以下代码实现 B窗体调用A窗体的方法。

其实就是传 this

窗体A：

public partial class FormA : Form

    {

        public FormA()

        {

            InitializeComponent();

        }

        public void AAA()

        {

            MessageBox.Show("来自A窗体的方法");

        }

        private void button1_Click(object sender, EventArgs e)

        {

            FormB bFrm = new FormB(this);

            bFrm.Show();

        }

    }

窗体B：

 public partial class FormB : Form

    {

        FormA aFrm;

        public FormB(FormA frm)

        {

            InitializeComponent();

            this.aFrm = frm;

        }

        private void button1_Click(object sender, EventArgs e)

        {

            this.aFrm.AAA();

        }

    }