Question

I am trying to put a user control, named simpleChart, into a DataGridTemplateColumn. I bind the DataGrid to an ObservableCollection<Index> (where Index is an INotifyPropertyChanged class that I created for display). But somehow, the binding cannot find the root item. To check my binding, I put a textColumn aside the templateColumn, and it works just fine. Here is the relevant code:

<Window x:Class="TechniqueAnalysis.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="" Height="549" Width="1744" 
    xmlns:diagnostics="clr-namespace:System.Diagnostics;assembly=WindowsBase"
    xmlns:local="clr-namespace:Charts"
    xmlns:simpleChart ="clr-namespace:ChartOnGird;assembly=ChartOnGird"
    WindowState="Maximized" Closing="Window_Closing">
<Grid>
<DataGrid Margin="0,60,0,0" Name="dataGridWei" CanUserResizeColumns="False"  ItemsSource="{Binding}">
<DataGridTemplateColumn Header="2 day"  Width="100">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
           <simpleChart:SimpleChart X ="{Binding Path=X1, diagnostics:PresentationTraceSources.TraceLevel=High}"/>
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTextColumn Header="Value" Binding="{Binding Path=X1, diagnostics:PresentationTraceSources.TraceLevel=High, StringFormat=N2}"/>
</DataGrid>
</Grid>
</Window>

The databinding is through background code which binds the ObservableCollection to the datagrid’s DataContext.

And I get the following output for the template column:

System.Windows.Data Warning: 58 : BindingExpression (hash=45649854): Default mode resolved to OneWay
System.Windows.Data Warning: 59 : BindingExpression (hash=45649854): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 60 : BindingExpression (hash=45649854): Attach to ChartOnGird.SimpleChart.X (hash=40977533)
System.Windows.Data Warning: 65 : BindingExpression (hash=45649854): Resolving source
System.Windows.Data Warning: 68 : BindingExpression (hash=45649854): Found data context element: SimpleChart (hash=40977533) (OK)
System.Windows.Data Warning: 76 : BindingExpression (hash=45649854): Activate with root item ''
System.Windows.Data Warning: 106 : BindingExpression (hash=45649854):   At level 0 - for String.X1 found accessor <null>
System.Windows.Data Warning: 106 : BindingExpression (hash=45649854):   At level 0 - for EnumerableCollectionView.X1 found accessor <null>
System.Windows.Data Warning: 102 : BindingExpression (hash=45649854): Replace item at level 0 with {NullDataItem}, using accessor {DependencyProperty.UnsetValue}
System.Windows.Data Warning: 78 : BindingExpression (hash=45649854): TransferValue - got raw value {DependencyProperty.UnsetValue}
System.Windows.Data Warning: 86 : BindingExpression (hash=45649854): TransferValue - using fallback/default value '9'
System.Windows.Data Warning: 87 : BindingExpression (hash=45649854): TransferValue - using final value '9'
System.Windows.Data Warning: 54 : Created BindingExpression (hash=32948864) for Binding (hash=33575416)

But for the text column, I get the following warning:

System.Windows.Data Warning: 58 : BindingExpression (hash=32948864): Default mode resolved to OneWay
System.Windows.Data Warning: 59 : BindingExpression (hash=32948864): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 60 : BindingExpression (hash=32948864): Attach to System.Windows.Controls.TextBlock.Text (hash=6303902)
System.Windows.Data Warning: 65 : BindingExpression (hash=32948864): Resolving source
System.Windows.Data Warning: 68 : BindingExpression (hash=32948864): Found data context element: TextBlock (hash=6303902) (OK)
System.Windows.Data Warning: 69 : BindingExpression (hash=32948864): DataContext is null
System.Windows.Data Warning: 63 : BindingExpression (hash=32948864): Resolve source deferred
System.Windows.Data Warning: 65 : BindingExpression (hash=8194399): Resolving source 
System.Windows.Data Warning: 68 : BindingExpression (hash=8194399): Found data context element: TextBlock (hash=33203677) (OK)
System.Windows.Data Warning: 76 : BindingExpression (hash=8194399): Activate with root item Index (hash=33903126)
System.Windows.Data Warning: 106 : BindingExpression (hash=8194399):   At level 0 - for Index.X1 found accessor RuntimePropertyInfo(X1)
System.Windows.Data Warning: 102 : BindingExpression (hash=8194399): Replace item at level 0 with Index (hash=33903126), using accessor RuntimePropertyInfo(X1)
System.Windows.Data Warning: 99 : BindingExpression (hash=8194399): GetValue at level 0 from Index (hash=33903126) using RuntimePropertyInfo(X1): '1'
System.Windows.Data Warning: 78 : BindingExpression (hash=8194399): TransferValue - got raw value '1'
System.Windows.Data Warning: 82 : BindingExpression (hash=8194399): TransferValue - implicit converter produced '1.00'
System.Windows.Data Warning: 87 : BindingExpression (hash=8194399): TransferValue - using final value '1.00'
System.Windows.Data Warning: 65 : BindingExpression (hash=32948864): Resolving source
System.Windows.Data Warning: 68 : BindingExpression (hash=32948864): Found data context element: TextBlock (hash=6303902) (OK)
System.Windows.Data Warning: 76 : BindingExpression (hash=32948864): Activate with root item Index (hash=49245678)
System.Windows.Data Warning: 105 : BindingExpression (hash=32948864):   At level 0 using cached accessor for Index.X1: RuntimePropertyInfo(X1)
System.Windows.Data Warning: 102 : BindingExpression (hash=32948864): Replace item at level 0 with Index (hash=49245678), using accessor RuntimePropertyInfo(X1)
System.Windows.Data Warning: 99 : BindingExpression (hash=32948864): GetValue at level 0 from Index (hash=49245678) using RuntimePropertyInfo(X1): '1'
System.Windows.Data Warning: 78 : BindingExpression (hash=32948864): TransferValue - got raw value '1'
System.Windows.Data Warning: 82 : BindingExpression (hash=32948864): TransferValue - implicit converter produced '1.00'
System.Windows.Data Warning: 87 : BindingExpression (hash=32948864): TransferValue - using final value '1.00'

It seems that the templatecolumn fails to find a correct root item. The question is what is a proper way to help it to find the proper one? I tried to add an RelateSource but did not figure out how. My class “Index” is under the MainWindow class. Please help me. I have spend 2 days on it. I believe I am almost there but there is just something that I cannot figure out without help.

Answer 1

I’m guessing the problem is your simpleChart UserControl. Probably you set the DataContext for this control in the wrong manner and that’s why the bindings will not find the Row.DataContext but rather the UserControl.DataContext.

Take a look at this Simple Pattern for Creating Re-useable UserControls to do it the right way.