NameObjectCollectionBase.BaseClear Method (System.Collections.Specialized)

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.NET Framework Class Library
NameObjectCollectionBase.BaseClear Method

Removes all entries from the NameObjectCollectionBase instance.

Namespace:  System.Collections.Specialized
Assembly:  System (in System.dll)
Syntax

Visual Basic
Protected Sub BaseClear
C#
protected void BaseClear()
Visual C++
protected:
void BaseClear()
F#
member BaseClear : unit -> unit 

Exceptions

Exception Condition
NotSupportedException

The collection is read-only.

Remarks

Count is set to zero, and references to other objects from elements of the collection are also released.

This method is an O(1) operation.

Examples

The following code example uses BaseClear to remove all elements from a NameObjectCollectionBase.

Visual Basic

Imports System
Imports System.Collections
Imports System.Collections.Specialized

Public Class MyCollection
   Inherits NameObjectCollectionBase

   Private _de As New DictionaryEntry()

   ' Gets a key-and-value pair (DictionaryEntry) using an index.
   Default Public ReadOnly Property Item(index As Integer) As DictionaryEntry
      Get
         _de.Key = Me.BaseGetKey(index)
         _de.Value = Me.BaseGet(index)
         Return _de
      End Get
   End Property

   ' Adds elements from an IDictionary into the new collection.
   Public Sub New(d As IDictionary)
      Dim de As DictionaryEntry
      For Each de In  d
         Me.BaseAdd(CType(de.Key, [String]), de.Value)
      Next de
   End Sub 'New

   ' Clears all the elements in the collection.
   Public Sub Clear()
      Me.BaseClear()
   End Sub 'Clear

End Class 'MyCollection


Public Class SamplesNameObjectCollectionBase   

   Public Shared Sub Main()

      ' Creates and initializes a new MyCollection instance.
      Dim d = New ListDictionary()
      d.Add("red", "apple")
      d.Add("yellow", "banana")
      d.Add("green", "pear")
      Dim myCol As New MyCollection(d)
      Console.WriteLine("Initial state of the collection (Count = {0}):", myCol.Count)
      PrintKeysAndValues(myCol)

      ' Removes all elements from the collection.
      myCol.Clear()
      Console.WriteLine("After clearing the collection (Count = {0}):", myCol.Count)
      PrintKeysAndValues(myCol)

   End Sub 'Main

   Public Shared Sub PrintKeysAndValues(myCol As MyCollection)
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("[{0}] : {1}, {2}", i, myCol(i).Key, myCol(i).Value)
      Next i
   End Sub 'PrintKeysAndValues

End Class 'SamplesNameObjectCollectionBase 


'This code produces the following output.
'
'Initial state of the collection (Count = 3):
'[0] : red, apple
'[1] : yellow, banana
'[2] : green, pear
'After clearing the collection (Count = 0):



C#

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

public class MyCollection : NameObjectCollectionBase  {

   private DictionaryEntry _de = new DictionaryEntry();

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

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

   // 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 instance.
      IDictionary d = new ListDictionary();
      d.Add( "red", "apple" );
      d.Add( "yellow", "banana" );
      d.Add( "green", "pear" );
      MyCollection myCol = new MyCollection( d );
      Console.WriteLine( "Initial state of the collection (Count = {0}):", myCol.Count );
      PrintKeysAndValues( myCol );

      // Removes all elements from the collection.
      myCol.Clear();
      Console.WriteLine( "After clearing the collection (Count = {0}):", myCol.Count );
      PrintKeysAndValues( myCol );

   }

   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 );
      }
   }

}


/*
This code produces the following output.

Initial state of the collection (Count = 3):
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
After clearing the collection (Count = 0):

*/


Visual C++

#using <system.dll>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
public ref class MyCollection: public NameObjectCollectionBase
{
private:
   DictionaryEntry _de;

public:

   property DictionaryEntry Item [ int ]
   {
      // Gets a key-and-value pair (DictionaryEntry) using an index.
      DictionaryEntry get( int index )
      {
         _de.Key = this->BaseGetKey( index );
         _de.Value = this->BaseGet( index );
         return (_de);
      }
   }

   // Adds elements from an IDictionary* into the new collection.
   MyCollection( IDictionary^ d )
   {
      IEnumerator^ myEnum = d->GetEnumerator();
      while ( myEnum->MoveNext() )
      {
         DictionaryEntry^ de = safe_cast<DictionaryEntry^>(myEnum->Current);
         this->BaseAdd( safe_cast<String^>(de->Key), de->Value );
      }
   }

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

static void PrintKeysAndValues( MyCollection^ myCol )
{
   for ( int i = 0; i < myCol->Count; i++ )
   {
      Console::WriteLine( "[{0}] : {1}, {2}", i, myCol->Item[ i ].Key, myCol->Item[ i ].Value );

   }
}

int main()
{
   // Creates and initializes a new MyCollection instance.
   IDictionary^ d = gcnew ListDictionary;
   d->Add( "red", "apple" );
   d->Add( "yellow", "banana" );
   d->Add( "green", "pear" );
   MyCollection^ myCol = gcnew MyCollection( d );
   Console::WriteLine( "Initial state of the collection (Count = {0}):", myCol->Count );
   PrintKeysAndValues( myCol );

   // Removes all elements from the collection.
   myCol->Clear();
   Console::WriteLine( "After clearing the collection (Count = {0}):", myCol->Count );
   PrintKeysAndValues( myCol );
}

/*
This code produces the following output.

Initial state of the collection (Count = 3):
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
After clearing the collection (Count = 0):

*/


Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Platforms

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.
See Also

Reference