如何避免重复的形式创作.​​NET Windows窗体？ [英] How to avoid duplicate form creation in .NET Windows Forms?

问题描述

我使用.NET Windows窗体。我的MDI父窗体包含菜单。如果点击菜单的形式将被显示。到现在为止没有任何问题。

I am using .NET Windows Forms. My MDI parent form contains the menu. If click the menu the form will be displayed. Up to now no problem.

UserForm uf = new UserForm();
uf.Show();
uf.MdiParent = this;

如果我再次点击创建窗体的另一个副本的菜单。如何解决这个问题呢？

If I click the menu again another duplicate of the form is created. How to solve this issue?

推荐答案

最彻底的方法是简单地跟踪形式实例的生命周期。订阅的FormClosed事件这样做。例如：

The cleanest way is to simply track the lifetime of the form instance. Do so by subscribing the FormClosed event. For example:

    private UserForm userFormInstance;

    private void showUserForm_Click(object sender, EventArgs e) {
        if (userFormInstance != null) {
            userFormInstance.WindowState = FormWindowState.Normal;
            userFormInstance.Focus();
        }
        else {
            userFormInstance = new UserForm();
            userFormInstance.MdiParent = this;
            userFormInstance.FormClosed += (o, ea) => userFormInstance = null;
            userFormInstance.Show();
        }
    }

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