Problem after listbox clear()

Question

Hi

 

I'm getting SelectedIndex value -1 after clearing a Listbox and repopulating it. Below is the code:

 

//..........
        public Process[] processes;
        private void Form1_Load(object sender, EventArgs e)
        {
            EnumProcs();
        }

        private void EnumProcs(){
            processes = Process.GetProcesses();

            foreach (Process process in processes)
            {
                //Get whatever attribute for process
                listBox_processes.Items.Add(process.ProcessName.ToString());
                listBox2.Items.Add(process.HandleCount.ToString());
            }
        }

        private void listBox_processes_SelectedIndexChanged(object sender, EventArgs e)
        {
            listBox_processes.Items.Clear();
            processes = null;
            EnumProcs();
            Process ProcessCurrent = processes[listBox_processes.SelectedIndex]; // ** I get -1 as SelectedIndex **
//.......

 Above, I use EnumProcs() to Enumerate system processes and load their names into a Listbox. After 1st population in Form1_Load(), I call EnumProcs() when ever the user selects an item from the Listbox with the proccess names. In SelectedIndexChanged(), I clear() the Listbox before calling EnumProcs(). But when I click an item in the Listbox, SelectedIndex returns -1, though Listbox item count shows 50+.

 

How to fix this?

 

Thanks.

Answer 1

When you clear and refill the listbox, the selection is lost. That's why the SelectedIndex becomes -1.

Answer 2

Sorry, I don't know if I'm misunderstanding the answer. But After I clear the Listbox, I fill it again calling EnumProc(), hence getting 50+ items in it when debugging. So how could SelectedIndex be -1 when the Listbox is filled?

Answer 3

Because you are clearing the list box before using "listBox_processes.SelectedIndex" you are getting -1.

 

You should  do "Process ProcessCurrent = processes[listBox_processes.SelectedIndex];" before "listBox_processes.Item.Clear();" so that you can get the selected item properly.