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Groupby and add items to a list

Posted on 2008-10-18
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Last Modified: 2013-12-17
Hello,

I am writing a C# program and in that I have a List<category> which I have defined. I am doing a group by on the items. My question is, how do I put these elements into the same List or even a different List? Do I need to use IEnumerator? If yes, then how do I do so?

Any help is greatly appreciated!

Thanks
Arjit
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Question by:arjitbhandari
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4 Comments
 
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Expert Comment

by:jandromeda
ID: 22750201
Your question is little bit unclear to me, but if you are trying to add items to certain places of the current list then you can use either List<T>).Insert(<index>,<T>) method or the List<T>.AddRange(<inderx>,IEnumerable<T>).
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Accepted Solution

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jandromeda earned 500 total points
ID: 22750225
Here is an example.
List<string> names = new List<string>();
			
			names.Add("John");
			names.Add("Jimmy");
			names.Add("Jason");
			names.Add("Jack");
			
			foreach (string name in names)
			{
				Console.WriteLine(name);
			}
			
			Console.WriteLine();
			
			// Add a name between Jimmy and Jason
			names.Insert(2, "Jaleem");
			
			foreach (string name in names)
			{
				Console.WriteLine(name);
			}
			
			List<string> moreNames = new List<string>();
			
			moreNames.Add("Mary-Anne");
			moreNames.Add("Samantha");
			
			// Add a collection of names between Jason and Jack
			names.InsertRange(4, moreNames);
			
			Console.WriteLine();
			
			foreach (string name in names)
			{
				Console.WriteLine(name);
			}

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Author Comment

by:arjitbhandari
ID: 22750446
Thanks for your reply.

Basically, I have defined 2 List, ret and ret1, with reference to the following code snippet. When I add elements to ret, I do not have any problem, but when I try to add elements to ret1, which is of same type, I get the following error:

 "Cannot initialize type with a collection initializer because it does not implement 'System.Collections.IEnumerable'"

Note that the purpose of this code is to "group by" elements in List ret. Do you have any suggestions for this?

Thanks
Arjit
ret.Add(new Category()
                            {
                                GivenName = contact.GivenName,
                                //   Surname = contact.Surname,
                                //   PhoneNumber = (string)contact.PhoneNumbers[0].Value,
                                CompanyName = contact.CompanyName,
                                JobTitle = contact.JobTitle,
                                BAddress = contact.PhysicalAddresses[0].Street,
                                City = contact.PhysicalAddresses[0].City,
                                State = contact.PhysicalAddresses[0].State,
                                Zip = contact.PhysicalAddresses[0].PostalCode,
                                Country = contact.PhysicalAddresses[0].CountryOrRegion
                                
                            });
                        var temp = from p in ret
                                   group p by p.Country
                                   ;
 
                        foreach (var i in temp)
                            foreach (var temp2 in i)
                            {
                                ret1.Add(new Category() { temp2.GivenName });
                            }

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Author Comment

by:arjitbhandari
ID: 22750671
I am also attaching the cs file for reference. Thanks in advance.

Arjit
collection.txt
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