How to ignore overselect in listbox

Question

Currently I have 6 listbox. Im trying to select all 5 other listbox items in the same row as the one manually selected.

However, Im getting an error :

An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll

Cannot evaluate expression because the current thread is in a stack overflow state.

Below is an example of code for one of the listbox, repeated for all other listbox.

private void listBox1_SelectedIndexChanged(object sender, EventArgs e) {

      listBox1.SelectedIndexChanged=1;
        listBox3.SelectedIndex = -1;
        listBox2.SelectedIndex = -1;
        listBox4.SelectedIndex = -1;
        listBox5.SelectedIndex = -1;
        listBox6.SelectedIndex = -1;
        listBox2.ClearSelected();
       listBox3.ClearSelected();
       listBox4.ClearSelected();
       listBox5.ClearSelected();
       listBox6.ClearSelected();
       int  a = listBox1.SelectedIndex;
       int b = listBox2.SelectedIndex;
       int c = listBox3.SelectedIndex;
       int d = listBox4.SelectedIndex;
       int f = listBox5.SelectedIndex;
       int g = listBox6.SelectedIndex;


        if (a >-1)
        {
           // listBox1.SetSelected(a,true);
            listBox2.SetSelected(a, true);
            listBox3.SetSelected(a, true);
            listBox4.SetSelected(a, true);
            listBox5.SetSelected(a, true);
            listBox6.SetSelected(a, true);
        }
        else if (b > -1)
        {
            listBox1.SetSelected(b, true);
           // listBox2.SetSelected(b, true);
            listBox3.SetSelected(b, true);
            listBox4.SetSelected(b, true);
            listBox5.SetSelected(b, true);
            listBox6.SetSelected(b, true);
        }
        else if (c > -1)
        {
            listBox1.SetSelected(c, true);
            listBox2.SetSelected(c, true);
         //   listBox3.SetSelected(c, true);
            listBox4.SetSelected(c, true);
            listBox5.SetSelected(c, true);
            listBox6.SetSelected(c, true);
        }
        else if (d > -1)
        {
            listBox1.SetSelected(d, true);
            listBox2.SetSelected(d, true);
            listBox3.SetSelected(d, true);
          //  listBox4.SetSelected(d, true);
            listBox5.SetSelected(d, true);
            listBox6.SetSelected(d, true);
        }
        else if (f > -1)
        {
            listBox1.SetSelected(f, true);
            listBox2.SetSelected(f, true);
            listBox3.SetSelected(f, true);
            listBox4.SetSelected(f, true);
           // listBox5.SetSelected(f, true);
            listBox6.SetSelected(f, true);
        }
        else if (g > -1)
        {
            listBox1.SetSelected(g, true);
            listBox2.SetSelected(g, true);
            listBox3.SetSelected(g, true);
            listBox4.SetSelected(g, true);
            listBox5.SetSelected(g, true);
           // listBox6.SetSelected(g, true);
        }


    }


    private void listBox2_SelectedIndexChanged(object sender, EventArgs e)
    {
        listBox1.SelectedIndex = -1;
        listBox3.SelectedIndex = -1;
        listBox4.SelectedIndex = -1;
        listBox5.SelectedIndex = -1;
        listBox6.SelectedIndex = -1;
        listBox1.ClearSelected();
        listBox3.ClearSelected();
        listBox4.ClearSelected();
        listBox5.ClearSelected();
        listBox6.ClearSelected();
        int a = listBox1.SelectedIndex;
        int b = listBox2.SelectedIndex;
        int c = listBox3.SelectedIndex;
        int d = listBox4.SelectedIndex;
        int f = listBox5.SelectedIndex;
        int g = listBox6.SelectedIndex;


        if (a > -1)
        {
            // listBox1.SetSelected(a,true);
            listBox2.SetSelected(a, true);
            listBox3.SetSelected(a, true);
            listBox4.SetSelected(a, true);
            listBox5.SetSelected(a, true);
            listBox6.SetSelected(a, true);
        }
        else if (b > -1)
        {
            listBox1.SetSelected(b, true);
            // listBox2.SetSelected(b, true);
            listBox3.SetSelected(b, true);
            listBox4.SetSelected(b, true);
            listBox5.SetSelected(b, true);
            listBox6.SetSelected(b, true);
        }
        else if (c > -1)
        {
            listBox1.SetSelected(c, true);
            listBox2.SetSelected(c, true);
            //   listBox3.SetSelected(c, true);
            listBox4.SetSelected(c, true);
            listBox5.SetSelected(c, true);
            listBox6.SetSelected(c, true);
        }
        else if (d > -1)
        {
            listBox1.SetSelected(d, true);
            listBox2.SetSelected(d, true);
            listBox3.SetSelected(d, true);
            //  listBox4.SetSelected(d, true);
            listBox5.SetSelected(d, true);
            listBox6.SetSelected(d, true);
        }
        else if (f > -1)
        {
            listBox1.SetSelected(f, true);
            listBox2.SetSelected(f, true);
            listBox3.SetSelected(f, true);
            listBox4.SetSelected(f, true);
            // listBox5.SetSelected(f, true);
            listBox6.SetSelected(f, true);
        }
        else if (g > -1)
        {
            listBox1.SetSelected(g, true);
            listBox2.SetSelected(g, true);
            listBox3.SetSelected(g, true);
            listBox4.SetSelected(g, true);
            listBox5.SetSelected(g, true);
            // listBox6.SetSelected(g, true);
        }

}

Never use an empty Try-Catch. Is a + 1 > 0 another way of saying a > -1? — LarsTech
– LarsTech, Commented Mar 11, 2016 at 18:10
do you have only listBox2 fires SelectedIndexChanged event which handled in listBox2_SelectedIndexChanged? — skalinkin
– skalinkin, Commented Mar 11, 2016 at 18:11
@skalinkin Sorry Im not strong in english, but if i get what you meant, the answer is yes. Please take a look at my full code via the answer section. Thanks — Adrian
– Adrian, Commented Mar 11, 2016 at 21:55

LarsTech · Accepted Answer · 2016-03-11 18:18:08Z

0

Your code is probably changing the index within the SelectedIndexChanged event somewhere in your code.

Try using a flag instead:

listBox1.SelectedIndexChanged += listBox_SelectedIndexChanged;
listBox2.SelectedIndexChanged += listBox_SelectedIndexChanged;
listBox3.SelectedIndexChanged += listBox_SelectedIndexChanged;

bool changingSelection = false;

void listBox_SelectedIndexChanged(object sender, EventArgs e) {
  if (!changingSelection) {
    int index = ((ListBox)sender).SelectedIndex;
    if (index > -1) {
      changingSelection = true;
      listBox1.SetSelected(index, true);
      listBox2.SetSelected(index, true);
      listBox3.SetSelected(index, true);
      changingSelection = false;
    }
  }
}

answered Mar 11, 2016 at 18:18

LarsTech

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10 Comments

Adrian Over a year ago

Hi. Apologies, Im new to programming so Im still trying to figure out what is going on in your code. Thanks for your help.

LarsTech Over a year ago

@Adrian Feel free to ask me anything you don't understand about my example.

Adrian Over a year ago

Sure. listBox1.SelectedIndexChanged += listBox_SelectedIndexChanged; listBox2.SelectedIndexChanged += listBox_SelectedIndexChanged; listBox3.SelectedIndexChanged += listBox_SelectedIndexChanged; whats does this do ?

Adrian Over a year ago

is flag the same as FlagsAttribute ? What does it mean/do?

LarsTech Over a year ago

The flag is just referring to a boolean variable: changingSelection. When its true, it ignores the code inside the if block, because when you change the selection of a ListBox, it will always fire this code. The listBox1.SelectedindexChange += stuff is assigning the event to the method. This is a manual way of wiring up the events instead of using the designer. I assign each of the ListBoxes to use the same method. Usually you only assign the event once, preferably in the form's constructor.

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