Retrieving items from --- DataGridViewComboBoxColumn

Question

Suppose I have designed a DataGridView to have a comboBoxColumn named 'dataGridViewComboBocColumn'.

I can populate the comboBox using the following code:

private void DataGridViewForm_Load(object sender, EventArgs e)
    {
        BookCollection books = Book.GetAllBooks();

        foreach (Book b in books)
        {                
            dataGridViewComboBocColumn.Items.Add(b);
        }

        dataGridViewComboBocColumn.DisplayMember = "BookName";
        dataGridViewComboBocColumn.ValueMember = "BookISBN";
    }

But how can I retrieve a selected item object. So that I can cast and convert that item into a Book - object.

Answer 1

You cant :(

This is a limitation of the DataGridViewComboBoxColumn.

I worked around this by creating a TypeDescriptor that adds an extra item called 'this', that returns the instance.

Answer 2

Ok, here's a little hack you can do. First, hook into the DataGridView's EditingControlShowing event, and in the event handler the EventArgs has a property e.Control that can be cast to a standard ComboBox. So, keep a dictionary that is keyed by the int being the rowindex. Then, in the event handler, add the combo box to the dictionary:

    private Dictionary<int, ComboBox> comboBoxes;
    public Form1()
    {
        InitializeComponent();
        this.comboBoxes = new Dictionary<int, ComboBox>();
        this.dataGridView1.EditingControlShowing += new DataGridViewEditingControlShowingEventHandler(dataGridView1_EditingControlShowing);
    }

    private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
        var cb = e.Control as ComboBox;
        if (!(this.comboBoxes.ContainsKey(this.dataGridView1.CurrentRow.Index)))
        {
            this.comboBoxes.Add(this.dataGridView1.CurrentRow.Index, cb);
        }
    }

Then, when you need to get the object out of the combobox, just iterate through your dictionary, and get the right combobox, and just get the SelectedItem / SelectedValue.