WPF: How to get name or other unique identifier of calling object in event handler for serialization?

Question

I have a GridView and want to serialize column widths across sessions. My idea of how to accomplish this is to attach a behavior to the GridViewColumns in such a way that each time the width of a column is changed the attached event handler is called and stores the new width. This already works well.

The only remaining problem:

How do I know in the event handler which GridViewColumn sent the event? I obviously need to know that in order to be able to store the width and later set the width on the correct column when restoring. Ideally I would like to use the name specified in XAML as column identifier.

Here is my code. XAML:

<GridView>
  <GridViewColumn x:Name="GridColumn0"
    HeaderTemplate="{StaticResource GridViewHeaderTemplate}" HeaderContainerStyle="{StaticResource GridViewHeaderStyle}" 
    Header="{x:Static strings:Strings.MainWindow_AppLog_Header_Severity}"
    behaviors:GridViewBehaviors.PersistColumnWidth="True">

C# (please scroll down - question at bottom):

// Register the property used in XAML
public static readonly DependencyProperty PersistColumnWidthProperty =
     DependencyProperty.RegisterAttached("PersistColumnWidth", typeof(bool), typeof(GridViewBehaviors),
     new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnPersistColumnWidthChanged)));

// Provide read access to the value
public static bool GetPersistColumnWidth(DependencyObject d)
{
    return (bool)d.GetValue(PersistColumnWidthProperty);
}

// Provide write access to the value (set from XAML)
public static void SetPersistColumnWidth(DependencyObject d, bool value)
{
    d.SetValue(PersistColumnWidthProperty, value);
}

// This gets called once when the XAML is compiled to BAML
// Set the event handler
private static void OnPersistColumnWidthChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
    GridViewColumn column = sender as GridViewColumn;
    if (column == null)
        return;

    // Couple the UI event with a delegate
    if ((bool)args.NewValue)
        ((INotifyPropertyChanged)column).PropertyChanged += new PropertyChangedEventHandler(PersistWidth);
    else
        ((INotifyPropertyChanged)column).PropertyChanged -= new PropertyChangedEventHandler(PersistWidth);
}

// Deal with the events
static void PersistWidth(object sender, PropertyChangedEventArgs e)
{
    GridViewColumn column = sender as GridViewColumn;
    if (column == null)
        return;

    // We are only interested in changes of the "ActualWidth" property
    if (e.PropertyName != "ActualWidth")
        return;

    // Ignore NaNs
    if (column.ActualWidth == double.NaN)
        return;

    // Persist the width here
    // PROBLEM:
    // How to get a unique identifier for column, ideally its name set in XAML?
}

score 3 · Answer 1 · answered Jan 06 '11 at 20:43

3

I don't think you will be able to access the x:Name, but you should be able to define your own column type that has a Name property that you can set.

So instead of adding GridViewColumns you add NamedColumn objects in your xaml.

Define a type that derives from GridViewColumn:

public class NamedColumn : GridViewColumn
{
   public string ColumnName {get; set;}
}

And use it in your xaml:

<GridView>
  <NamedColumn ColumnName="GridColumn0" .... blablalba more stuff here />
  ...

NoW you should be able to cast the sender to a NamedColumn and access its name property.

answered Jan 06 '11 at 20:43

Rune Grimstad

35,612
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Not a perfect option, but I think it is the closest you get. – Rune Grimstad Jan 06 '11 at 20:47
Nice, but I think I found something even easier for my situation. Please see my answer below. – Helge Klein Jan 06 '11 at 21:16

score 1 · Answer 2 · edited May 23 '17 at 11:55

1

can you use column.Header.ToString()? see here for why name from XAML isn't possible: How to get x:Name value runtime

edited May 23 '17 at 11:55

Community

1
1

answered Jan 06 '11 at 20:38

Robert Levy

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column.Header.ToString() yields "Type" :( – Helge Klein Jan 06 '11 at 20:45
+1 for the link that pointed me to the solution (see my answer) – Helge Klein Jan 06 '11 at 21:22

score 1 · Accepted Answer · edited May 23 '17 at 12:04

Thanks for your answers, Robert, Thomas and Rune. I like Runes answer, but I found something even easier for my situation here:

I changed the type of the attached property from bool to string and simply store the name of the column there. The relevant changes are below.

XAML:

<GridViewColumn 
  behaviors:GridViewBehaviors.PersistColumnWidth="MainWindow_AppLog_Column0">

C#:

public static readonly DependencyProperty PersistColumnWidthProperty = 
  DependencyProperty.RegisterAttached("PersistColumnWidth", typeof(string),
  typeof(GridViewBehaviors), new FrameworkPropertyMetadata(string.Empty, 
  new PropertyChangedCallback(OnPersistColumnWidthChanged)));

static void PersistWidth(object sender, PropertyChangedEventArgs e)
{
  // This now yields "MainWindow_AppLog_Column0"
  string columnID = GetPersistColumnWidth(column);

Good idea! Really like it :-) – Rune Grimstad Jan 07 '11 at 07:11 — Rune Grimstad, Jan 07 '11 at 07:11

score 0 · Answer 4 · answered Jan 06 '11 at 20:45

I'm not sure it would work, but you can try something like that:

INameScope nameScope = NameScope.GetNameScope(column);
string name = nameScope
               .Where(kvp => kvp.Value == column)
               .Select(kvp => kvp.Key.ToString())
               .FirstOrDefault();

WPF: How to get name or other unique identifier of calling object in event handler for serialization?

4 Answers4