using System.Diagnostics;
using System.Windows.Forms;

namespace PDP

{
    class MyDatagridView : DataGridView
    {
        protected override bool ProcessDialogKey(Keys keyData)
        {
            if (keyData == Keys.Enter)
            {
                base.ProcessTabKey(Keys.Tab);
                return true;
            }
            return base.ProcessDialogKey(keyData);
        }

        protected override bool ProcessDataGridViewKey(KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                base.ProcessTabKey(Keys.Tab);
                return true;
            }
            return base.ProcessDataGridViewKey(e);
        }
    }
}

DataGridView datagridQa = new MyDatagridView();

int columnIndex = 0;
int rowIndex = 0;
bool endEdit = false;
private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
{
     columnIndex = dataGridView1.CurrentCell.ColumnIndex;
     rowIndex = dataGridView1.CurrentCell.RowIndex;
     endEdit = true;
}

private void dataGridView1_SelectionChanged(object sender, EventArgs e)
        {
            if (dataGridView1.CurrentCell != null && endEdit)
            {
                if (columnIndex == dataGridView1.Columns.Count - 1)
                    dataGridView1.CurrentCell = dataGridView1[0, rowIndex + 1];
                else
                    dataGridView1.CurrentCell = dataGridView1[columnIndex + 1, rowIndex];
                endEdit = false;
            }

        }

private void dataGridView1_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                e.SuppressKeyPress = true;
                int columnIndex = dataGridView1.CurrentCell.ColumnIndex;
                int rowIndex = dataGridView1.CurrentCell.RowIndex;
                if (columnIndex == dataGridView1.Columns.Count - 1)
                    dataGridView1.CurrentCell = dataGridView1[0, rowIndex + 1];
                else
                    dataGridView1.CurrentCell = dataGridView1[columnIndex + 1, rowIndex];
            }
            if (e.KeyCode == Keys.Tab)
            {
                e.Handled = true;
            }
        }

private void DataGridView1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.Enter)
    {
        e.SuppressKeyPress = true;
        SendKeys.Send("{TAB}");
    }
}