使用动态列将行绑定到 DataGrid

Question

I am creating a Retail Clothing POS System and am wanting to display items that are associated with a style in a specially formatted DataGrid.

Such as:

┌───────┬───┬───┬───┬───┬───┐
│ Color │ S │ M │ L │ X │ 2 │
├───────┼───┼───┼───┼───┼───┤
│ Red   │ 2 │ 2 │ 2 │ 0 │ 1 │
│ Blue  │ 0 │ 1 │ 2 │ 0 │ 0 │
│ Pink  │ 0 │ 2 │ 1 │ 1 │ 1 │
└───────┴───┴───┴───┴───┴───┘

I have the columns on the grid added at runtime based on the sizes in the style. The only issue I am having is when I try to Bind the Sizes property to a column.

private void SetColumns()
{

    ObservableCollection<DataGridColumn> columns =
        new ObservableCollection<DataGridColumn>();

    var color_col = new DataGridTextColumn()
    {
        Header = "Color",
        Binding = new Binding("Color")
    };

    columns.Add(color_col);
    if (AttributeVisible == Visibility.Visible)
    {
        columns.Add(new DataGridTextColumn()
        {
            Header = AttributeType,
            Binding = new Binding("Attribute")
        });
    }
    foreach (string s in Items.Select(i => i.Size).Distinct())
    {
        columns.Add(new DataGridTextColumn()
        {
            Header = s,
            Binding = new Binding("Sizes[0].Item2")
            //This works, for binding one Size's Quantity to all of the Columns
            //But I need something that does it for each column like a Hashmap
            //Sizes[s].Item2,
            //or a list Sizes.Where(i => i.Item1 == s).Select(i => i.Item2)
        });
    }
    ColumnCollection = new ObservableCollection<DataGridColumn>(columns);
}

The Model for the row is:

class StyleGridRow
{
    public string Color
    {
        get;
        set;
    }
    public string Attribute
    {
        get;
        set;
    }

    //The Sizes Property also contains the quantity for the size.
    /*public Hashtable Sizes
    {
        get;
        set;
    }*/

    public List<Tuple<string, int>> Sizes
    {
        get;
        set;
    }


    public StyleGridRow()
    {
        this.Color = "";
        this.Attribute = "";
        this.Sizes = new Hashtable();
    }
    public StyleGridRow(ref string Color, ref string Attribute, ref Hashtable Sizes)
    {
        this.Color = Color;
        this.Attribute = Attribute;
        this.Sizes = Sizes;
    }        
}

I have not yet figured out a way to allow the PropertyPath of the Binding to cooperate.

Is there any kind of datatype that will work for this purpose or do I need to change my StyleGridRow to better suit the design?

Answer 1

Have you tried changing the array index manually:

// Add an index to specify the array offset
int index = 0;
// The Distinct() will cause issues finding the correct array offset.
// You may need to use GroupBy() or another mechanism to group the
// column with the size.
foreach (string s in Items.Select(i => i.Size).Distinct())
{
    columns.Add(new DataGridTextColumn()
    {
        Header = s,
        // The array index must exist already. You can put a check for it above if needed.
        Binding = new Binding(string.Format("Sizes[{0}].Item2", index)),
    });
    index++;
}

EDIT: It might be better to use an ObservableCollection for the sizes. You can either use two arrays or create another class. Ideally, you would use another class and refactor the Distinct() to a higher level so all of the StyleGridRow elements have the same order and length:

// implement INPC for notifications, but I won't show it for brevity
public class SizeColumn : INotifyPropertyChanged
{
    public string Header { get; set; }
    public int Count { get; set; }
    public int Index { get; set; }
}

class StyleGridRow
{
    // ...
    public ObservableCollection<SizeColumn> SizeColumns { get; set; }
    // ...
}

// ...
int index = 0;
var sizeColumns = new List<SizeColumn>();
// TODO: Refactor `Select().Distinct()` this so all rows will have same order and length
var sizes = Items.Select(i => i.Size).Distinct().ToList();
foreach (string s in sizeColumns)
{
    // Assuming you are summing the values, and the property name is `Value`
    var count = Items.Where(x => x.Size == s).Sum(i => i.Value);
    sizeColumns.Add(new SizeColumn()
    {
        Header = s,
        Count = count,
        Index = index,
    });
    columns.Add(new DataGridTextColumn()
    {
        Header = s,
        Binding = new Binding(string.Format("SizeColumns[{0}].Count", index)),
    });
    ++index;
}
SizeColumns = new ObservableCollection<SizeColumn>(sizeColumns);
ColumnCollection = new ObservableCollection<DataGridColumn>(columns);