How do I bind a WPF DataGrid to a variable number of columns?

Question

My WPF application generates sets of data which may have a different number of columns each time. Included in the output is a description of each column that will be used to apply formatting. A simplified version of the output might be something like:

class Data
{
    IList<ColumnDescription> ColumnDescriptions { get; set; }
    string[][] Rows { get; set; }
}

This class is set as the DataContext on a WPF DataGrid but I actually create the columns programmatically:

for (int i = 0; i < data.ColumnDescriptions.Count; i++)
{
    dataGrid.Columns.Add(new DataGridTextColumn
    {
        Header = data.ColumnDescriptions[i].Name,
        Binding = new Binding(string.Format("[{0}]", i))
    });
}

Is there any way to replace this code with data bindings in the XAML file instead?

Answer 1

You might be able to do this with AutoGenerateColumns and a DataTemplate. I'm not positive if it would work without a lot of work, you would have to play around with it. Honestly if you have a working solution already I wouldn't make the change just yet unless there's a big reason. The DataGrid control is getting very good but it still needs some work (and I have a lot of learning left to do) to be able to do dynamic tasks like this easily.

Answer 2

I've continued my research and have not found any reasonable way to do this. The Columns property on the DataGrid isn't something I can bind against, in fact it's read only.

Bryan suggested something might be done with AutoGenerateColumns so I had a look. It uses simple .Net reflection to look at the properties of the objects in ItemsSource and generates a column for each one. Perhaps I could generate a type on the fly with a property for each column but this is getting way off track.

Since this problem is so easily sovled in code I will stick with a simple extension method I call whenever the data context is updated with new columns:

public static void GenerateColumns(this DataGrid, IEnumerable<ColumnSchema> columns)
{
    dataGrid.Columns.Clear();

    int index = 0;
    foreach (var column in columns)
    {
        dataGrid.Columns.Add(new DataGridTextColumn
        {
            Header = column.Name,
            Binding = new Binding(string.Format("[{0}]", index++))
        });
    }
}

// E.g. myGrid.GenerateColumns(schema);

Answer 3

You can create a usercontrol with the grid definition and define 'child' controls with varied column definitions in xaml. The parent needs a dependency property for columns and a method for loading the columns:

Parent:

---

{ // public ObservableCollection gridColumns {
get { return (ObservableCollection)GetValue(ColumnsProperty); } set { SetValue(ColumnsProperty, value); }

    }

    public static readonly DependencyProperty ColumnsProperty =
    DependencyProperty.Register("gridColumns", typeof(ObservableCollection<DataGridColumn>),
        typeof(parentControl), new PropertyMetadata(new ObservableCollection<DataGridColumn>()));

public void LoadGrid() { if (gridColumns.Count > 0) myGrid.Columns.Clear();

        foreach (DataGridColumn c in gridColumns)
        {
            myGrid.Columns.Add(c);
        }
    }

Child Xaml:

---

        <local:parentControl.gridColumns>

            <toolkit:DataGridTextColumn Width="Auto" Header="Child1"   Binding="{Binding Path=.}" />
            <toolkit:DataGridTextColumn Width="Auto" Header="Child2"   Binding="{Binding Path=.}" />
        </local:parentControl.gridColumns>


    </local:parentControl>

---

And finally, the tricky part is finding where to call 'LoadGrid'. I am struggling with this but got things to work by calling after 'InitalizeComponent' in my window constructor: (childGrid is x:name in window.xaml)

childGrid.deGrid.LoadGrid();

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