WPF DataGrid Sorting - Data is visually sorted. Underlying data is not sorted

Question

Would someone be able to provide some guidance to this problem:

I have a DataGrid which is bound to a DataTable.

Relevant XAML & code:

<DataGrid Name="dataGrid1" IsReadOnly="True" ItemsSource="{Binding}" 
<DataGrid.Columns>
<DataGridTextColumn Header="Name" Binding="{Binding Path=Name}" />
<DataGridTextColumn Header="Path" Binding="{Binding Path=Path}" />
</DataGrid.Columns>


dataGrid1.DataContext = gridData.dt; // this is a DataTable with 3 columns.

The 3rd dt column is not shown on the grid. It's used as the id.

The data table is sorted on the first column and contents are displayed. The user can sort on either of Name or Path columns/headings by clicking on them and visually sorting is/displays fine. The problem is when I examine the grid's data by selecting a particular row, the DataTable's data remains unsorted.

My question, what is the best approach to update the grid's underlying data upon a user sorting on one of the columns? (This requires sorting the DataTable on the proper column)

This is what I have observed:

Adding a Click event handler on DataGridColumnHeader does fire the event. I have observed that the value of columnHeader.SortDirection (in sender) is the CURRENT value, not the target value. Is it correct to say that a given column sort order goes through these phases: null --> ascending descending --> ascending ascending to descending

I.E. By knowing the current state, the next state is determinable.

I can place a trigger in the DataGridColumnHeader's SortDirection property looking for Ascending/Descending/null but then what? Can I execute code against this? If so, can you show me a code fragment.

I have gone through similar posts and tried to perform the following:

experimented with a CollectionViewSource by binding my DataGrid to one. As an experiment, I trapped the column header click event and forced a sorting order on the columns. This did not work. (My implementation may be wrong?)
I added SortedMemberPath= "xx" to my XAML to the specific DataGridTextColumn entries.

Any assistance greatly appreciated.

decyclone decyclone · Accepted Answer · 2012-08-16T15:18:24

Use DataGrid.Sorting event:

public class DataGrid : MultiSelector
{
    ...

    //
    // Summary:
    //     Occurs when a column is being sorted.
    public event DataGridSortingEventHandler Sorting;

    ...
}

In event handler, use e.Column property to find out which column was used to sort data:

void dataGrid1_Sorting(object sender, DataGridSortingEventArgs e)
{
    e.Column ... // TODO
}

WPF DataGrid Sorting - Data is visually sorted. Underlying data is not sorted

1 Answers