ArrayList::IsReadOnly Property
Gets a value indicating whether the ArrayList is read-only.
Assembly: mscorlib (in mscorlib.dll)
Property Value
Type: System::Booleantrue if the ArrayList is read-only; otherwise, false. The default is false.
Implements
IList::IsReadOnlyA collection that is read-only does not allow the addition, removal, or modification of elements after the collection is created.
A collection that is read-only is simply a collection with a wrapper that prevents modifying the collection; therefore, if changes are made to the underlying collection, the read-only collection reflects those changes.
Retrieving the value of this property is an O(1) operation.
The following code example shows how to create a read-only wrapper around an ArrayList and how to determine if an ArrayList is read-only.
#using <system.dll> using namespace System; using namespace System::Collections; int main() { // Creates and initializes a new ArrayList. ArrayList^ myAL = gcnew ArrayList; myAL->Add( "red" ); myAL->Add( "orange" ); myAL->Add( "yellow" ); // Creates a read-only copy of the ArrayList. ArrayList^ myReadOnlyAL = ArrayList::ReadOnly( myAL ); // Displays whether the ArrayList is read-only or writable. Console::WriteLine( "myAL is {0}.", myAL->IsReadOnly ? (String^)"read-only" : "writable" ); Console::WriteLine( "myReadOnlyAL is {0}.", myReadOnlyAL->IsReadOnly ? (String^)"read-only" : "writable" ); // Displays the contents of both collections. Console::WriteLine( "\nInitially," ); Console::WriteLine( "The original ArrayList myAL contains:" ); for ( int i(0); i < myAL->Count; ++i ) Console::WriteLine( " {0}", static_cast<String^>(myAL[ i ]) ); Console::WriteLine( "The read-only ArrayList myReadOnlyAL contains:" ); for ( int i(0); i < myReadOnlyAL->Count; ++i ) Console::WriteLine( " {0}", static_cast<String^>(myReadOnlyAL[ i ]) ); // Adding an element to a read-only ArrayList throws an exception. Console::WriteLine( "\nTrying to add a new element to the read-only ArrayList:" ); try { myReadOnlyAL->Add( "green" ); } catch ( Exception^ myException ) { Console::WriteLine( String::Concat( "Exception: ", myException->ToString() ) ); } // Adding an element to the original ArrayList affects the read-only ArrayList. myAL->Add( "blue" ); // Displays the contents of both collections again. Console::WriteLine( "\nAfter adding a new element to the original ArrayList," ); Console::WriteLine( "The original ArrayList myAL contains:" ); for ( int i(0); i < myAL->Count; ++i ) Console::WriteLine( " {0}", static_cast<String^>(myAL[ i ]) ); Console::WriteLine( "The read-only ArrayList myReadOnlyAL contains:" ); for ( int i(0); i < myReadOnlyAL->Count; ++i ) Console::WriteLine( " {0}", static_cast<String^>(myReadOnlyAL[ i ]) ); } /* This code produces the following output. myAL is writable. myReadOnlyAL is read-only. Initially, The original ArrayList myAL contains: red orange yellow The read-only ArrayList myReadOnlyAL contains: red orange yellow Trying to add a new element to the read-only ArrayList: Exception: System.NotSupportedException: Collection is read-only. at System.Collections.ReadOnlyArrayList.Add(Object obj) at SamplesArrayList.Main() After adding a new element to the original ArrayList, The original ArrayList myAL contains: red orange yellow blue The read-only ArrayList myReadOnlyAL contains: red orange yellow blue */
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.