Question

Possible Duplicate:
Remove duplicates from a List<T> in C#

i have a List like below (so big email list):
source list :

item 0 : [e-mail]|32432  
item 1 : [e-mail]|32432|test23  
item 2 : [e-mail]|32432|test65  
item 3 : [e-mail]|32432|test32 

the important part of each item is email address and the other parts(separated with pipes are not important) but i want to keep them in final list.
as i said my list is to big and i think it’s not recommended to use another list.

how can i remove duplicate emails (entire item) form that list without using LINQ ?
my codes are like below :

private void WorkOnFile(UploadedFile file, string filePath)
{
    File.SetAttributes(filePath, FileAttributes.Archive);

    FileSecurity fSecurity = File.GetAccessControl(filePath);
    fSecurity.AddAccessRule(new FileSystemAccessRule(@"Everyone",
                                                    FileSystemRights.FullControl,
                                                    AccessControlType.Allow));
    File.SetAccessControl(filePath, fSecurity);

    string[] lines = File.ReadAllLines(filePath);
    List<string> list_lines = new List<string>(lines);
    var new_lines = list_lines.Select(line => string.Join("|", line.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries)));
    List<string> new_list_lines = new List<string>(new_lines);
    int Duplicate_Count = 0;
    RemoveDuplicates(ref new_list_lines, ref Duplicate_Count);
    File.WriteAllLines(filePath, new_list_lines.ToArray());
}

private void RemoveDuplicates(ref List<string> list_lines, ref int Duplicate_Count)
{
    char[] splitter = { '|' };
    list_lines.ForEach(delegate(string line)
    {
        // ??
    });
}

EDIT :
some duplicate email addrresses in that list have different parts ->
what can i do about them :
mean

[e-mail]|32432|test23   
and   
[e-mail]|asdsa|324234

Thanks in advance.

Answer 1

private void RemoveDuplicates(ref List<string> list_lines, ref int Duplicate_Count)
{
    Duplicate_Count = 0;
    List<string> list_lines2 = new List<string>();
    HashSet<string> hash = new HashSet<string>();

    foreach (string line in list_lines)
    {
        string[] split = line.Split('|');
        string firstPart = split.Length > 0 ? split[0] : string.Empty;

        if (hash.Add(firstPart)) 
        {
            list_lines2.Add(line);
        }
        else
        {
            Duplicate_Count++;
        }
    }

    list_lines = list_lines2;
}