winform 选择文件窗体模块

这是当textBox7文本框中无内容时，才可以运行的，且还关联了一个button3，如不需要，都可以删除
if (string.IsNullOrEmpty(textBox7.Text))
                {
                    //此时弹出一个可以选择文件的窗体
                    OpenFileDialog fileDialog = new OpenFileDialog();
                    //一次只能选取一个文件
                    fileDialog.Multiselect = false;
                    fileDialog.Title = "请选择文件";
                    fileDialog.Filter = "所有文件(*.*)|*.*";
                    if (fileDialog.ShowDialog() == DialogResult.OK)
                    {
                        textBox7.Text = fileDialog.FileName;
                        textBox7.Enabled = false;
                        button3.Text = "重新输入";
                    }
                }
                else
                {
                    textBox7.Enabled = false;
                    button3.Text = "重新输入";
                    ////此时弹出一个可以选择文件的窗体
                    //OpenFileDialog fileDialog = new OpenFileDialog();
                    ////一次只能选取一个文件
                    //fileDialog.Multiselect = false;
                    //fileDialog.Title = "请选择文件";
                    //fileDialog.Filter = "所有文件(*.*)|*.*";
                    //if (fileDialog.ShowDialog() == DialogResult.OK)
                    //{
                    //    textBox7.Text = fileDialog.FileName;
                    //    textBox7.Enabled = false;
                    //    button3.Text = "重新输入";
                    //}
                }
            }
            else if (button3.Text == "重新输入")
            {
                textBox7.Enabled = true;
                button3.Text = "确认输入";
            }