using System;using System.Runtime;using System.Runtime.CompilerServices;namespace System.Collections.Specialized{    /// <summary>Describes the action that caused a <see cref="E:System.Collections.Specialized.INotifyCollectionChanged.CollectionChanged" /> event. </summary>    [__DynamicallyInvokable]    public enum NotifyCollectionChangedAction    {        /// <summary>One or more items were added to the collection.</summary>        Add,        /// <summary>One or more items were removed from the collection.</summary>        Remove,        /// <summary>One or more items were replaced in the collection.</summary>        Replace,        /// <summary>One or more items were moved within the collection.</summary>        Move,        /// <summary>The content of the collection changed dramatically.</summary>        Reset    }        /// <summary>Provides data for the <see cref="E:System.Collections.Specialized.INotifyCollectionChanged.CollectionChanged" /> event.</summary>    [__DynamicallyInvokable]    public class NotifyCollectionChangedEventArgs : EventArgs    {        private NotifyCollectionChangedAction _action;        private IList _newItems;        private IList _oldItems;        private int _newStartingIndex = -1;        private int _oldStartingIndex = -1;        /// <summary>Gets the action that caused the event. </summary>        /// <returns>A <see cref="T:System.Collections.Specialized.NotifyCollectionChangedAction" /> value that describes the action that caused the event.</returns>        [__DynamicallyInvokable]        public NotifyCollectionChangedAction Action        {            [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]            get            {                return this._action;            }        }        /// <summary>Gets the list of new items involved in the change.</summary>        /// <returns>The list of new items involved in the change.</returns>        [__DynamicallyInvokable]        public IList NewItems        {            [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]            get            {                return this._newItems;            }        }        /// <summary>Gets the list of items affected by a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />, Remove, or Move action.</summary>        /// <returns>The list of items affected by a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />, Remove, or Move action.</returns>        [__DynamicallyInvokable]        public IList OldItems        {            [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]            get            {                return this._oldItems;            }        }        /// <summary>Gets the index at which the change occurred.</summary>        /// <returns>The zero-based index at which the change occurred.</returns>        [__DynamicallyInvokable]        public int NewStartingIndex        {            [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]            get            {                return this._newStartingIndex;            }        }        /// <summary>Gets the index at which a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" />, Remove, or Replace action occurred.</summary>        /// <returns>The zero-based index at which a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" />, Remove, or Replace action occurred.</returns>        [__DynamicallyInvokable]        public int OldStartingIndex        {            [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]            get            {                return this._oldStartingIndex;            }        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" /> change.</summary>        /// <param name="action">The action that caused the event. This must be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" />.</param>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action)        {            if (action != NotifyCollectionChangedAction.Reset)            {                throw new ArgumentException("WrongActionForCtor");            }            this.InitializeAdd(action, null, -1);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a one-item change.</summary>        /// <param name="action">The action that caused the event. This can be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" />, <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Add" />, or <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Remove" />.</param>        /// <param name="changedItem">The item that is affected by the change.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Reset, Add, or Remove, or if <paramref name="action" /> is Reset and <paramref name="changedItem" /> is not null.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object changedItem)        {            if (action != NotifyCollectionChangedAction.Add && action != NotifyCollectionChangedAction.Remove && action != NotifyCollectionChangedAction.Reset)            {                throw new ArgumentException("MustBeResetAddOrRemoveActionForCtor");            }            if (action != NotifyCollectionChangedAction.Reset)            {                this.InitializeAddOrRemove(action, new object[]				{					changedItem				}, -1);                return;            }            if (changedItem != null)            {                throw new ArgumentException("ResetActionRequiresNullItem");            }            this.InitializeAdd(action, null, -1);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a one-item change.</summary>        /// <param name="action">The action that caused the event. This can be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" />, <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Add" />, or <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Remove" />.</param>        /// <param name="changedItem">The item that is affected by the change.</param>        /// <param name="index">The index where the change occurred.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Reset, Add, or Remove, or if <paramref name="action" /> is Reset and either <paramref name="changedItems" /> is not null or <paramref name="index" /> is not -1.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object changedItem, int index)        {            if (action != NotifyCollectionChangedAction.Add && action != NotifyCollectionChangedAction.Remove && action != NotifyCollectionChangedAction.Reset)            {                throw new ArgumentException("MustBeResetAddOrRemoveActionForCtor");            }            if (action != NotifyCollectionChangedAction.Reset)            {                this.InitializeAddOrRemove(action, new object[]				{					changedItem				}, index);                return;            }            if (changedItem != null)            {                throw new ArgumentException("ResetActionRequiresNullItem");            }            if (index != -1)            {                throw new ArgumentException("ResetActionRequiresIndexMinus1");            }            this.InitializeAdd(action, null, -1);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a multi-item change.</summary>        /// <param name="action">The action that caused the event. This can be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" />, <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Add" />, or <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Remove" />.</param>        /// <param name="changedItems">The items that are affected by the change.</param>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList changedItems)        {            if (action != NotifyCollectionChangedAction.Add && action != NotifyCollectionChangedAction.Remove && action != NotifyCollectionChangedAction.Reset)            {                throw new ArgumentException("MustBeResetAddOrRemoveActionForCtor");            }            if (action == NotifyCollectionChangedAction.Reset)            {                if (changedItems != null)                {                    throw new ArgumentException("ResetActionRequiresNullItem");                }                this.InitializeAdd(action, null, -1);                return;            }            else            {                if (changedItems == null)                {                    throw new ArgumentNullException("changedItems");                }                this.InitializeAddOrRemove(action, changedItems, -1);                return;            }        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a multi-item change or a <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" /> change.</summary>        /// <param name="action">The action that caused the event. This can be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Reset" />, <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Add" />, or <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Remove" />.</param>        /// <param name="changedItems">The items affected by the change.</param>        /// <param name="startingIndex">The index where the change occurred.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Reset, Add, or Remove, if <paramref name="action" /> is Reset and either <paramref name="changedItems" /> is not null or <paramref name="startingIndex" /> is not -1, or if action is Add or Remove and <paramref name="startingIndex" /> is less than -1.</exception>        /// <exception cref="T:System.ArgumentNullException">If <paramref name="action" /> is Add or Remove and <paramref name="changedItems" /> is null.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList changedItems, int startingIndex)        {            if (action != NotifyCollectionChangedAction.Add && action != NotifyCollectionChangedAction.Remove && action != NotifyCollectionChangedAction.Reset)            {                throw new ArgumentException("MustBeResetAddOrRemoveActionForCtor");            }            if (action == NotifyCollectionChangedAction.Reset)            {                if (changedItems != null)                {                    throw new ArgumentException("ResetActionRequiresNullItem");                }                if (startingIndex != -1)                {                    throw new ArgumentException("ResetActionRequiresIndexMinus1");                }                this.InitializeAdd(action, null, -1);                return;            }            else            {                if (changedItems == null)                {                    throw new ArgumentNullException("changedItems");                }                if (startingIndex < -1)                {                    throw new ArgumentException("IndexCannotBeNegative");                }                this.InitializeAddOrRemove(action, changedItems, startingIndex);                return;            }        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a one-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" /> change.</summary>        /// <param name="action">The action that caused the event. This can only be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />.</param>        /// <param name="newItem">The new item that is replacing the original item.</param>        /// <param name="oldItem">The original item that is replaced.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Replace.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object newItem, object oldItem)        {            if (action != NotifyCollectionChangedAction.Replace)            {                throw new ArgumentException("WrongActionForCtor");            }            this.InitializeMoveOrReplace(action, new object[]			{				newItem			}, new object[]			{				oldItem			}, -1, -1);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a one-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" /> change.</summary>        /// <param name="action">The action that caused the event. This can be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />.</param>        /// <param name="newItem">The new item that is replacing the original item.</param>        /// <param name="oldItem">The original item that is replaced.</param>        /// <param name="index">The index of the item being replaced.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Replace.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object newItem, object oldItem, int index)        {            if (action != NotifyCollectionChangedAction.Replace)            {                throw new ArgumentException("WrongActionForCtor");            }            this.InitializeMoveOrReplace(action, new object[]			{				newItem			}, new object[]			{				oldItem			}, index, index);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a multi-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" /> change.</summary>        /// <param name="action">The action that caused the event. This can only be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />.</param>        /// <param name="newItems">The new items that are replacing the original items.</param>        /// <param name="oldItems">The original items that are replaced.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Replace.</exception>        /// <exception cref="T:System.ArgumentNullException">If <paramref name="oldItems" /> or <paramref name="newItems" /> is null.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList newItems, IList oldItems)        {            if (action != NotifyCollectionChangedAction.Replace)            {                throw new ArgumentException("WrongActionForCtor");            }            if (newItems == null)            {                throw new ArgumentNullException("newItems");            }            if (oldItems == null)            {                throw new ArgumentNullException("oldItems");            }            this.InitializeMoveOrReplace(action, newItems, oldItems, -1, -1);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a multi-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" /> change.</summary>        /// <param name="action">The action that caused the event. This can only be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Replace" />.</param>        /// <param name="newItems">The new items that are replacing the original items.</param>        /// <param name="oldItems">The original items that are replaced.</param>        /// <param name="startingIndex">The index of the first item of the items that are being replaced.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Replace.</exception>        /// <exception cref="T:System.ArgumentNullException">If <paramref name="oldItems" /> or <paramref name="newItems" /> is null.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList newItems, IList oldItems, int startingIndex)        {            if (action != NotifyCollectionChangedAction.Replace)            {                throw new ArgumentException("WrongActionForCtor");            }            if (newItems == null)            {                throw new ArgumentNullException("newItems");            }            if (oldItems == null)            {                throw new ArgumentNullException("oldItems");            }            this.InitializeMoveOrReplace(action, newItems, oldItems, startingIndex, startingIndex);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a one-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" /> change.</summary>        /// <param name="action">The action that caused the event. This can only be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" />.</param>        /// <param name="changedItem">The item affected by the change.</param>        /// <param name="index">The new index for the changed item.</param>        /// <param name="oldIndex">The old index for the changed item.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Move or <paramref name="index" /> is less than 0.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object changedItem, int index, int oldIndex)        {            if (action != NotifyCollectionChangedAction.Move)            {                throw new ArgumentException("WrongActionForCtor");            }            if (index < 0)            {                throw new ArgumentException("IndexCannotBeNegative");            }            object[] array = new object[]			{				changedItem			};            this.InitializeMoveOrReplace(action, array, array, index, oldIndex);        }        /// <summary>Initializes a new instance of the <see cref="T:System.Collections.Specialized.NotifyCollectionChangedEventArgs" /> class that describes a multi-item <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" /> change.</summary>        /// <param name="action">The action that caused the event. This can only be set to <see cref="F:System.Collections.Specialized.NotifyCollectionChangedAction.Move" />.</param>        /// <param name="changedItems">The items affected by the change.</param>        /// <param name="index">The new index for the changed items.</param>        /// <param name="oldIndex">The old index for the changed items.</param>        /// <exception cref="T:System.ArgumentException">If <paramref name="action" /> is not Move or <paramref name="index" /> is less than 0.</exception>        [__DynamicallyInvokable]        public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList changedItems, int index, int oldIndex)        {            if (action != NotifyCollectionChangedAction.Move)            {                throw new ArgumentException("WrongActionForCtor");            }            if (index < 0)            {                throw new ArgumentException("IndexCannotBeNegative");            }            this.InitializeMoveOrReplace(action, changedItems, changedItems, index, oldIndex);        }        internal NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList newItems, IList oldItems, int newIndex, int oldIndex)        {            this._action = action;            this._newItems = ((newItems == null) ? null : ArrayList.ReadOnly(newItems));            this._oldItems = ((oldItems == null) ? null : ArrayList.ReadOnly(oldItems));            this._newStartingIndex = newIndex;            this._oldStartingIndex = oldIndex;        }        private void InitializeAddOrRemove(NotifyCollectionChangedAction action, IList changedItems, int startingIndex)        {            if (action == NotifyCollectionChangedAction.Add)            {                this.InitializeAdd(action, changedItems, startingIndex);                return;            }            if (action == NotifyCollectionChangedAction.Remove)            {                this.InitializeRemove(action, changedItems, startingIndex);            }        }        private void InitializeAdd(NotifyCollectionChangedAction action, IList newItems, int newStartingIndex)        {            this._action = action;            this._newItems = ((newItems == null) ? null : ArrayList.ReadOnly(newItems));            this._newStartingIndex = newStartingIndex;        }        private void InitializeRemove(NotifyCollectionChangedAction action, IList oldItems, int oldStartingIndex)        {            this._action = action;            this._oldItems = ((oldItems == null) ? null : ArrayList.ReadOnly(oldItems));            this._oldStartingIndex = oldStartingIndex;        }        private void InitializeMoveOrReplace(NotifyCollectionChangedAction action, IList newItems, IList oldItems, int startingIndex, int oldStartingIndex)        {            this.InitializeAdd(action, newItems, startingIndex);            this.InitializeRemove(action, oldItems, oldStartingIndex);        }    }        /// <summary>Represents the method that handles the <see cref="E:System.Collections.Specialized.INotifyCollectionChanged.CollectionChanged" /> event. </summary>    /// <param name="sender">The object that raised the event.</param>    /// <param name="e">Information about the event.</param>    [__DynamicallyInvokable]    public delegate void NotifyCollectionChangedEventHandler(object sender, NotifyCollectionChangedEventArgs e);     /// <summary>Notifies listeners of dynamic changes, such as when items get added and removed or the whole list is refreshed.</summary>    [__DynamicallyInvokable]    public interface INotifyCollectionChanged    {        /// <summary>Occurs when the collection changes.</summary>        [__DynamicallyInvokable]        event NotifyCollectionChangedEventHandler CollectionChanged;    }}