Question

Is it possible to allow more than one object in a cell in a DataGridView?

I want to display a Group in the first column and then in the column next to it I want to display all of the users that are in that group but in one cell (the cell next to the group name). And this can not be string manipulation because I need to be able to click on each of the users and drag and drop them around. I am using a DataGridview linked up to a SQL query database.

I am using Visual Basic with Visual Studio 2010.

Answer 1

Unfortunately you cannot do this in the DataGridView. You can, however, create a table that looks something like this:

GROUP   USER
------  -----

Group1  User1
Group1  User2
Group1  User3
Group2  UserA
Group2  UserB

Once you do this, then you can handle the CellFormatting event of the DataGridView and set the e.FormattedValue to String.Empty if the value of the cell above matches. Then your table will “look” like:

GROUP   USER
------  -----

Group1  User1
        User2
        User3
Group2  UserA
        UserB

This is pretty much what you are looking for. If you want the gridlines to go away, you can instead handle the DataGridView’s CellPainting event to draw proper borders, center text, etc.

UPDATE: Here’s an example of using the CellFormatting event to hide the contents of a cell. In this example, I am just using a List as my datasource, but you can substitute this for your SQL Data Source, DataTable, etc.

public partial class Form1 : Form
{
    private List<GroupUserRow> _rows = new List<GroupUserRow>();

    public Form1()
    {
        InitializeComponent();

        _rows.Add(new GroupUserRow { Group = "Group1", User = "User1" });
        _rows.Add(new GroupUserRow { Group = "Group1", User = "User2" });
        _rows.Add(new GroupUserRow { Group = "Group1", User = "User3" });
        _rows.Add(new GroupUserRow { Group = "Group2", User = "UserA" });
        _rows.Add(new GroupUserRow { Group = "Group2", User = "UserB" });

        dataGridView1.DataSource = _rows;
    }

    private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
    {
        if (e.RowIndex >= 0 && e.ColumnIndex == 0)
        {
            int prevRowIndex = e.RowIndex - 1;
            if (prevRowIndex >= 0 && dataGridView1[0, prevRowIndex].Value == e.Value)
            {
                //this just "hides" the value from the screen, the value is not
                //removed from the cell
                e.Value = String.Empty;
                e.FormattingApplied = true;
            }
        }
    }

    private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
    {
        if (e.RowIndex >= 0 && e.ColumnIndex >= 0)
        {
            MessageBox.Show("This cell's value is: " + dataGridView1[e.ColumnIndex, e.RowIndex].Value);
        }
    }

}

public class GroupUserRow
{
    public string Group { get; set; }
    public string User { get; set; }
}