c# - 如何检查表单是否打开，如果打开关闭表单？

Question

如何检查表单是否打开，以及是否打开以关闭表单？

我尝试了以下方法，测试了一些代码，但它一直说表单没有打开，即使我知道它是：

 foreach(Form a in Application.OpenForms) 
 {
     if (a is YouLikeHits_Settings) 
     {
         // About form is open
         MessageBox.Show("form open");
         break;
     }
     // About form is not open...
     MessageBox.Show("form not open");
     break;
 }

Answer 1

Application.OpenForms包含打开的表单。如果表单在此集合中，则将其打开。否则它不会打开（可能是关闭的）。

if (Application.OpenForms.OfType<YouLikeHits_Settings>().Any())
    MessageBox.Show("Form is opened");
else
    MessageBox.Show("Form is not opened");

Answer 2

这肯定会奏效

            if (Application.OpenForms.OfType<frm_YouLikeHits_Settings>().Any())
            {
                Application.OpenForms.OfType<frm_YouLikeHits_Settings>().First().Close();
            }
            frm_YouLikeHits_Settings f1= new frm_YouLikeHits_Settings();
            f1.MdiParent = this;
            f1.Show();

Answer 3

try
{
    if (Application.OpenForms.OfType<talkForm>().Any())
    {
        talkForm frm = new talkForm();
        frm.Close();
        MessageBox.Show("Form is opened");
    }
    else
    {
        talkForm frm = new talkForm();
        frm.Show();
        MessageBox.Show("Form is not opened");
    }
}
catch(Exception ex)
{

}