对于当前单元格

For the current cell

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();
        Shown += Form1_Shown;
    }

    private void Form1_Shown(object sender, EventArgs e)
    {
        dataGridView1.Rows.Add(1, "Karen", "Payne");
        dataGridView1.Rows.Add(2, "Mary", "Smtim");
        dataGridView1.Rows.Add(3, "Bill", "Jones");
    }
    private void button1_Click(object sender, EventArgs e)
    {
        if (dataGridView1.CurrentRow != null && dataGridView1.CurrentRow.IsNewRow) return;
        dataGridView1.CurrentCell.Value = 0;
    }
}