At work, we are using the Infragistics .NET Advantage for WPF, one control of which is the xamDataGrid. We had a small requirement that was to show a label over the grid whenever no records were obtained for the xamDataGrid.DataSource.
Now I could have tackled this in a simple manner where I placed the xamDataGrid in a Grid along with a Label both with Margin=”0″, and both with HorizontalAlignment=”Stretch” and VerticalAlignment=”Stretch”, and then set the label visibility either in code behind or using a special ValueConverter. But where would be the fun/elegance in that?
So what I decided to do was create a special AdornerDecorator and a special Adorner to do the job.
The AdornerDecorator (DataGridRecordAdornerDecorator) that I wrote allows you to bind a RecordCount DependencyProperty to the source xamDataGrid.Records.Count , and from there the DataGridRecordAdornerDecorator is self managing, and will either show a message (which can be set via the Prompt CLR property).
It's fairly easy to setup here is the most important part of the XAML for the Window that contains the xamDataGrid:
1: <Grid Background="Gray" Margin="0″>
2: <igDP:XamDataGrid x:Name="XamDataGrid1″
3: Theme="Onyx"
4: Margin="0″
5: HorizontalAlignment="Stretch"
6: VerticalAlignment="Stretch"
7: DataSource=
8: "{Binding
9: Source={StaticResource
10: BookData},XPath=Book}">
11: </igDP:XamDataGrid>
12:
13: <local:DataGridRecordAdornerDecorator
14: Prompt="GRRR, Why no stuff"
15: RecordCount="{Binding
16: ElementName=XamDataGrid1,
17: Path=Records.Count}"/>
18:
19: </Grid>
Where I am simply toggling the DataSource to a small XML data island or to null, in code behind. Here is the code to do this, this is just test code, you SHOULD NOT use this code, it is just to demonstrate the attached demo app.
1: private void btnToggle_Click(object sender, RoutedEventArgs e)
2: {
3: if (zeroTheDataSource)
4: {
5: XamDataGrid1.DataSource = null;
6: }
7: else
8: {
9: Binding b = new Binding();
10: b.Source = this.TryFindResource("BookData")
11: as XmlDataProvider;
12: b.XPath = "Book";
13: XamDataGrid1.SetBinding(
14: XamDataGrid.DataSourceProperty, b);
15: }
16: zeroTheDataSource = !zeroTheDataSource;
17: MessageBox.Show(XamDataGrid1.
Records.Count.ToString());
18:
19: }
So how does the DataGridRecordAdornerDecorator work, well it's actually very simple. It simply shows/hides a specialized Adorner (DataGridRecordAdorner) based on the current value of the RecordCount DependencyProperty. Here is the code:
1: using System;
2: using System.Windows;
3: using System.Windows.Documents;
4:
5: namespace WpfApplication1
6: {
7: public class DataGridRecordAdornerDecorator
: AdornerDecorator
8: {
9: #region Data
10: private AdornerLayer layer = null;
11: private DataGridRecordAdorner adorner = null;
12: private FrameworkElement adornedElement;
13: private String prompt = "No RECORDS FOUND";
14: #endregion
15:
16: #region Ctor
17: public DataGridRecordAdornerDecorator()
18: {
19: this.Loaded +=
20: new RoutedEventHandler(
21: DataGridRecordAdornerDecorator_Loaded);
22: }
23: #endregion
24:
25: #region Public Properties
26:
27:
28: public String Prompt
29: {
30: get { return prompt;}
31: set { prompt = value;}
32: }
33:
34:
35: /// <summary>
36: /// RecordCount Dependency Property
37: /// </summary>
38: public static readonly DependencyProperty RecordCountProperty =
39: DependencyProperty.Register("RecordCount", typeof(Int32),
40: typeof(DataGridRecordAdornerDecorator),
41: new FrameworkPropertyMetadata((Int32)0,
42: new PropertyChangedCallback(OnRecordCountChanged)));
43:
44: /// <summary>
45: /// Gets or sets the RecordCount property.
46: /// </summary>
47: public Int32 RecordCount
48: {
49: get { return (Int32)GetValue(RecordCountProperty); }
50: set { SetValue(RecordCountProperty, value); }
51: }
52:
53: /// <summary>
54: /// Handles changes to the RecordCount property.
55: /// </summary>
56: private static void OnRecordCountChanged(DependencyObject d,
57: DependencyPropertyChangedEventArgs e)
58: {
59: DataGridRecordAdornerDecorator me =
60: (DataGridRecordAdornerDecorator)d;
61:
62: Int32 value = 0;
63: Int32.TryParse(e.NewValue.ToString(), out value);
64:
65: if (value == 0)
66: {
67: me.adorner = new DataGridRecordAdorner(
68: me.adornedElement, me.Prompt);
69: me.layer.Add(me.adorner);
70: }
71: else
72: {
73: if (me.adorner != null &&
74: me.layer != null)
75: {
76: me.layer.Remove(me.adorner);
77: me.adorner = null;
78: }
79: }
80: }
81: #endregion
82:
83: #region Private Methods
84:
85: private void DataGridRecordAdornerDecorator_Loaded(
86: object sender, RoutedEventArgs e)
87: {
88: layer = this.AdornerLayer;
89: adornedElement = new FrameworkElement {
90: Height = this.Height, Width = this.Width };
91: this.Child = adornedElement;
92:
93:
94: }
95: #endregion
96:
97: #region Overrides
98: protected override void OnRenderSizeChanged(
99: System.Windows.SizeChangedInfo sizeInfo)
100: {
101: base.OnRenderSizeChanged(sizeInfo);
102:
103: if (adornedElement != null)
104: {
105: adornedElement.Height = sizeInfo.NewSize.Height;
106: adornedElement.Width = sizeInfo.NewSize.Width;
107: }
108:
109: }
110: #endregion
111: }
112: }
And here is the code for the DataGridRecordAdorner.
1: using System;
2: using System.Collections;
3: using System.Windows;
4: using System.Windows.Controls;
5: using System.Windows.Documents;
6: using System.Windows.Media;
7: using System.Collections.ObjectModel;
8:
9: namespace WpfApplication1
10: {
11: /// <summary>
12: /// Hosts an single Label in the AdornerLayer
13: /// </summary>
14: public class DataGridRecordAdorner : Adorner
15: {
16: #region Data
17: private ArrayList logicalChildren;
18: private readonly Grid host = new Grid();
19: #endregion // Data
20:
21: #region Constructor
22:
23:
24:
25: public DataGridRecordAdorner(
26: FrameworkElement adornedCtrl, String prompt)
27: : base(adornedCtrl)
28: {
29:
30: host.Width = (double)adornedCtrl.ActualWidth;
31: host.Height = (double)adornedCtrl.ActualHeight;
32: host.VerticalAlignment = VerticalAlignment.Center;
33: host.HorizontalAlignment = HorizontalAlignment.Center;
34: host.Margin = new Thickness(0);
35: Label lbl = new Label();
36: lbl.Content = prompt;
37: lbl.Foreground = Brushes.White;
38: lbl.FontSize = 14;
39: lbl.FontWeight = FontWeights.Bold;
40: lbl.VerticalAlignment = VerticalAlignment.Center;
41: lbl.HorizontalAlignment = HorizontalAlignment.Center;
42: lbl.Margin = new Thickness(0);
43: host.Children.Add(lbl);
44: base.AddLogicalChild(host);
45: base.AddVisualChild(host);
46: }
47: #endregion // Constructor
48:
49: #region Measure/Arrange
50:
51: /// <summary>
52: /// Allows the control to determine how big it wants to be.
53: /// </summary>
54: /// <param name="constraint">A limiting size for the control.</param>
55: protected override Size
56: MeasureOverride(Size constraint)
57: {
58: return constraint;
59: }
60:
61: /// <summary>
62: /// Positions and sizes the control.
63: /// </summary>
64: /// <param name="finalSize">The actual size of the control.</param>
65: protected override Size
66: ArrangeOverride(Size finalSize)
67: {
68: Rect rect = new Rect(new Point(), finalSize);
69:
70: host.Arrange(rect);
71: return finalSize;
72: }
73:
74: #endregion // Measure/Arrange
75:
76: #region Visual Children
77:
78: /// <summary>
79: /// Required for the element to be rendered.
80: /// </summary>
81: protected override int VisualChildrenCount
82: {
83: get { return 1; }
84: }
85:
86: /// <summary>
87: /// Required for the element to be rendered.
88: /// </summary>
89: protected override Visual GetVisualChild(int index)
90: {
91: if (index != 0)
92: throw new ArgumentOutOfRangeException("index");
93:
94: return host;
95: }
96:
97: #endregion // Visual Children
98:
99: #region Logical Children
100:
101: /// <summary>
102: /// Required for the displayed element to
103: /// inherit property values
104: /// from the logical tree, such as FontSize.
105: /// </summary>
106: protected override IEnumerator LogicalChildren
107: {
108: get
109: {
110: if (logicalChildren == null)
111: {
112: logicalChildren = new ArrayList();
113: logicalChildren.Add(host);
114: }
115:
116: return logicalChildren.GetEnumerator();
117: }
118: }
119:
120: #endregion // Logical Children
121: }
122: }
Here are some screen shots showing this code in action, with some records within the xamDataGrid, we see no label.
With 0 records, within the xamDataGrid, we see a label.
Finally, here is the source code.
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