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//---------------------------------------------------------------------
// <copyright file="ObjectView.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data.Common;
using System.Data.Metadata;
using System.Data.Metadata.Edm;
using System.Data.Objects.DataClasses;
using System.Diagnostics;
using System.Reflection;
namespace System.Data.Objects
{
/// <summary>
/// Manages a list suitable for data binding.
/// </summary>
/// <typeparam name="TElement">
/// The type of elements in the binding list.
/// </typeparam>
/// <remarks>
/// <para>
/// This class provides an implementation of IBindingList that exposes a list of elements to be bound,
/// provides a mechanism to change the membership of the list,
/// and events to notify interested objects when the membership of the list is modified
/// or an element in the list is modified.
/// </para>
/// <para>
/// ObjectView relies on an object that implements IObjectViewData to manage the binding list.
/// See the documentation for IObjectViewData for details.
/// </para>
/// </remarks>
internal class ObjectView<TElement> : IBindingList, ICancelAddNew, IObjectView
{
/// <summary>
/// Specifies whether events handled from an underlying collection or individual bound item
/// should result in list change events being fired from this IBindingList.
/// <b>True</b> to prevent events from being fired from this IBindingList;
/// otherwise <b>false</b> to allow events to propogate.
/// </summary>
private bool _suspendEvent;
// Delegate for IBindingList.ListChanged event.
private ListChangedEventHandler onListChanged;
/// <summary>
/// Object that listens for underlying collection or individual bound item changes,
/// and notifies this object when they occur.
/// </summary>
private ObjectViewListener _listener;
/// <summary>
/// Index of last item added via a call to IBindingList.AddNew.
/// </summary>
private int _addNewIndex = -1;
/// <summary>
/// Object that maintains the underlying bound list,
/// and specifies the operations allowed on that list.
/// </summary>
private IObjectViewData<TElement> _viewData;
/// <summary>
/// Construct a new instance of ObjectView using the supplied IObjectViewData and event data source.
/// </summary>
/// <param name="viewData">
/// Object that maintains the underlying bound list,
/// and specifies the operations allowed on that list.
/// </param>
/// <param name="eventDataSource">
/// Event source to "attach" to in order to listen to collection and item changes.
/// </param>
internal ObjectView(IObjectViewData<TElement> viewData, object eventDataSource)
{
_viewData = viewData;
_listener = new ObjectViewListener(this, (IList)_viewData.List, eventDataSource);
}
private void EnsureWritableList()
{
if (((IList)this).IsReadOnly)
{
throw EntityUtil.WriteOperationNotAllowedOnReadOnlyBindingList();
}
}
private bool IsElementTypeAbstract
{
get { return typeof(TElement).IsAbstract; }
}
#region ICancelAddNew implementation
/// <summary>
/// If a new item has been added to the list, and <paramref name="itemIndex"/> is the position of that item,
/// remove it from the list and cancel the add operation.
/// </summary>
/// <param name="itemIndex">Index of item to be removed as a result of the cancellation of a previous addition.</param>
void ICancelAddNew.CancelNew(int itemIndex)
{
if (_addNewIndex >= 0 && itemIndex == _addNewIndex)
{
TElement item = _viewData.List[_addNewIndex];
_listener.UnregisterEntityEvents(item);
int oldIndex = _addNewIndex;
// Reset the addNewIndex here so that the IObjectView.CollectionChanged method
// will not attempt to examine the item being removed.
// See IObjectView.CollectionChanged method for details.
_addNewIndex = -1;
try
{
_suspendEvent = true;
_viewData.Remove(item, true);
}
finally
{
_suspendEvent = false;
}
OnListChanged(ListChangedType.ItemDeleted, oldIndex, -1);
}
}
/// <summary>
/// Commit a new item to the binding list.
/// </summary>
/// <param name="itemIndex">
/// Index of item to be committed.
/// This index must match the index of the item created by the last call to IBindindList.AddNew;
/// otherwise this method is a nop.
/// </param>
void ICancelAddNew.EndNew(int itemIndex)
{
if (_addNewIndex >= 0 && itemIndex == _addNewIndex)
{
_viewData.CommitItemAt(_addNewIndex);
_addNewIndex = -1;
}
}
#endregion
#region IBindingList implementation
bool IBindingList.AllowNew
{
get { return _viewData.AllowNew && !IsElementTypeAbstract; }
}
bool IBindingList.AllowEdit
{
get { return _viewData.AllowEdit; }
}
object IBindingList.AddNew()
{
EnsureWritableList();
if (IsElementTypeAbstract)
{
throw EntityUtil.AddNewOperationNotAllowedOnAbstractBindingList();
}
_viewData.EnsureCanAddNew();
((ICancelAddNew)this).EndNew(_addNewIndex);
TElement newItem = (TElement)Activator.CreateInstance(typeof(TElement));
_addNewIndex = _viewData.Add(newItem, true);
_listener.RegisterEntityEvents(newItem);
OnListChanged(ListChangedType.ItemAdded, _addNewIndex /* newIndex*/, -1 /*oldIndex*/);
return newItem;
}
bool IBindingList.AllowRemove
{
get { return _viewData.AllowRemove; }
}
bool IBindingList.SupportsChangeNotification
{
get { return true; }
}
bool IBindingList.SupportsSearching
{
get { return false; }
}
bool IBindingList.SupportsSorting
{
get { return false; }
}
bool IBindingList.IsSorted
{
get { return false; }
}
PropertyDescriptor IBindingList.SortProperty
{
get { throw EntityUtil.NotSupported(); }
}
ListSortDirection IBindingList.SortDirection
{
get { throw EntityUtil.NotSupported(); }
}
public event System.ComponentModel.ListChangedEventHandler ListChanged
{
add
{
onListChanged += value;
}
remove
{
onListChanged -= value;
}
}
void IBindingList.AddIndex(PropertyDescriptor property)
{
throw EntityUtil.NotSupported();
}
void IBindingList.ApplySort(PropertyDescriptor property, ListSortDirection direction)
{
throw EntityUtil.NotSupported();
}
int IBindingList.Find(PropertyDescriptor property, object key)
{
throw EntityUtil.NotSupported();
}
void IBindingList.RemoveIndex(PropertyDescriptor property)
{
throw EntityUtil.NotSupported();
}
void IBindingList.RemoveSort()
{
throw EntityUtil.NotSupported();
}
#endregion
/// <summary>
/// Get item at the specified index.
/// </summary>
/// <param name="index">
/// The zero-based index of the element to get or set.
/// </param>
/// <remarks>
/// This strongly-typed indexer is used by the data binding in WebForms and ASP.NET
/// to determine the Type of elements in the bound list.
/// The list of properties available for binding can then be determined from that element Type.
/// </remarks>
public TElement this[int index]
{
get
{
return _viewData.List[index];
}
set
{
// this represents a ROW basically whole entity, we should not allow any setting
throw EntityUtil.CannotReplacetheEntityorRow();
}
}
#region IList implementation
object IList.this[int index]
{
get
{
return _viewData.List[index];
}
set
{
// this represents a ROW basically whole entity, we should not allow any setting
throw EntityUtil.CannotReplacetheEntityorRow();
}
}
bool IList.IsReadOnly
{
get
{
return !(_viewData.AllowNew || _viewData.AllowRemove);
}
}
bool IList.IsFixedSize
{
get { return (false); }
}
int IList.Add(object value)
{
EnsureWritableList();
EntityUtil.CheckArgumentNull(value, "value");
if (!(value is TElement))
{
throw EntityUtil.IncompatibleArgument();
}
((ICancelAddNew)this).EndNew(_addNewIndex);
int index = ((IList)this).IndexOf(value);
// Add the item if it doesn't already exist in the binding list.
if (index == -1)
{
index = _viewData.Add((TElement)value, false);
// Only fire a change event if the IObjectView data doesn't implicitly fire an event itself.
if (!_viewData.FiresEventOnAdd)
{
_listener.RegisterEntityEvents(value);
OnListChanged(ListChangedType.ItemAdded, index /*newIndex*/, -1/* oldIndex*/);
}
}
return index;
}
void IList.Clear()
{
EnsureWritableList();
((ICancelAddNew)this).EndNew(_addNewIndex);
// Only fire a change event if the IObjectView data doesn't implicitly fire an event itself.
if (_viewData.FiresEventOnClear)
{
_viewData.Clear();
}
else
{
try
{
// Suspend list changed events during the clear, since the IObjectViewData declared that it wouldn't fire an event.
// It's possible the IObjectViewData could implement Clear by repeatedly calling Remove,
// and we don't want these events to percolate during the Clear operation.
_suspendEvent = true;
_viewData.Clear();
}
finally
{
_suspendEvent = false;
}
OnListChanged(ListChangedType.Reset, -1 /*newIndex*/, -1/* oldIndex*/); // Indexes not used for reset event.
}
}
bool IList.Contains(object value)
{
bool itemExists;
if (value is TElement)
{
itemExists = _viewData.List.Contains((TElement)value);
}
else
{
itemExists = false;
}
return itemExists;
}
int IList.IndexOf(object value)
{
int index;
if (value is TElement)
{
index = _viewData.List.IndexOf((TElement)value);
}
else
{
index = -1;
}
return index;
}
void IList.Insert(int index, object value)
{
throw EntityUtil.IndexBasedInsertIsNotSupported();
}
void IList.Remove(object value)
{
EnsureWritableList();
EntityUtil.CheckArgumentNull(value, "value");
if (!(value is TElement))
{
throw EntityUtil.IncompatibleArgument();
}
Debug.Assert(((IList)this).Contains(value), "Value does not exist in view.");
((ICancelAddNew)this).EndNew(_addNewIndex);
TElement item = (TElement)value;
int index = _viewData.List.IndexOf(item);
bool removed = _viewData.Remove(item, false);
// Only fire a change event if the IObjectView data doesn't implicitly fire an event itself.
if (removed && !_viewData.FiresEventOnRemove)
{
_listener.UnregisterEntityEvents(item);
OnListChanged(ListChangedType.ItemDeleted, index /* newIndex */, -1 /* oldIndex */);
}
}
void IList.RemoveAt(int index)
{
((IList)this).Remove(((IList)this)[index]);
}
#endregion
#region ICollection implementation
public int Count
{
get { return _viewData.List.Count; }
}
public void CopyTo(Array array, int index)
{
((IList)_viewData.List).CopyTo(array, index);
}
object ICollection.SyncRoot
{
get { return this; }
}
bool ICollection.IsSynchronized
{
get { return false; }
}
public IEnumerator GetEnumerator()
{
return _viewData.List.GetEnumerator();
}
#endregion
private void OnListChanged(ListChangedType listchangedType, int newIndex, int oldIndex)
{
ListChangedEventArgs changeArgs = new ListChangedEventArgs(listchangedType, newIndex, oldIndex);
OnListChanged(changeArgs);
}
private void OnListChanged(ListChangedEventArgs changeArgs)
{
// Only fire the event if someone listens to it and it is not suspended.
if (onListChanged != null && !_suspendEvent)
{
onListChanged(this, changeArgs);
}
}
void IObjectView.EntityPropertyChanged(object sender, PropertyChangedEventArgs e)
{
Debug.Assert(sender is TElement, "Entity should be of type TElement");
int index = ((IList)this).IndexOf((TElement)sender);
OnListChanged(ListChangedType.ItemChanged, index /*newIndex*/, index/*oldIndex*/);
}
/// <summary>
/// Handle a change in the underlying collection bound by this ObjectView.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">
/// Event arguments that specify the type of modification and the associated item.
/// </param>
void IObjectView.CollectionChanged(object sender, CollectionChangeEventArgs e)
{
// If there is a pending edit of a new item in the bound list (indicated by _addNewIndex >= 0)
// and the collection membership changed due to an operation external to this ObjectView,
// it is possible that the _addNewIndex position will need to be adjusted.
//
// If the modification was made through this ObjectView, the pending edit would have been implicitly committed,
// and there would be no need to examine it here.
TElement addNew = default(TElement);
if (_addNewIndex >= 0)
{
addNew = this[_addNewIndex];
}
ListChangedEventArgs changeArgs = _viewData.OnCollectionChanged(sender, e, _listener);
if (_addNewIndex >= 0)
{
if (_addNewIndex >= this.Count)
{
_addNewIndex = ((IList)this).IndexOf(addNew);
}
else if (!this[_addNewIndex].Equals(addNew))
{
_addNewIndex = ((IList)this).IndexOf(addNew);
}
}
if (changeArgs != null)
{
OnListChanged(changeArgs);
}
}
}
}
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