Styjun

I'm trying to make a listbox where i can add items to it using datagridview, the thing is i want to determine which item is duplicate and how many times it duplicate.

• item1


• item1


• item2


• item2


• item2

output item1=2, item2=3

Here is the one that i tried which shows the last item that have been duplicate

int count = 0;

 for (int i = 0; i < listBox1.Items.Count; i++)
 
 var s = listBox1.Items[i].ToString();
 if (s.StartsWith(listfood))
 
 if (s == listfood)
 
 ++count;
 
 
 
MessageBox.Show(count.ToString());

Try

var duplicateItems = listBox1.Items.GroupBy(x => x.ToString())
 .Where(x => x.Count() > 1)
 .Select(x => new Value = x.Key, Count = x.Count() )
 .ToList();

using System.Linq;

// ...

var duplicates = listBox1.Items.GroupBy(x => x)
 .Where(g => g.Count() > 1)
 .Select(y => new ItemName = y.Key, Occurrences = y.Count() )
 .ToList();

foreach (var duplicate in duplicates)
 MessageBox.Show($"duplicate.ItemName: duplicate.Occurrences");

This solution uses LINQ to query the listBox1's Items collection and filter out any data we don't care about.

First, we use GroupBy to sort the items. Then, Where will filter out any items in the collection that only exist once. Select allows us to "project" the items remaining in the filtered collection into a "new form" (we use an anonymous type with an ItemName and Occurrences property to track the names of the duplicates and the number of times it appears in the collection).

Finally, ToList converts the collection from an IEnumerable<string> to aListtype.ToListis optional depending on how you plan on usingduplicates. In fact, my example doesn't need to callToListbecause aforeachloop can iterate over anIEnumerable` collection.

I know the Answers above will definitely work, but i can't understand it and make it work. This one works for me, where i transfer values of listbox to an array and check the duplicates inside that array.

 var list = new List<string>();
 foreach(var item in listBox1.Items)
 
 list.Add(item.ToString());
 
 var r = from b in list
 group b by b into g
 let count = g.Count()
 orderby count descending
 select new Value = g.Key, Count = count ;
 foreach(var x in q)
 
 MessageBox.Show("value: " + b.Value + " Count:" + b.Count);
 

Found my answer here