Extract the last element and add it to the end in list by changing a property value

Question

I have a list like this

CustomerSearch.cs

int id;
string searchedWord;

If for example, if this result is like this

[
 {id: 1, searchedWord :"test"}
 {id: 2, searchedWord: "news"}
]

I am trying to copy the last element in the list and append to the existing list and increment the id number value.

The expected result is

[
 {id: 1, searchedWord :"test"}
 {id: 2, searchedWord: "news"}
 {id: 3, searchedWord: "news"}
]

I could do this way

CustomerSearch customerSearch=new CustomerSearch();
customerSearch.Id=result.ElementAt(result.Count()-1).Id;
customerSearch.SearchedWord=result.ElementAt(result.Count()-1).SearchedWord;

List<CustomerSearch> newResult=new List<CustomerSearch>();
foreach(var mycustomerSearch in result)
{
 newResult.Add(mycustomerSearch);
}
newResult.Insert(1, customerSearch);
newResult.ElementAt(2).Id=3;

I don't think, this is the optimal way, if there is a better way to do this, please share it, thanks. We can create the expected result as a new list or with that existing list.

Answer 1

Assuming you may modify the original list result :

CustomerSearch customerSearch = new CustomerSearch {
  Id = result.Last().Id + 1,
  SearchedWord = result.Last().SearchedWord
};

result.Add(customerSearch);

• Use Linq Last() to access the last element of result .
• Use Object Initializers to initialize the new element nicely.

If you may not modify result :

CustomerSearch customerSearch = new CustomerSearch {
  Id = result.Last().Id + 1,
  SearchedWord = result.Last().SearchedWord
};

List<CustomerSearch> newResult = result.Select(x => x).ToList();

newResult.Add(customerSearch);

• Use Linq Select() followed by ToList() to clone the original list.

Note that Last() throws an exception if result is null or empty. To protect against this, the above operation should be preceded by a check for those cases:

if (results == null || !results.Any())
{
  // handle in some way, perhaps by returning.
}

• Use Linq Any() to check if result is empty.