Closing of all Previous Forms and Opening of New Form in C#

C# Corner

Sourav Kumar Das

8y19.8kVisual Basic .NET

How to Close background Forms whenever a new form is opened in Windows Forms C#?

It should not be the specific form to be closed.....
It should close all the background forms whenever a form is opened....

If there's a solution or link please send me......

23 Replies

Know the answer? Post it — somebody with the same question will find it here.

Gaurav Gahlot8y ago
@ Sreekanth
form.Closed += (s, args) => this.Close();
This line of code binds an anonymous method with the Closed event of form. So, when the closed event will be raised or triggered, this method will handle that event.
+1
Sreekanth Reddy8y ago
I found the below solution in stack overflow :
https://stackoverflow.com/questions/9029351/close-all-open-forms-except-the-main-menu-in-c-sharp
List
openForms = new List();
foreach (Form f in Application.OpenForms)
openForms.Add(f);
foreach (Form f in openForms)
{
if (f.Name != "Menu")
f.Close();
}
Or you can use a for loop:
for (int i = Application.OpenForms.Count - 1; i >= 0; i--)
{
if (Application.OpenForms[i].Name != "Menu")
Application.OpenForms[i].Close();
}
+1
Sreekanth Reddy8y ago
@Rama Krishna
Can I know. What the below line refers to which you had stated ?
form.Closed += (s, args) => this.Close();
+1
Gaurav Gahlot8y ago
Hi Sourav!

You are getting an error, because you are modifying the collection that you are currently itterating on. So, this is surely not going to work.

Take a note of the following points:
closing Form1, which the main form in your case, will close the application
you should not close Form1, rather hide it
How to hide? As rightly pointed by @Rama, you should not itterate over the OpenForms because it is not efficient. So, you can do somethng like:
private void btnNewForm_Click(object sender, EventArgs e)
{
        // hide the current form, Form1
        this.Hide();

        var newForm = new Form2();
        newForm.Show();
}
This should solve, your errors. However, the solution might wary based on your usecase.

I hope this helps.

Thank you!
+1
Dorababu Meka8y ago
Try this code
List openForms = new List();

foreach (Form f in Application.OpenForms)
    openForms.Add(f);

foreach (Form f in openForms)
{
        f.Close();
}
Or
Form[] forms = Application.OpenForms.Cast().ToArray();
foreach (Form thisForm in forms)
{
    thisForm.Close();
}
+1
EMEKE JOSHUA8y ago
1. private void btnNewForm_Click(object sender, EventArgs e)
2. {
3. Form newForm = new Form();
5. this.Hide();
6. newForm.Show();
7. }
+1

Sourav Kumar Das8y ago

using MDI technique

If there's a solution please send me the link.....

Sourav Kumar Das8y ago

But we are only closing specific form at your given solution....

Because if it implements in MDI form in which it has multiple forms, so at that time how i can use it..

@Amit Gupta

Amit Gupta8y ago

@Sourav

If you want to hide your main form as well then you can use @Rama's solution. Your whole code will look like this

private void btnOpenForm_Click(object sender, EventArgs e)
{
Form form = new Form();
form.FormClosed += delegate
{
//this.Close();
// if you want to open the main form then comment the above line
// and uncomment the below line
this.Show();
form = null;
};
this.Hide();
form.Show();
form.Activate();
}

Change above code to suit your needs

Sourav Kumar Das8y ago

I accept your previous solution but the background form is not closing.

@Amit Gupta

Amit Gupta8y ago

Hey

As Application.OpenForms is readonly collection and cannot be modified using foreach iteration, use for loop instead. Your code will look like below

private void btnOpenForm_Click(object sender, EventArgs e)
{
CloseAllForm();
Form form = new Form();
form.Show();
}
void CloseAllForm()
{
for (int x = 0; x < Application.OpenForms.Count; x++)
{
if (Application.OpenForms[x] != this)
Application.OpenForms[x].Close();
}
}

Good Luck !!

Sourav Kumar Das8y ago

It's Showing same error...@Amit Gupta

Amit Gupta8y ago

load();
Form2 frm = new Form2();
frm.Show();
// Put your load body under try catch

Sourav Kumar Das8y ago

Can you ellaborate it...at which part I should place that load function.

@Amit Gupta

Amit Gupta8y ago

Hi Rama Loop will only execute when it has any opened form. However, to achieve a task there aee many ways. He can apply any of the solution.

Amit Gupta8y ago

Call that load method before opening a new form.

Sourav Kumar Das8y ago

But I should not specify that this form should be closed at background whenever i open a new form at foreground...@Rama Krishna

Sourav Kumar Das8y ago

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

Form2 frm = new Form2();

frm.Show();

load();

}

private void load()

{

foreach (Form f in Application.OpenForms)

f.Close();

}

Like this way.....

But it showing error...@Amit Gupta

Rama Krishna8y ago

Hi amit,

I think it's not better Idea because every time he has to loop and then hide Instead he could try what I provided

Amit Gupta8y ago

Create a function and write that code under that and whenever you are opening a form, just call that function.

Sourav Kumar Das8y ago

foreach (Form f in Application.OpenForms)

f Close();

at where I should apply this one..@Amit Gupta

Rama Krishna8y ago

Hi Sourav,

1. First hide your current form

this.Hide();

2. Second initialize your new form

NewForm form = new NewForm ();

3. Third use below line

form.Closed += (s, args) => this.Close();

4. Finally use below line

form.Show();

Entire code looks like below

this.Hide();

NewForm form = new NewForm();

form.Closed += (s, args) => this.Close();

form.Show();

Amit Gupta8y ago

Try this

foreach (Form f in Application.OpenForms)
f Close();

Closing of all Previous Forms and Opening of New Form in C#

@ Sreekanthform.Closed += (s, args) => this.Close();

@Amit Gupta

@ Sreekanth
form.Closed += (s, args) => this.Close();