int currentRowIndex;
    private void dataGridView1_CellMouseUp(object sender,DataGridViewCellMouseEventArgs e)
    {
        currentRowIndex = e.RowIndex;
    }  
    private void deleteToolStripMenuItem_Click(object sender,EventArgs e)
    {    
        dataGridView1.Rows.Remove(dataGridView1.Rows[currentRowIndex]);
    }