form2调用form1自定义函数的问题

//form1

private void Form1_Load(object sender, EventArgs e)

        {

            loadfromtfctable();

        }



public void loadfromtfctable()

        {

            dataGridView1.DataSource =0;

            string connstr = "Data Source=MICROSOF-602800\\SQLEXPRESS;Initial Catalog=tfc;Integrated Security=True";

            string commstr = "select * from tfctable";

            SqlConnection conn = new SqlConnection(connstr);

            SqlCommand comm = new SqlCommand(commstr, conn);

            conn.Open();

            SqlDataAdapter da = new SqlDataAdapter(comm);

            DataTable dt = new DataTable();

            da.Fill(dt);

            dataGridView1.DataSource = dt;

            conn.Close();

        }



//按钮事件

private void addANodeToolStripMenuItem_Click(object sender, EventArgs e)

        {

            Form2 form2 = new Form2();

            form2.ShowDialog();

        }







//form2

Form1 form1 = new Form1();



//按钮添加数据

private void button1_Click(object sender, EventArgs e)

        {

            string connstr = "Data Source=MICROSOF-602800\\SQLEXPRESS;Initial Catalog=tfc;Integrated Security=True";

            string commstr = "insert into tfctable(node,parent) values('"+textBox1.Text+"','--')";

            SqlConnection conn = new SqlConnection(connstr);

            SqlCommand comm = new SqlCommand(commstr, conn);

            conn.Open();

            comm.ExecuteNonQuery();

            conn.Close();

            form1.loadfromtfctable();      //好像是这里没什么用