C#

"There is no recommended way to do this. The DataGridView only supports hosting a user control as an editing control when a cell is in edit mode. Regarding shared rows/cells. When a row becomes unshared the grid raises the RowUnshared event. To unshare a row, the grid calls the row's clone method which in turn clones all its cells.

For a databound grid, the cells to not get their values set since the cells do not store any data -- the underlying datasource stores the data. In the SetValue and GetValue code for a cell it checks to see if the cell/column/grid is databound and if so just retrieves or sets the value to the datasource. This is why you do not get a SetValue call with values as the grid is being displayed. The cell's GetValue method will be called as the grid is being displayed, so maybe you can use that?"

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace March17_StateTracking
{
    public partial class TBEllipse : TextBox
    {
        // necessary to define this in Component scope
        // for MouseHover and MouseLeave EventHandlers
        // to work properly
        private readonly Label tLabel;

        // expose the Label for external use
        public Label TheLabel { set; get; }

        public TBEllipse()
        {
            InitializeComponent();

            tLabel = new Label();
            TheLabel = tLabel;

            tLabel.Text = "…";

            tLabel.FlatStyle = FlatStyle.Flat;
            tLabel.BorderStyle = BorderStyle.None;
            tLabel.BackColor = Color.Gainsboro;
            tLabel.TextAlign = ContentAlignment.TopRight;
            tLabel.Margin = new Padding(0, 0, 0, 0);
            tLabel.AutoSize = true;

            Controls.Add(tLabel);
            tLabel.Left = Width - tLabel.Width;
            tLabel.Show();
            tLabel.Anchor = AnchorStyles.Right | AnchorStyles.Top | AnchorStyles.Bottom;

            tLabel.MouseClick += tLabel_MouseClick;
            tLabel.MouseHover += tLabel_MouseHover;
        }

        public TBEllipse(IContainer container)
        {
            container.Add(this);

            InitializeComponent();
        }

        private void tLabel_MouseClick(object sender, MouseEventArgs e)
        {
            tLabel.BackColor = Color.Gainsboro;
        }

        private void tLabel_MouseHover(object sender, EventArgs e)
        {
            tLabel.BackColor = Color.Lime;
        }
    }
}

private void TestTBEllipse_Click(object sender, EventArgs e)
{
    TBEllipse testTBEllipse = new TBEllipse();
    testTBEllipse.Text = "some text";
    this.Controls.Add(testTBEllipse);
    testTBEllipse.Location = new Point(400,400);
    testTBEllipse.TheLabel.Click += TheLabel_Click;
}

private void TheLabel_Click(object sender, EventArgs e)
{
    MessageBox.Show("ellipsis label clicked");
}

int buttonColumnIndex;  // to identify the button column in the CellContentClick handler

public Form1() {
  InitializeComponent();
  // add the event handlers
  dgv.CellContentClick += new DataGridViewCellEventHandler(dgv_CellContentClick);
  dgv.DataBindingComplete += new DataGridViewBindingCompleteEventHandler(dgv_DataBindingComplete);
}

private void dgv_DataBindingComplete(object sender, DataGridViewBindingCompleteEventArgs e) {
  DataGridViewButtonColumn bc = new DataGridViewButtonColumn();
  bc.Name = "ButtonColumn";
  bc.HeaderText = "";
  bc.UseColumnTextForButtonValue = true;
  bc.Text = "Edit";
  bc.AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
  buttonColumnIndex = dgv.Columns.Add(bc);
  // Column will be at the right, move to the required position
  // e.g move to left
  dgv.Columns[buttonColumnIndex].DisplayIndex = 0;
}

private void dgv_CellContentClick(object sender, DataGridViewCellEventArgs e) {
  if (e.ColumnIndex == buttonColumnIndex) {
    MessageBox.Show(String.Format("Edit button clicked on row {0}", e.RowIndex));
  }
}