WPF MVVM: comment lier GridViewColumn à ViewModel-Collection?

J'ai pris L'excellente solution de Thomas Levesque et l'ai modifié pour supprimer la collection statique de GridViews et aussi ajouter la capacité de définir une largeur de colonne et le format de chaîne, donc pensé que je partagerais mon code.

Modifié attachés à la propriété de la classe:

public static class GridViewColumnCollection
{
    public static readonly DependencyProperty ColumnCollectionBehaviourProperty =
        DependencyProperty.RegisterAttached("ColumnCollectionBehaviour", typeof(GridViewColumnCollectionBehaviour), typeof(GridViewColumnCollection), new UIPropertyMetadata(null));

    public static readonly DependencyProperty ColumnsSourceProperty =
        DependencyProperty.RegisterAttached("ColumnsSource", typeof(object), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.ColumnsSourceChanged));

    public static readonly DependencyProperty DisplayMemberFormatMemberProperty =
        DependencyProperty.RegisterAttached("DisplayMemberFormatMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.DisplayMemberFormatMemberChanged));

    public static readonly DependencyProperty DisplayMemberMemberProperty =
        DependencyProperty.RegisterAttached("DisplayMemberMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.DisplayMemberMemberChanged));

    public static readonly DependencyProperty HeaderTextMemberProperty =
        DependencyProperty.RegisterAttached("HeaderTextMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.HeaderTextMemberChanged));

    public static readonly DependencyProperty WidthMemberProperty =
        DependencyProperty.RegisterAttached("WidthMember", typeof(string), typeof(GridViewColumnCollection), new UIPropertyMetadata(null, GridViewColumnCollection.WidthMemberChanged));

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static GridViewColumnCollectionBehaviour GetColumnCollectionBehaviour(DependencyObject obj)
    {
        return (GridViewColumnCollectionBehaviour)obj.GetValue(ColumnCollectionBehaviourProperty);
    }

    public static void SetColumnCollectionBehaviour(DependencyObject obj, GridViewColumnCollectionBehaviour value)
    {
        obj.SetValue(ColumnCollectionBehaviourProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static object GetColumnsSource(DependencyObject obj)
    {
        return (object)obj.GetValue(ColumnsSourceProperty);
    }

    public static void SetColumnsSource(DependencyObject obj, object value)
    {
        obj.SetValue(ColumnsSourceProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetDisplayMemberFormatMember(DependencyObject obj)
    {
        return (string)obj.GetValue(DisplayMemberFormatMemberProperty);
    }

    public static void SetDisplayMemberFormatMember(DependencyObject obj, string value)
    {
        obj.SetValue(DisplayMemberFormatMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetDisplayMemberMember(DependencyObject obj)
    {
        return (string)obj.GetValue(DisplayMemberMemberProperty);
    }

    public static void SetDisplayMemberMember(DependencyObject obj, string value)
    {
        obj.SetValue(DisplayMemberMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetHeaderTextMember(DependencyObject obj)
    {
        return (string)obj.GetValue(HeaderTextMemberProperty);
    }

    public static void SetHeaderTextMember(DependencyObject obj, string value)
    {
        obj.SetValue(HeaderTextMemberProperty, value);
    }

    [AttachedPropertyBrowsableForType(typeof(GridView))]
    public static string GetWidthMember(DependencyObject obj)
    {
        return (string)obj.GetValue(WidthMemberProperty);
    }

    public static void SetWidthMember(DependencyObject obj, string value)
    {
        obj.SetValue(WidthMemberProperty, value);
    }

    private static void ColumnsSourceChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).ColumnsSource = e.NewValue;
    }

    private static void DisplayMemberFormatMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).DisplayMemberFormatMember = e.NewValue as string;
    }

    private static void DisplayMemberMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).DisplayMemberMember = e.NewValue as string;
    }

    private static void HeaderTextMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).HeaderTextMember = e.NewValue as string;
    }

    private static void WidthMemberChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        GridViewColumnCollection.GetOrCreateColumnCollectionBehaviour(sender).WidthMember = e.NewValue as string;
    }

    private static GridViewColumnCollectionBehaviour GetOrCreateColumnCollectionBehaviour(DependencyObject source)
    {
        GridViewColumnCollectionBehaviour behaviour = GetColumnCollectionBehaviour(source);

        if (behaviour == null)
        {
            GridView typedSource = source as GridView;

            if (typedSource == null)
            {
                throw new Exception("This property can only be set on controls deriving GridView");
            }

            behaviour = new GridViewColumnCollectionBehaviour(typedSource);

            SetColumnCollectionBehaviour(typedSource, behaviour);
        }

        return behaviour;
    }
}

comportement (ce qui est stocké contre chaque GridView et évite la nécessité de stocker les mappages collection-GridView au niveau central):

public class GridViewColumnCollectionBehaviour
{
    private object columnsSource;
    private GridView gridView;

    public GridViewColumnCollectionBehaviour(GridView gridView)
    {
        this.gridView = gridView;
    }

    public object ColumnsSource
    {
        get { return this.columnsSource; }
        set
        {
            object oldValue = this.columnsSource;
            this.columnsSource = value;
            this.ColumnsSourceChanged(oldValue, this.columnsSource);
        }
    }

    public string DisplayMemberFormatMember { get; set; }

    public string DisplayMemberMember { get; set; }

    public string HeaderTextMember { get; set; }

    public string WidthMember { get; set; }

    private void AddHandlers(ICollectionView collectionView)
    {
        collectionView.CollectionChanged += this.ColumnsSource_CollectionChanged;
    }

    private void ColumnsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        ICollectionView view = sender as ICollectionView;

        if (this.gridView == null)
        {
            return;
        }

        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Add:
                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = CreateColumn(e.NewItems[i]);
                    gridView.Columns.Insert(e.NewStartingIndex + i, column);
                }
                break;
            case NotifyCollectionChangedAction.Move:
                List<GridViewColumn> columns = new List<GridViewColumn>();

                for (int i = 0; i < e.OldItems.Count; i++)
                {
                    GridViewColumn column = gridView.Columns[e.OldStartingIndex + i];
                    columns.Add(column);
                }

                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = columns[i];
                    gridView.Columns.Insert(e.NewStartingIndex + i, column);
                }
                break;
            case NotifyCollectionChangedAction.Remove:
                for (int i = 0; i < e.OldItems.Count; i++)
                {
                    gridView.Columns.RemoveAt(e.OldStartingIndex);
                }
                break;
            case NotifyCollectionChangedAction.Replace:
                for (int i = 0; i < e.NewItems.Count; i++)
                {
                    GridViewColumn column = CreateColumn(e.NewItems[i]);

                    gridView.Columns[e.NewStartingIndex + i] = column;
                }
                break;
            case NotifyCollectionChangedAction.Reset:
                gridView.Columns.Clear();
                CreateColumns(sender as ICollectionView);
                break;
            default:
                break;
        }
    }

    private void ColumnsSourceChanged(object oldValue, object newValue)
    {
        if (this.gridView != null)
        {
            gridView.Columns.Clear();

            if (oldValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(oldValue);

                if (view != null)
                {
                    this.RemoveHandlers(view);
                }
            }

            if (newValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(newValue);

                if (view != null)
                {
                    this.AddHandlers(view);

                    this.CreateColumns(view);
                }
            }
        }
    }

    private GridViewColumn CreateColumn(object columnSource)
    {
        GridViewColumn column = new GridViewColumn();

        if (!string.IsNullOrEmpty(this.HeaderTextMember))
        {
            column.Header = GetPropertyValue(columnSource, this.HeaderTextMember);
        }

        if (!string.IsNullOrEmpty(this.DisplayMemberMember))
        {
            string propertyName = GetPropertyValue(columnSource, this.DisplayMemberMember) as string;

            string format = null;

            if (!string.IsNullOrEmpty(this.DisplayMemberFormatMember))
            {
                format = GetPropertyValue(columnSource, this.DisplayMemberFormatMember) as string;
            }

            if (string.IsNullOrEmpty(format))
            {
                format = "{0}";
            }

            column.DisplayMemberBinding = new Binding(propertyName) { StringFormat = format };
        }

        if (!string.IsNullOrEmpty(this.WidthMember))
        {
            double width = (double)GetPropertyValue(columnSource, this.WidthMember);
            column.Width = width;
        }

        return column;
    }

    private void CreateColumns(ICollectionView collectionView)
    {
        foreach (object item in collectionView)
        {
            GridViewColumn column = this.CreateColumn(item);

            this.gridView.Columns.Add(column);
        }
    }

    private object GetPropertyValue(object obj, string propertyName)
    {
        object returnVal = null;

        if (obj != null)
        {
            PropertyInfo prop = obj.GetType().GetProperty(propertyName);

            if (prop != null)
            {
                returnVal = prop.GetValue(obj, null);
            }
        }

        return returnVal;
    }

    private void RemoveHandlers(ICollectionView collectionView)
    {
        collectionView.CollectionChanged -= this.ColumnsSource_CollectionChanged;
    }
}

je pense que ce code serait la cause de certains problèmes de fuite de mémoire; Que votre classe GridViewColumns décrit, vous avez défini un dictionnaire statique "_gridViewsByColumnsSource" dans lequel contient le gridviews et leurs colonnes de la source de références; c'est donc une référence forte à l'ajout gridviews et les colonnes de la source; Parce que ce dictionnaire est statique, il semble qu'il y a un point de référence fixe "point" à la gridviews et les colonnes de la source de données tout le temps, si l'écran dans lequel le gridview défini fermé, le gridview ne peut pas être collecté par GC si GC est lancé; comme de plus en plus d'écrans similaires ouverts, gridviews de plus en plus et ses colonnes de données source ne peut pas être collecté, il y aura une fuite de mémoire à la fin.