Introduction
Its a normal question from the Winform Developers of the intial stage "How can I restrict my child form from opening twice" or "How can I make a form not to open if its already opened" lets see how it works
Background
I had a WindowsForm Application with more than 100 Forms and More than 50 MenustripItems. The user opens the form using the click event of the MenustripButtons. Now the issue is the user may open a form for eg FORM1 and a later they may leave it opened or minimized and had accidently or knowingly pressed the Same MenustripButton again .since we are using the Form.Show() function to display a form ,one more instance of form will be created and displayed.So I decided to stop it by restricting the user opening a form again when its already open .
Using the code
I first created a function IsAlreadyOpen() which get the WindowsForm as input parameter
The Below function will loop through the all opened formns in the application and check whether the input parameter form is same ass that of any opened form and will return true if the form is already opened and will return false if the form is not opened
private bool IsAlreadyOpen(Type formType)
{
bool isOpen = false;
foreach (Form f in Application.OpenForms)
{
if (f.GetType() == formType)
{
f.BringToFront();
f.WindowState = FormWindowState.Normal;
isOpen = true;
}
}
return isOpen;
}
And in the click event of the ToolstripMenuItem I created an instance of required form and then I send the form to the function IsAlreadyOpen() and if it return false I intialized the instance and showed it
private void companyToolStripMenuItem1_Click(object sender, EventArgs e)
{
Master.CompanyMasterForm cmpnymasterform = null;
bool isFormOpen = IsAlreadyOpen(typeof(Master.CompanyMasterForm));
if (isFormOpen == false)
{
cmpnymasterform = new Master.CompanyMasterForm();
cmpnymasterform.StartPosition = FormStartPosition.CenterScreen;
cmpnymasterform.MdiParent = this;
cmpnymasterform.Show();
}
}
Forget to say ..I had used Winforms with C#.net ..and as always Winform Rockzz
Points of Interest
It should have been more simpler if I had created a function for this click event functions also and pass only formname to that function .which itself call IsAlreadyOpen()
History
Keep a running update of any changes or improvements you've made here.
