Selecting multiple Listbox items through code

Question

Hi there I have searched for a while now and can't seem to find a solution to my problem, I have tried multiple methods to select multiple items in my listbox through code however none have worked, The best result I got was 1 selected item in my listbox.

Basically I want to select multiple items of the same value.

below is my code, sorry if I seem newbie but I am new to programming and still learning basic stuff.

 foreach (string p in listBox1.Items)
 {
           if (p == searchstring) 
           {
                 index = listBox1.Items.IndexOf(p);
                 listBox1.SetSelected(index,true);

           }
 }

So as you can see I am trying to tell the program to loop through all the items in my listbox, and for every item that equals "searchstring" get the index and set it as selected.

However all this code does is select the first item in the list that equals "searchstring" makes it selected and stops, it doesn't iterate through all the "searchstring" items.

Is SelectionMode on your list box set to Multiple?

shf301
– shf301

2012-10-29 22:52:09 +00:00
Commented Oct 29, 2012 at 22:52 — shf301
– shf301, Commented Oct 29, 2012 at 22:52

Nikola Davidovic · Accepted Answer · 2012-10-29 23:12:29Z

13

As suggested in the comment, you should set SelectionMode to either MulitSimple or MultiExpanded depending on your needs, but you also need to use for or while loop instead offoreach, because foreach loop doesn't allow the collection to be changed during iterations. Therefore, even setting this Property won't make your code run and you will get the exception. Try this:

for(int i = 0; i<listBox1.Items.Count;i++)
{
     string p = listBox1.Items[i].ToString();
     if (p == searchstring)
     {
          listBox1.SetSelected(i, true);

     }
}

You can set SelectionMode either in the Properties window when using designer or in, for instance, constructor of your Form using this code:

listBox1.SelectionMode = System.Windows.Forms.SelectionMode.MultiSimple;

edited Oct 29, 2012 at 23:12

answered Oct 29, 2012 at 23:05

Nikola Davidovic

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2 Comments

Lee O. Over a year ago

His foreach loop is fine. You just can't add or remove items from a collection you are iterating through. Which he is not doing.

Nikola Davidovic Over a year ago

@LeeO. Try it yourself, and you will see that it throws an exception. In most cases I check the code before posting (whenever I am able to create the testbed), I don't have enough reputation to allow myself to post code that's not working.

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