If list contain duplicate value then get total count - C#

Question

Hello Everyone,

 

I have list items.

 

 

This 3 records contain images, that is image path from database. I want to get total size of the image group by ArchievedName .

 

1st item,

 

 

 

2nd item,

 

 

 

3rd item,

 

 

 

I have tried, 

List<Tble_Documents> objDocumentUserSetup = new List<Tble_Documents>();

bjDocumentUserSetup = objUserSetUp1.AsEnumerable().Select(m => new Tble_Documents()
                  {
                      ArchievedName = m.ArchievedName,
                      UpdatedDate = m.UpdatedDate,
                      Fullname = m.Fullname,
                      FilePath = m.FilePath + m.Parent_File_Name + "_" + m.Child_File_Name,
                      docCount = m.docCount,
                      FileSize = FormatBytes(new System.IO.FileInfo(m.FilePath + m.Parent_File_Name + "_" + m.Child_File_Name).Length) /*How can do here?*/
                  }).ToList();

private static string FormatBytes(long bytes)
       {
           string[] Suffix = { "B", "KB", "MB", "GB", "TB" };
           int i;
           double dblSByte = bytes;
           for (i = 0; i < Suffix.Length && bytes >= 1024; i++, bytes /= 1024)
           {
               dblSByte = bytes / 1024.0;
           }

           return String.Format("{0:0.##} {1}", dblSByte, Suffix[i]);
       }

 Please help me.