将对象列表绑定到datagridview中的单元格

Question

I'm trying to represent a list of objects from my entity framework in datagridview cell.

In order for them to display I am overriding the cellFormatting event and setting the value in the cell to a list of the ids of the objects separated by commas.

Now if the user wants to edit that cell then I need to do something with the input.

The thing I thought was to override Cellparsing and in there to set the correct objects in the data structure and also make the cell display. However the cell is just blank because I can't see where to set its contents without the control throwing a cast exception. Can I call the formatting event again?

Should I just forget this approach and have another layer in the code that outputs a view that can be bound without all this to the datagrid?

Thankyou.

    private void dataGridView1_CellParsing(object sender,  DataGridViewCellParsingEventArgs e)
    {
        if (dataGridView1.Columns[e.ColumnIndex].Name == "Categories")
        {
            String catids = dataGridView1.CurrentCell.Value.ToString();

            Product p = (Product)productBS.Current;

            //DataRow dataRow = ((DataRowView)bindingSource1.Current).Row;

            p.Categories.Clear();

            String[] catstrings = catids.Split(',');

            foreach (var cs in catstrings)
            {
                int catid = 0;

                int.TryParse(cs, out catid);

                if (catid != 0)
                {
                    // Find this cat list in the BS and change it
                    p.Categories.Add(_db.Categories.Find(catid));
                }
            }

            e.Value = p.Categories;

            e.ParsingApplied = true;


        }


    }

Answer 1

(1) Do not do in cell formatting event its expensive. First format the data and then display

(2) Now if user wants edit and you want to format the data. Then use the belo event to track editing

  private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
    {
        // here check for formatting.
    }

Answer 2

If I format the data before I bind it I will have to create another object like a view of simple properties, so it's another layer of objects for all my complex entities that I will show. I can't just use a simple linq expression on them as it uses anonynous objects (any other way?) which then means those columns are read only.

Now for handling edited data I don't know what to put in endEdit. I can't get string from cell and convert back to object, it still throws invalid cast exception in pushValue part of pipeline. Where do I convert string back to object?