调用静态方法以关闭表格

Question

I have two Windows Forms - Form1 and Form2 . I need to close Form1 from a button click event in Form2 . How do I do it if the method in Form1 is static ?

Form1

namespace WinClose
{
    public partial class Form1 : Form
    {     
        public static void CloseForm()
        {
            this.Close();
        }       
    }
}

Form2

namespace WinClose
{
    public partial class Form2 : Form
    {       
        private void button1_Click(object sender, EventArgs e)
        {
            Form1.CloseForm();            
        }
    }
}

I am getting the below error

Keyword "this" is not valid in static property, static method or static field initializer.

I have heard of Single-ton , Multi-ton concepts. Is there a need to convert the class or is there any easy way to handle this?

EDIT

There can be multiple instances of Form1 and Form2 . Consider the below situation.

• User opens Form1 , then opens Form2 from Form1 , in button click of Form2 , Form1 should be closed (INSTANCE 1)
• User can again open another instance of Form1 , then opens Form2 from Form1 , in button click of Form2 , Form1 should be closed. (INSTANCE 2)

ie, When the user clicks button in Form2 (INSTANCE 2) , only one Form1 (INSTANCE 2) should be closed.

Any help would be appreciated.
Thanks in advance.

Answer 1

If you want to close only the Form1 that opened Form2 , you must pass Form1 as a parameter to Form2's constructor:

namespace WinClose
{
    public partial class Form2 : Form
    {
        Form1 form1;

        public Form2(Form1 form1) {
            InitializeComponent();
            this.form1 = form1;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.form1.Close();            
        }
    }
}

If you want to close all instances of Form1:

namespace WinClose
{
    public partial class Form2 : Form
    {       
        private void button1_Click(object sender, EventArgs e)
        {
            foreach (var form in Application.OpenForms.OfType<Form1>().ToList())
                form.Close ();
        }
    }
}

Answer 2

You obviously can't have a this reference in a static method. Which instance would it be referring to?

You can make it a singleton, but this sounds like a design smell.

I see no reason the method should be static. If Form2 needs to know about Form1 , then it should have a reference to a Form1 instance.

Alternatively, if Form2 should not know about Form1 , but Form1 knows about Form2 , then Form2 can fire an event which signals Form1 to close.

Answer 3

Overthinking, close it directly. An instance of a form cannot be closed by a static method, since the class (static methods are part of the class) doesn't know about the instance.

namespace WinClose
{
    public partial class Form2 : Form
    {       
        Form1 form1;
        private void button1_Click(object sender, EventArgs e)
        {
            this.form1.Close();             
        }
    }
}

Value form1 can be set via the constructor or via a property from the caller.

Answer 4

You are calling in wrong way

check following

namespace WinClose
{
    public partial class Form1 : Form
    {     
        //no need of CloseForm
    }
}


namespace WinClose
{
    public partial class Form2 : Form
    {       
        private void button1_Click(object sender, EventArgs e)
        {
            //Form1 o = new Form();//instance needed
            Form1 o= Application.OpenForms.OfType<Form1>        
            if(o != null)
            {    
              o.Close();       
            }     
        }
    }
}