C#: Check if Form is already running

While implementing WinForms programming you might come across a situation where you do not want to open a form multiple times on an event.  A common practice in the event handler function is:

From1 firstForm = new From1();
firstForm.Show(); 

This will open your form, fine! But what if the event happens again and the previously opened firstForm has not been closed yet? A new firstForm will be opened and this will go on.  To check if a form is already running you’ll have to look for it in the Application.OpenForms collection. When a form is opened it is added to that collection. Here’s a boolean method that checks whether a form is open or not. This code snippet shows you how to check if is your MDI container has a specific MDI child open or not. The sample below looks though each of the mdi children in the container for a instance of the form you want to open. If an instance is found, the form is brought to the front. If an instance of the form is not found, the code opens a new instance of the form.

Boolean Method

To check whether the form is already opened or not      

      private bool CheckForm(Form form)

        {

            form = Application.OpenForms[form.Text];

            if (form != null)

                return true;

            else

                return false;

        }

Example use:

                       Form2 formSecond = new Form2();

                        if (!CheckForm(formSecond ))

                        {

                            formSecond .Show();

                        }

                        else

                        {

                            formSecond .WindowState = FormWindowState.Normal;

                            formSecond .BringToFront();

                            formSecond .Activate();

                        }