C＃WinForm DataGridView绑定列表中的列表

Question

I want to bind list (ProductList) to DataGridView, but one column is collection (Categories), but the DataGridView show "(Collection)" and not the content of List. I can't rewrite or change this ProductList class. How can i bind this Categories List column?

Here is the Binding:

dataGridView1.AutoGenerateColumns = false;
dataGridView1.ColumnCount = model.ColumnsNames.Length;
for (int i = 0; i < model.ColumnsNames.Length; i++)
{
    string columnName = model.ColumnsNames[i];
    dataGridView1.Columns[i].Name = columnName;
    dataGridView1.Columns[i].DataPropertyName = columnName;
}
dataGridView1.DataSource = model.Products;

Here is ProductModel and the data source of grid is List<Product> :

public class Product
{
    //...

    /// <summary>
    /// List of product categories names (string). 
    /// In write-mode need to pass a array of categories IDs (integer)
    /// (uses wp_set_object_terms())
    /// </summary>
    public List<object> categories { get; set; }

    // ...
}

I don't want to use sub-grid, i just want to show the property as a string in a TextBoxColumn something like this: CollectionElement1, CollectionElement2, etc.

It's not my class, actually just a reference. So I cant change it anywhere.

Answer 1

You can use CellFormatting event of DataGridView to provide a friendly representation of categories property:

void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    //Use zero based index of the cell that contains categories
    var cell= 3;

    if (e.ColumnIndex == cell && e.RowIndex >= 0)
    {
        var categories = (List<object>)dataGridView1.Rows[e.RowIndex].Cells[cell].Value;
        e.Value = string.Join(", ", categories.Select(x => x.ToString()));
    }
}

In this case, categories contains List of product categories names (string). So selecting ToString() is OK. But for a case of List<SomeClass> , you either should override ToString of SomeClass or select one of it's properties.

As another option you can shape the result of query using a new ViewModel or using anonymous type, but in the current situation which Product model doesn't belong to you and it has lot's of properties, previous solution is the most simple option.

Answer 2

Something like

dataGridView1.DataSource = (from p in model.Products 
                            select string.Join(", ", p.categories.ToArray())).ToList();