Question

I have a check if a form is already open. If it’t not, it will open, if it is, it will activate the form + use a SwitchTab(int i) function. Here is some code:

public partial class Insert : Form {
    public Insert() {
        InitializeComponent();
    }

    public Insert(int tab) : this() {
        SwitchTab(tab);
    }

    public void SwitchTab(int tab) {
        tabControl1.SelectedIndex = tab;
    }
}

private void OpenInsert(int tab) {

        // Loop through all forms
        foreach (Form f in Application.OpenForms) {

            // Check if form of Insert type is found
            if (f.GetType() == typeof(Insert)) {
                f.Activate();

                // Unknown function
                f.SwitchTab(tab)

                return;
            }
        }

        // Not found, open form
        Insert insert = new Insert(tab);
        insert.Show();
    }

The reason behind this is that the Insert form has multiple tabs and I want to switch tab if an other button in the menu is clicked. The problem is that where I want to call the SwitchTab() function, the compiler doesnt know that it’s a Insert class, but it only passes when it is. So is there some way to forcefully let it know it’s a instance of insert?

Answer 1

You would have to tell that it is, like so:

((Insert)f).SwitchTab(tab)

This will try to cast the form to it, but will throw an Exception if its not. But since you check it, there shouldn’t be a problem 🙂