Thread: Problem after listbox clear()

  1. #1
    Android geek@02's Avatar
    Join Date
    Mar 2004
    Kurunegala Colony, Sri Lanka, Sri Lanka

    Problem after listbox clear()


    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?

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  2. #2
    Registered User
    Join Date
    Jun 2017
    The problem is when
    listBox_processes_SelectedIndexChanged is called you delete all items and SelectedIndex becomes -1.
    When you fill the listbox again SelectedIndex is still -1.

    Why do you delete it and fill it again? Do you think the processes have changed?

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