NameObjectCollectionBase.BaseClear Method

Definition

Namespace:

System.Collections.Specialized

Assembly:

System.Collections.Specialized.dll

Source:

NameObjectCollectionBase.cs

Removes all entries from the NameObjectCollectionBase instance.

protected:
 void BaseClear();

protected void BaseClear ();

member this.BaseClear : unit -> unit

Protected Sub BaseClear ()

Exceptions

NotSupportedException

The collection is read-only.

Examples

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

#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):

*/

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):

*/

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

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

End Class


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

   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

End Class


'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):

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.