如何通过函数调用mdi表单

Question

如何创建一个跟随代码的函数，以便我可以不必编写以下整个代码来使表单用作MDICHILD表单。

Students stu = null;
    private void studentsToolStripMenuItem1_Click(object sender, EventArgs e)
    {
        if (stu == null || stu.IsDisposed)
        {
            stu = new Students();
            stu.MdiParent = this;
            stu.Show();
        }
        else
        {
            stu.Activate();
        }
    }

虽然我想要这样

private void studentsToolStripMenuItem1_Click(object sender, EventArgs e)
    {
        CreateMdiChild(Students);
    }

和功能应该是这样的

public void CreateMdiChild(Form form)
    {
        //expected code            
    }

Answer 1

您可以使方法通用，例如：

public void CreateMdiChildOrActivate<T>(ref T instance) where T : Form, new()
{
    if (instance == null || instance.IsDisposed)
    {
        instance = new T();
        instance.MdiParent = this;
        instance.Show();
    }
    else
    {
        instance.Activate();
    }
}

用法：

private void studentsToolStripMenuItem1_Click(object sender, EventArgs e)
{
    CreateMdiChildOrActivate(ref this.stu);
}

编辑：

如果您不想为每个表单创建一个类字段，您可以这样做：

创建一个包含每个表单类型的打开表单的类字典字段：

private Dictionary<Type,Form> openForms = new Dictionary<Type,Form>();

然后将以前的方法更改为：

public void CreateMdiChildOrActivate<T>() where T : Form, new()
{
    Form instance;
    openForms.TryGetValue(typeof(T), out instance);
    if (instance == null || instance.IsDisposed)
    {
        instance = new T();
        openForms[typeof(T)] = instance;
        instance.MdiParent = this;
        instance.Show();
    }
    else
    {
        instance.Activate();
    }
}

现在你可以像这样调用它：

private void studentsToolStripMenuItem1_Click(object sender, EventArgs e)
{
    CreateMdiChildOrActivate<Student>();
}

Answer 2

public void CreateMdiChild<T>(Form f) where T : Form, new()
{
    foreach (Form frm in f.MdiChildren)
    {
        if (frm.GetType() == typeof(T))
        {                        
            if (frm.WindowState == FormWindowState.Minimized)
            {
                frm.WindowState = FormWindowState.Normal;
            }
            else
            {
                frm.Activate();
            }
            return;
        }                    
    }
    T t = new T();
    t.MdiParent = f;
    t.Show();
}

用法

CreateMdiChild<MyForm>()