Clear items from listbox2 to listbox1

Question

1.00/5 (2 votes)

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Hello,

I want to know how to clear items from listbox2 which will then erase items from listbox1 as well. Similar items, that is.

What I have tried:

C#

if (listBox2.Items == listBox1.Items)
            {
                listBox1.Items.Clear();

            }

This code is totally wrong, but I want to fix it.

Posted 27-Jan-22 5:53am

Ashkan X

Updated 28-Jan-22 8:35am

Sean Ewington

v2

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Comments

Richard MacCutchan 27-Jan-22 12:33pm

You need to create a loop through listbox2 and as you delete each item you need to see if it is also in listbox1.

2 solutions

Solution 2

Try something like this.

C#

var listBox1 = new ListBox();
var listBox2 = new ListBox();
for (int i = 0; i < listBox1.Items.Count; i++)
{
    int index = listBox2.Items.IndexOf(listBox1.Items[i]);
    if (index != -1)
    {
        listBox2.Items.RemoveAt(index);
    }
}

You can't use foreach with list boxes, so use for.

IndexOf finds the item in the second list box. Items start at 0, and -1 means the item was not found. You could also instead use Items.Contains to see if the item is in the second list box.

Posted 27-Jan-22 7:05am

RobertSF

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M Imran Ansari · Accepted Answer · 2022-01-27T06:54:00

You can't change two dependent ListBox through loop on runtime because an enumerator is associated with List on traversing and It can only be used if the list does not change. You can achieve this with third container. First you have you find out matched items and then remove from lists. Like below code:

List<object> toRemove = new List<object>();
foreach (string item1 in listBox1.Items)
{
     foreach (string item2 in listBox2.Items)
     {
             if (item1.Contains(item2))
             {
                    toRemove.Add(item2);                        
                    break;
             }
     }
}
if (toRemove.Count > 0)
{
     foreach (var item in toRemove)
     {
            listBox1.Items.Remove(item);
            listBox2.Items.Remove(item);
     }
}