Question

I would like to remove the duplicate elements from a List. Some elements of the list looks like this:

Book  23
Book  22
Book  19
Notebook 22
Notebook 19
Pen 23
Pen 22
Pen 19

To get rid of duplicate elements i’ve done this:

List<String> nodup = dup.Distinct().ToList();

I would like to keep in the list just

Book 23
Notebook 22
Pen 23

How can i do that ?

Answer 1

You can use LINQ in combination with some String operations to group all your itemy by name and MAX(Number):

var q = from str in list
        let Parts = str.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
        let item = Parts[ 0 ]
        let num = int.Parse(Parts[ 1 ])
        group new  { Name = item, Number = num } by item into Grp
        select new {
            Name  = Grp.Key,
            Value = Grp.Max(i => i.Number).ToString()
        };

var highestGroups = q.Select(g => 
    String.Format("{0} {1}", g.Name, g.Value)).ToList();

(Same as Reed’s approach but in query syntax which is better readable to my mind)

Edit: I cannot reproduce your comment that it does not work, here is sample data:

List<String> list = new List<String>();
list.Add("Book  23");
list.Add("Book  22");
list.Add("Book 19");
list.Add("Notebook  23");
list.Add("Notebook  22");
list.Add("Notebook  19");
list.Add("Pen  23");
list.Add("Pen  22");
list.Add("Pen  19");
list.Add("sheet 3");

var q = from str in list
        let Parts = str.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
        let item = Parts[ 0 ]
        let num = int.Parse(Parts[ 1 ])
        group new  { Name = item, Number = num } by item into Grp
        select new {
            Name  = Grp.Key,
            Value = Grp.Max(i => i.Number).ToString()
        };

var highestGroups = q.Select(g => String.Format("{0} {1}", g.Name, g.Value));
MessageBox.Show(String.Join(Environment.NewLine, highestGroups));

The result:

Book 23
Notebook 23
Pen 23
sheet 3