HybridCollection.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.Activities / System / Activities / HybridCollection.cs / 1305376 / HybridCollection.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------

namespace System.Activities 
{
    using System; 
    using System.Runtime.Serialization; 
    using System.Collections.Generic;
    using System.Runtime; 
    using System.Collections.ObjectModel;

    // used internally for performance in cases where a common usage pattern is a single item
    [DataContract] 
    class HybridCollection
        where T : class 
    { 
        [DataMember(EmitDefaultValue = false)]
        List multipleItems; 
        [DataMember(EmitDefaultValue = false)]
        T singleItem;

        public HybridCollection() 
        {
        } 
 
        public HybridCollection(T initialItem)
        { 
            Fx.Assert(initialItem != null, "null is used as a sentinal value and is not a valid item value for a hybrid collection");
            this.singleItem = initialItem;
        }
 
        public T this[int index]
        { 
            get 
            {
                if (this.singleItem != null) 
                {
                    Fx.Assert(index == 0, "Out of range with a single item");
                    return this.singleItem;
                } 
                else if (this.multipleItems != null)
                { 
                    Fx.Assert(index >= 0 && index < this.multipleItems.Count, "Out of range with multiple items."); 

                    return this.multipleItems[index]; 
                }

                Fx.Assert("Out of range.  There were no items in the HybridCollection.");
                return default(T); 
            }
        } 
 
        public int Count
        { 
            get
            {
                if (this.singleItem != null)
                { 
                    return 1;
                } 
 
                if (this.multipleItems != null)
                { 
                    return this.multipleItems.Count;
                }

                return 0; 
            }
        } 
 
        protected T SingleItem
        { 
            get
            {
                return this.singleItem;
            } 
        }
 
        protected IList MultipleItems 
        {
            get 
            {
                return this.multipleItems;
            }
        } 

        public void Add(T item) 
        { 
            Fx.Assert(item != null, "null is used as a sentinal value and is not a valid item value for a hybrid collection");
            if (this.multipleItems != null) 
            {
                this.multipleItems.Add(item);
            }
            else if (this.singleItem != null) 
            {
                this.multipleItems = new List(2); 
                this.multipleItems.Add(this.singleItem); 
                this.multipleItems.Add(item);
                this.singleItem = null; 
            }
            else
            {
                this.singleItem = item; 
            }
        } 
 
        public ReadOnlyCollection AsReadOnly()
        { 
            if (this.multipleItems != null)
            {
                return new ReadOnlyCollection(this.multipleItems);
            } 
            else if (this.singleItem != null)
            { 
                return new ReadOnlyCollection(new T[1] { this.singleItem }); 
            }
            else 
            {
                return new ReadOnlyCollection(new T[0]);
            }
        } 

        // generally used for serialization purposes 
        public void Compress() 
        {
            if (this.multipleItems != null && this.multipleItems.Count == 1) 
            {
                this.singleItem = this.multipleItems[0];
                this.multipleItems = null;
            } 
        }
 
        public void Remove(T item) 
        {
            Remove(item, false); 
        }

        internal void Remove(T item, bool searchingFromEnd)
        { 
            if (this.singleItem != null)
            { 
                Fx.Assert(object.Equals(item, this.singleItem), "The given item should be in this list. Something is wrong in our housekeeping."); 
                this.singleItem = null;
            } 
            else
            {
                Fx.Assert(this.multipleItems != null && this.multipleItems.Contains(item), "The given item should be in this list. Something is wrong in our housekeeping.");
                int position = (searchingFromEnd) ? this.multipleItems.LastIndexOf(item) : this.multipleItems.IndexOf(item); 
                if (position != -1)
                { 
                    this.multipleItems.RemoveAt(position); 
                }
            } 
        }
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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HybridCollection.cs source code in C# .NET

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