WeakReadOnlyCollection.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Base / System / Collections / ObjectModel / WeakReadOnlyCollection.cs / 1305600 / WeakReadOnlyCollection.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 

// This is basically copied from ReadOnlyCollection, with just enough modification 
// to support storage of items as WeakReferences.  Use of internal BCL features 
// is commented out.
 
// Most of the O(N) operations - Contains, IndexOf, etc. -
// are implemented by simply exploding the base list into a List.  This isn't
// particularly efficient, but we don't expect to use these methods very often.
 
// The important scenario is one where we need WR not because we expect the targets
// to die (we don't), but because we need to avoid creating cycles containing the 
// WeakReadOnlyCollection.  Thus we don't check for WR.Target==null. 

namespace System.Collections.ObjectModel 
{
    using System;
    using System.Collections;
    using System.Collections.Generic; 
    using System.Diagnostics;
    using System.Windows; 
    using MS.Internal.WindowsBase;      // [FriendAccessAllowed] 

    [Serializable] 
    [System.Runtime.InteropServices.ComVisible(false)]
    //[DebuggerTypeProxy(typeof(Mscorlib_CollectionDebugView<>))]
    [DebuggerDisplay("Count = {Count}")]
    [FriendAccessAllowed] 
    internal class WeakReadOnlyCollection: IList, IList
    { 
        //IList list; 
        IList list;
        [NonSerialized] 
        private Object _syncRoot;

        public WeakReadOnlyCollection(IList list) {  // assumption: the WRs in list refer to T's
            if (list == null) { 
                throw new ArgumentNullException("list");
            } 
            this.list = list; 
        }
 
        public int Count {
            get { return list.Count; }
        }
 
        public T this[int index] {
            //get { return list[index]; } 
            get { return (T)list[index].Target; } 
        }
 
        public bool Contains(T value) {
            //return list.Contains(value);
            return CreateDereferencedList().Contains(value);
        } 

        public void CopyTo(T[] array, int index) { 
            //list.CopyTo(array, index); 
            CreateDereferencedList().CopyTo(array, index);
        } 

        public IEnumerator GetEnumerator() {
            //return list.GetEnumerator();
            return new WeakEnumerator(list.GetEnumerator()); 
        }
 
        public int IndexOf(T value) { 
            //return list.IndexOf(value);
            return CreateDereferencedList().IndexOf(value); 
        }

        /*
        protected IList Items { 
            get {
                return list; 
            } 
        }
        */ 

        bool ICollection.IsReadOnly {
            get { return true; }
        } 

        T IList.this[int index] { 
            //get { return list[index]; } 
            get { return (T)list[index].Target; }
            set { 
                //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
                throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
            }
        } 

        void ICollection.Add(T value) { 
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection); 
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
        } 

        void ICollection.Clear() {
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection)); 
        }
 
        void IList.Insert(int index, T value) { 
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection)); 
        }

        bool ICollection.Remove(T value) {
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection); 
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
            //return false; 
        } 

        void IList.RemoveAt(int index) { 
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
        }
 
        IEnumerator IEnumerable.GetEnumerator() {
            //return ((IEnumerable)list).GetEnumerator(); 
            return new WeakEnumerator(((IEnumerable)list).GetEnumerator()); 
        }
 
        bool ICollection.IsSynchronized {
            get { return false; }
        }
 
        object ICollection.SyncRoot {
            get { 
                if( _syncRoot == null) { 
                    ICollection c = list as ICollection;
                    if( c != null) { 
                        _syncRoot = c.SyncRoot;
                    }
                    else {
                        System.Threading.Interlocked.CompareExchange(ref _syncRoot, new Object(), null); 
                    }
                } 
                return _syncRoot; 
            }
        } 

        void ICollection.CopyTo(Array array, int index) {
            if (array==null) {
                //ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array); 
                throw new ArgumentNullException("array");
            } 
 
            if (array.Rank != 1) {
                //ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported); 
                throw new ArgumentException(SR.Get(SRID.Arg_RankMultiDimNotSupported));
            }

            if( array.GetLowerBound(0) != 0 ) { 
                //ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
                throw new ArgumentException(SR.Get(SRID.Arg_NonZeroLowerBound)); 
            } 

            if (index < 0) { 
                //ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.arrayIndex, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
                throw new ArgumentOutOfRangeException("index", SR.Get(SRID.ArgumentOutOfRange_NeedNonNegNum));
            }
 
            if (array.Length - index < Count) {
                //ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall); 
                throw new ArgumentException(SR.Get(SRID.Arg_ArrayPlusOffTooSmall)); 
            }
 
            IList dlist = CreateDereferencedList();
            T[] items = array as T[];
            if (items != null) {
                dlist.CopyTo(items, index); 
            }
            else { 
                // 
                // Catch the obvious case assignment will fail.
                // We can found all possible problems by doing the check though. 
                // For example, if the element type of the Array is derived from T,
                // we can't figure out if we can successfully copy the element beforehand.
                //
                Type targetType = array.GetType().GetElementType(); 
                Type sourceType = typeof(T);
                if(!(targetType.IsAssignableFrom(sourceType) || sourceType.IsAssignableFrom(targetType))) { 
                    //ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType); 
                    throw new ArgumentException(SR.Get(SRID.Argument_InvalidArrayType));
                } 

                //
                // We can't cast array of value type to object[], so we don't support
                // widening of primitive types here. 
                //
                object[] objects = array as object[]; 
                if( objects == null) { 
                    //ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType);
                    throw new ArgumentException(SR.Get(SRID.Argument_InvalidArrayType)); 
                }

                int count = dlist.Count;
                try { 
                    for (int i = 0; i < count; i++) {
                        objects[index++] = dlist[i]; 
                    } 
                }
                catch(ArrayTypeMismatchException) { 
                    //ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType);
                    throw new ArgumentException(SR.Get(SRID.Argument_InvalidArrayType));
                }
            } 
        }
 
        bool IList.IsFixedSize { 
            get { return true; }
        } 

        bool IList.IsReadOnly {
            get { return true; }
        } 

        object IList.this[int index] { 
            //get { return list[index]; } 
            get { return (T)list[index].Target; }
            set { 
                //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
                throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
            }
        } 

        int IList.Add(object value) { 
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection); 
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
            //return -1; 
        }

        void IList.Clear() {
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection); 
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
        } 
 
        private static bool IsCompatibleObject(object value) {
            // Non-null values are fine.  Only accept nulls if T is a class or Nullable. 
            // Note that default(T) is not equal to null for value types except when T is Nullable.
            return ((value is T) || (value == null && default(T) == null));
        }
 
        bool IList.Contains(object value) {
            if(IsCompatibleObject(value)) { 
                return Contains((T) value); 
            }
            return false; 
        }

        int IList.IndexOf(object value) {
            if(IsCompatibleObject(value)) { 
                return IndexOf((T)value);
            } 
            return -1; 
        }
 
        void IList.Insert(int index, object value) {
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
        } 

        void IList.Remove(object value) { 
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection); 
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection));
        } 

        void IList.RemoveAt(int index) {
            //ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
            throw new NotSupportedException(SR.Get(SRID.NotSupported_ReadOnlyCollection)); 
        }
 
        IList CreateDereferencedList() 
        {
            int n = list.Count; 
            List newList = new List(n);
            for (int i=0; i, IEnumerator 
        {
            public WeakEnumerator(IEnumerator ie) {
                this.ie = ie;
            } 

            public void Dispose() { 
            } 

            public bool MoveNext() { 
                return ie.MoveNext();
            }

            public T Current { 
                get {
                    WeakReference wr = ie.Current as WeakReference; 
                    if (wr != null) 
                        return (T)wr.Target;
                    else 
                        return default(T);
                }
            }
 
            object IEnumerator.Current {
                get { return Current; } 
            } 

            void IEnumerator.Reset() { 
                ie.Reset();
            }

            private IEnumerator ie; 
        }
    } 
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

                        

                        
                        
                    
                    

                        
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