Tip 91: Determining If a Form Is Loaded

May 22, 1995

Abstract

A Visual Basic® application may contain many different forms. This article presents a function that can be used to determine if a form is currently loaded into memory.

Is the Form Loaded in Memory?

Because a Visual Basic® application can contain several forms, you need to be able to determine if a form is actually loaded into memory. The function presented in the example program below tests to see if a form is loaded. This function will not load the form—it simply tests to see if it is already in memory.

Example Program

This program shows how to find out if a specific form is already loaded in a running Visual Basic application.

1. Create a new project in Visual Basic. Form1 is created by default.
   
   
2. From the Insert menu, select Form. Form2 is created by default.
   
   
3. From the Insert menu, select Form. Form3 is created by default.
   
   
4. Add the following code to the Form_Load event for Form1:

   Private Sub Form_Load()
   Form2.Show
   End Sub
   

5. Add a Command Button control to Form1. Command1 is created by default.
   
   
6. Add the following code to the Click event for Command1:

   Private Sub Command1_Click()
   Dim X As Integer
   X = IsFormLoaded(Form2)
   If X Then
   MsgBox "Form2 is loaded"
   End If
   X = IsFormLoaded(Form3)
   If X = False Then
   MsgBox "Form3 is not loaded"
   End If
   End Sub
   

7. Create a new function called IsFormLoaded. Add the following code to this function:

   Function IsFormLoaded(FormToCheck As Form) As Integer
       Dim Y As Integer
       
       For Y = 0 To Forms.Count - 1
           If Forms(Y) Is FormToCheck Then
               IsFormLoaded = True
               Exit Function
           End If
       Next
       IsFormLoaded = False
   End Function
   

When you run this program, click the Command Button. A message box will pop up on the screen displaying the "Form2 is loaded" message. Click the OK command button. A second message box is immediately shown displaying the "Form3 is not loaded" message.