刪除toolkit:listpicker綁定的最後一個元素會拋出SelectedItem must always be set to a valid value這個異常。

目測是這段代碼的問題：

 
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private static void OnSelectedItemChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
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        {
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            ((ListPicker)o).OnSelectedItemChanged(e.OldValue, e.NewValue);
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        }
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        [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "SelectedItem", Justification = "Property name.")]
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        private void OnSelectedItemChanged(object oldValue, object newValue)
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        {
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            if (newValue != null && (null == Items || Items.Count == 0))
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            {
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                if (null == Template)
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                {
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                    // Can't set the value now; remember it for later
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                    _deferredSelectedItem = newValue;
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                    return;
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                }
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                else
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                {
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                    throw new InvalidOperationException(Properties.Resources.InvalidSelectedItem);
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                }
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            }
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            // Validate new value
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            int newValueIndex = (null != newValue) ? Items.IndexOf(newValue) : -1;
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            if ((-1 == newValueIndex) && (0 < Items.Count))
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            {
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                throw new InvalidOperationException(Properties.Resources.InvalidSelectedItem);
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            }
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            // Synchronize SelectedIndex property
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            if (!_updatingSelection)
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            {
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                _updatingSelection = true;
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                SelectedIndex = newValueIndex;
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                _updatingSelection = false;
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            }
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            // Switch to Normal mode or size for current item
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            if (ListPickerMode.Normal != ListPickerMode)
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            {
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                ListPickerMode = ListPickerMode.Normal;
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            }
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            else
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            {
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                SizeForAppropriateView(false);
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            }
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            // Fire SelectionChanged event
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            var handler = SelectionChanged;
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            if (null != handler)
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            {
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                IList removedItems = (null == oldValue) ? new object[0] : new object[] { oldValue };
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                IList addedItems = (null == newValue) ? new object[0] : new object[] { newValue };
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                handler(this, new SelectionChangedEventArgs(removedItems, addedItems));
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            }
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        }
有興趣的動手改一改