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NameObjectCollectionBase.BaseHasKeys Method

Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not a null reference (Nothing in Visual Basic).

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

protected:
bool BaseHasKeys ()
protected boolean BaseHasKeys ()
protected function BaseHasKeys () : boolean
Not applicable.

Return Value

true if the NameObjectCollectionBase instance contains entries whose keys are not a null reference (Nothing in Visual Basic); otherwise, false.

This method is an O(1) operation.

The following code example uses BaseHasKeys to determine if the collection contains keys that are not a null reference (Nothing in Visual Basic).

#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;

public ref class MyCollection : public NameObjectCollectionBase  {

private:
   DictionaryEntry^ _de;

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

   // Creates an empty collection.
   MyCollection()  {
      _de = gcnew DictionaryEntry();
   }

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

   // Gets a value indicating whether the collection contains keys that are not a null reference.
   property Boolean HasKeys  {
      Boolean get()  {
         return( this->BaseHasKeys() );
      }
   }
};

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

int main()  {

   // Creates an empty MyCollection instance.
   MyCollection^ myCol = gcnew MyCollection();
   Console::WriteLine( "Initial state of the collection (Count = {0}):", myCol->Count );
   PrintKeysAndValues( myCol );
   Console::WriteLine( "HasKeys? {0}", myCol->HasKeys );

   Console::WriteLine();

   // Adds an item to the collection.
   myCol->Add( "blue", "sky" );
   Console::WriteLine( "Initial state of the collection (Count = {0}):", myCol->Count );
   PrintKeysAndValues( myCol );
   Console::WriteLine( "HasKeys? {0}", myCol->HasKeys );

}

/*
This code produces the following output.

Initial state of the collection (Count = 0):
HasKeys? False

Initial state of the collection (Count = 1):
[0] : blue, sky
HasKeys? True

*/

import System.* ;
import System.Collections.* ;
import System.Collections.Specialized.* ;

public class MyCollection extends NameObjectCollectionBase
{
    private DictionaryEntry _de =  new DictionaryEntry();

    // Gets a key-and-value pair (DictionaryEntry) using an index.
    /** @property 
     */
    public DictionaryEntry get_Item(int index)
    {
        _de.set_Key(this.BaseGetKey(index));
        _de.set_Value(this.BaseGet(index));
        return _de ;
    } //get_Item

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

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

    // Gets a value indicating whether the collection contains keys that are
    // not a null reference.
    /** @property 
     */
    public boolean get_HasKeys()
    {
        return this.BaseHasKeys() ;
    } //get_HasKeys
} //MyCollection


public class SamplesNameObjectCollectionBase
{
    public static void main(String[] args)
    {            
        // Creates an empty MyCollection instance.
        MyCollection myCol =  new MyCollection();
        Console.WriteLine("Initial state of the collection (Count = {0}):",
            System.Convert.ToString( myCol.get_Count()));
        PrintKeysAndValues(myCol);
        Console.WriteLine("HasKeys? {0}", 
            System.Convert.ToString(myCol.get_HasKeys()));
        Console.WriteLine();
        
        // Adds an item to the collection.
        myCol.Add("blue", "sky");
        Console.WriteLine("Initial state of the collection (Count = {0}):",
            System.Convert.ToString(myCol.get_Count()));
        PrintKeysAndValues(myCol);
        Console.WriteLine("HasKeys? {0}",
            System.Convert.ToString(myCol.get_HasKeys()));
    } //main

    public static void PrintKeysAndValues(MyCollection myCol) 
    {
        for (int i=0; i < myCol.get_Count(); i++) {        
            Console.WriteLine("[{0}] : {1}, {2}",System.Convert.ToString(i), 
                myCol.get_Item(i).get_Key(), myCol.get_Item(i).get_Value());
        } 
    } //PrintKeysAndValues
} //SamplesNameObjectCollectionBase
 
/*
This code produces the following output.

Initial state of the collection (Count = 0):
HasKeys? False

Initial state of the collection (Count = 1):
[0] : blue, sky
HasKeys? True

*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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