type::GetType(S"System.String")) throw new ArgumentException(S"value must be of type String.", S"value"); else { String* strValue = __try_cast<String*>(value); if (strValue->Length > 5) throw new ArgumentException(S"value must be no more than 5 characters in length.", S"value"); } } }; // Uses the enumerator. void PrintKeysAndValues(ShortStringDictionary* myCol) { DictionaryEntry* myDE; System::Collections::IEnumerator* myEnumerator = myCol->GetEnumerator(); while (myEnumerator->MoveNext()) if (myEnumerator->Current != 0) { myDE = __try_cast<DictionaryEntry*>(myEnumerator->Current); Console::WriteLine(S" {0, -5} : {1}", myDE->Key, myDE->Value); } Console::WriteLine(); } // Uses the foreach statement which hides the complexity of the enumerator. void PrintKeysAndValues2(ShortStringDictionary* myCol) { IEnumerator* myEnum = myCol->GetEnumerator(); while (myEnum->MoveNext()) { DictionaryEntry* myDE = __try_cast<DictionaryEntry*>(myEnum->Current); Console::WriteLine(S" {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* myEnum = myKeys->GetEnumerator(); while (myEnum->MoveNext()) { String* k = __try_cast<String*>(myEnum->Current); Console::WriteLine(S" {0, -5} : {1}", k, myCol->Item[k]); Console::WriteLine(); } } int main() { // Creates and initializes a new DictionaryBase. ShortStringDictionary* mySSC = new ShortStringDictionary(); // Adds elements to the collection. mySSC->Add(S"One", S"a"); mySSC->Add(S"Two", S"ab"); mySSC->Add(S"Three", S"abc"); mySSC->Add(S"Four", S"abcd"); mySSC->Add(S"Five", S"abcde"); // Tries to add a value that is too long. try { mySSC->Add(S"Ten", S"abcdefghij"); } catch (ArgumentException* e) { Console::WriteLine(e); } // Tries to add a key that is too long. try { mySSC->Add(S"Eleven", S"ijk"); } catch (ArgumentException* e) { Console::WriteLine(e); } Console::WriteLine(); // Displays the contents of the collection using the enumerator. Console::WriteLine(S"Initial contents of the collection:"); PrintKeysAndValues(mySSC); // Searches the collection with Contains. Console::WriteLine(S"Contains \"Three\": {0}", __box(mySSC->Contains(S"Three"))); Console::WriteLine(S"Contains \"Twelve\": {0}", __box(mySSC->Contains(S"Twelve"))); Console::WriteLine(); // Removes an element from the collection. mySSC->Remove(S"Two"); // Displays the contents of the collection using the Keys property. Console::WriteLine(S"New state of the collection:"); PrintKeysAndValues3(mySSC); } /* This code produces the following output. 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() Initial contents of the collection: One : a Four : abcd Three : abc Two : ab Five : abcde Contains S"Three": True Contains S"Twelve": False New state of the collection: One : a Four : abcd Three : abc Five : abcde */
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Requirements
Namespace: System.Collections
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
Assembly: Mscorlib (in Mscorlib.dll)
See Also
DictionaryBase Members | System.Collections Namespace | System.Collections.Hashtable | System.Collections.IDictionary | Performing Culture-Insensitive String Operations