If the DialogResult for this property is set to anything other than None, and if the parent form was displayed through the ShowDialog method, clicking the button closes the parent form without your having to hook up any events. The form's DialogResult property is then set to the DialogResult of the button when the button is clicked.

For example, to create a "Yes/No/Cancel" dialog box, simply add three buttons and set their DialogResult properties to Yes, No, and Cancel.

如果button click里需要做额外的操作或者检查，比如不满足某条件就不关闭父窗口，可以设置DialogResult 为none。

private void buttonOk_Click(object sender, EventArgs e)

 {

            if (this.comboBox1.SelectedItem == null)

            {

                MessageBox.Show("Please select the target project!", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);

                this.DialogResult = DialogResult.None;

            }

 }

2. Form.AcceptButton, CancelButton Property设置子为子Button, 用户按下Enter， Esc键会触发相应的Button。相当于为Button设置Enter， Esc快捷键。