How can I find the last element in a List

Question

The following is an extract from my code  public class AllIntegerIDs        public AllIntegerIDs                              m MessageID   0          m MessageType   0          m ClassID   0          m CategoryID   0          m MessageText   null                  AllIntegerIDs                    public void SetIntegerValues  int messageID  int messagetype          int classID  int categoryID                this m MessageID   messageID          this m MessageType   messagetype          this m ClassID   classID          this m CategoryID   categoryID                 public string m MessageText      public int m MessageID      public int m MessageType      public int m ClassID      public int m CategoryID     I am trying to use the following in my main   function code  List lt AllIntegerIDs gt  integerList   new List lt AllIntegerIDs gt         some code here that is ised for following assignments        integerList Add new AllIntegerIDs        index       integerList index  m MessageID    int IntegerIDsSubstring IntOffset      integerList index  m MessageType    int IntegerIDsSubstring IntOffset   1      integerList index  m ClassID    int IntegerIDsSubstring IntOffset   2      integerList index  m CategoryID    int IntegerIDsSubstring IntOffset   3      integerList index  m MessageText   MessageTextSubstring     Problem is here  I am trying to print all elements in my List using a for loop  for  int cnt3   0   cnt3  lt   integerList FindLastIndex   cnt3       lt ----PROBLEM HERE      Console WriteLine  quot  0  t 1  t 2  t 3  t 4  n quot   integerList cnt3  m MessageID integerList cnt3  m MessageType integerList cnt3  m ClassID integerList cnt3  m CategoryID  integerList cnt3  m MessageText      I want to find the last element so that I equate cnt3 in my for loop and print out all entries in the List  Each element in the list is an object of the class AllIntegerIDs as mentioned above in the code sample  How do I find the last valid entry in the List  Should I use something like integerList Find integerList   m MessageText    null   If I use that it will need an index that will range from 0 to whatever maximum  Means I will have to use another for loop which I do not intend to use  Is there a shorter better way

User · Answer

Though this was posted 11 years ago  I m sure the right number of answers is one more than there are  You can also doing something like   if  integerList Count  gt  0      var item   integerList  1     See the tutorial post on the MS C  docs here from a few months back  I would personally still stick with LastOrDefault     Last   but thought I d share this  EDIT  Just realised another answer has mentioned this with another doc link

User · Answer

Use the Count property  The last index will be Count - 1   for  int cnt3   0   cnt3  lt  integerList Count  cnt3

User · Answer

Lets get at the root of the question  how to address the last element of a List safely     Assuming  List lt string gt  myList   new List lt string gt       Then    NOT safe on an empty list  string myString   myList myList Count -1      equivalent to the above line when Count is 0  bad index string otherString   myList -1      count-1  is a bad habit unless you first guarantee the list is not empty   There is not a convenient way around checking for the empty list except to do it   The shortest way I can think of is  string myString    myList Count    0    myList   myList Count-1           you could go all out and make a delegate that always returns true  and pass it to FindLast  which will return the last value  or default constructed valye if the list is empty   This function starts at the end of the list so will be Big O 1  or constant time  despite the method normally being O n      somewhere in your codebase  a strange delegate is defined private static bool alwaysTrue string in        return true       Wherever you are working with the list string myString   myList FindLast alwaysTrue     The FindLast method is ugly if you count the delegate part  but it only needs to be declared one place  If the list is empty  it will return a default constructed value of the list type    for string  Taking the alwaysTrue delegate a step further  making it a template instead of string type  would be more useful

User · Answer

int lastInt   integerList integerList Count-1

User · Answer

Change  for  int cnt3   0   cnt3  lt   integerList FindLastIndex   cnt3      to  for  int cnt3   0   cnt3  lt  integerList Count  cnt3

User · Answer

Why not just use the Count property on the List   for int cnt3   0  cnt3  lt  integerList Count  cnt3

User · Answer

Independent of your original question  you will get better performance if you capture references to local variables rather than index into your list multiple times   AllIntegerIDs ids   new AllIntegerIDs    ids m MessageID    int IntegerIDsSubstring IntOffset   ids m MessageType    int IntegerIDsSubstring IntOffset   1   ids m ClassID    int IntegerIDsSubstring IntOffset   2   ids m CategoryID    int IntegerIDsSubstring IntOffset   3   ids m MessageText   MessageTextSubstring  integerList Add ids     And in your for loop   for  int cnt3   0   cnt3  lt  integerList Count   cnt3       lt ----PROBLEM HERE      AllIntegerIDs ids   integerList cnt3      Console WriteLine   0  t 1  t 2  t 3  t 4  n         ids m MessageID ids m MessageType ids m ClassID ids m CategoryID  ids m MessageText

User · Answer

To get the last item of a collection use LastOrDefault   and Last   extension methods  var lastItem   integerList LastOrDefault      OR  var lastItem   integerList Last      Remeber to add using System Linq   or this method won t be available

User · Answer

If you just want to access the last item in the list you can do if integerList Count gt 0       var item   integerList integerList Count - 1      to get the total number of items in the list you can use the Count property var itemCount   integerList Count

User · Answer

I would have to agree a foreach would be a lot easier something like  foreach AllIntegerIDs allIntegerIDs in integerList    Console WriteLine   0  t 1  t 2  t 3  t 4  n   allIntegerIDs m MessageID  allIntegerIDs m MessageType  allIntegerIDs m ClassID  allIntegerIDs m CategoryID  allIntegerIDs m MessageText       Also I would suggest you add properties to access your information instead of public fields  depending on your  net version you can add it like public int MessageType  get  set   and get rid of the m  from your public fields  properties etc as it shouldnt be there

User · Answer

In C  8 0 you can get the last item with   operator full explanation  List lt char gt  list        var value   list  1        Gets translated to  var value   list list Count - 1

[c#] How can I find the last element in a List<>?

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