这样三个函数能重构成一个函数吗？

Question

winform的，先判断父窗口下有无同类型的子窗体，有则激活之，无则新建之
        public static void newPForm(Form thisForm)
        {
            Form newForm = null;
            foreach (Form f in thisForm.MdiParent.MdiChildren)
            {
                if (f is frmP)//关键是这里， frmP是一个class名，class名不能直接当作参数传递
                {
                    newForm = f;
                    break;
                }            }
            if (newForm == null)
            {
                newForm = new frmP();
                newForm.MdiParent = thisForm.MdiParent;
                newForm.Show();
            }
            else
            {
                newForm.Activate();
            }
        }
        public static void newIForm(Form thisForm)
        {
            Form newForm = null;
            foreach (Form f in thisForm.MdiParent.MdiChildren)
            {
                if (f is frmIRegister)
                {
                    newForm = f;
                    break;
                }            }
            if (newForm == null)
            {
                newForm = new frmIRegister();
                newForm.MdiParent = thisForm.MdiParent;
                newForm.Show();
            }
            else
            {
                newForm.Activate();
            }
        }
        public static void newCForm(Form thisForm)
        {
            Form newForm = null;
            foreach (Form f in thisForm.MdiParent.MdiChildren)
            {
                if (f is frmC)
                {
                    newForm = f;
                    break;
                }            }
            if (newForm == null)
            {
                newForm = new frmC();
                newForm.MdiParent = thisForm.MdiParent;
                newForm.Show();
            }
            else
            {
                newForm.Activate();
            }
        }

Answer 1

那就把这3个写在一起啊，   
if (f is frmC)
      {
          newForm = f;
          break;
          if (newForm == null)
            {
                newForm = new frmC();
                newForm.MdiParent = thisForm.MdiParent;
                newForm.Show();
            }       }
else if（f is frmB）
{
          newForm = f;
          break;}

Answer 2

select case 也可以实现。

Answer 3

public void New(Form f, Form f2)
        {
            Type t = typeof(t2);
            if (f is t) { }
        }

Answer 4

//最后查找资料后结果是这样的，可能代码有些冗余
#region 查找并打开子窗体函数
        /// <summary>
        /// 根据子窗体的名称类型打开子窗体
        /// </summary>
        /// <param name="childTypeString">子窗体名称类型</param>
        public static void findAndOpenWindow(Form thisForm, string childTypeString)
        {
            Form myChild = null;
            if (!containMDIChild(thisForm,childTypeString))
            {
                try
                {
                    Assembly assembly = Assembly.GetExecutingAssembly();
                    // Create data type using type string
                    Type typForm = assembly.GetType(childTypeString);                    // Create object using type's "InvokeMember" method
                    Object obj = typForm.InvokeMember(
                        null,
                        BindingFlags.DeclaredOnly |
                        BindingFlags.Public | BindingFlags.NonPublic |
                        BindingFlags.Instance | BindingFlags.CreateInstance,
                        null,
                        null,
                        null);                    // Show child form 
                    if (obj != null)
                    {
                        myChild = obj as Form;
                        myChild.MdiParent = thisForm.MdiParent;
                        myChild.WindowState = FormWindowState.Maximized;
                        myChild.Show();
                        myChild.Focus();
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message.ToString());
                    //MessageBox.Show("未能加载程序模块", "警告！");
                }
            }
        }
        /// <summary>
        /// 根据子窗体的名称类型查找子窗体
        /// </summary>
        /// <param name="ChildTypeString">子窗体的名称类型</param>
        /// <returns></returns>
        private static bool containMDIChild(Form thisForm, string childTypeString)
        {
            Form myMDIChild = null;
            foreach (Form f in thisForm.MdiParent.MdiChildren)
            {
                string a = f.GetType().ToString();
                if (f.GetType().ToString() == childTypeString)
                {
                    myMDIChild = f;
                    break;
                }
            }            // 显示已经存在的窗体
            if (myMDIChild != null)
            {
                /*
                myMDIChild.TopMost = true;
                myMDIChild.WindowState = FormWindowState.Maximized;                myMDIChild.Show();
                myMDIChild.Focus();
                 */
                myMDIChild.Activate();
                return true;
            }
            else
            {
                return false;
            }
        }
        #endregion