My List.Add in C# keeps adding and rewriting all previous items

Question

foreach (var item in tweets)
{
     XmlNode user = users[i];
     XmlNode text = texts[i];
     XmlNode id = ids[i];
     string userstr = user.InnerText;
     string textstr = text.InnerText;
     string idstr = id.InnerText;
     tweet.user = userstr;
     tweet.text = textstr;
     tweet.id = idstr;
     tweetlist.Add(tweet);
     ++i;

 }

 return tweetlist;

i put a break by the tweetlist.add(tweet) line so i'm sure that it is getting the correct data but everytime it adds a new item to the list it replaces the first one and adds a new one for example

List{id = 1, name = "bob"} + {id = 2, name = "jenny"}

becomes

list {id = 2 name = "jenny"}, {id = 2 , name = "jenny"}

What are you doing with return value? If its only returning one, is there a chance its overwriting part of the original list? — BugFinder, Aug 10 '15 at 16:25
You're just changing the same `tweet` and adding it to the list again. Create a new object. — Charles Mager, Aug 10 '15 at 16:25
you need to understand the use of the key word `new` in regards to creating a new object.. — MethodMan, Aug 10 '15 at 16:26

score 0 · Accepted Answer · answered Aug 10 '15 at 16:25

You are modifying a tweet object and then adding it to the list, but you never switch to a different tweet instance before modifying it again in the next loop, so essentially you are adding the same instance to the list again and again (remember: you add object references, not copies!) and just modify that single instance every time.

score 0 · Answer 2 · answered Aug 10 '15 at 16:25

0

In the first example you are repeatedly adding a single instance of 'tweet' and then modifying that instance, so all entries in the list will be the same. You need to create a new instance of tweet each time.

answered Aug 10 '15 at 16:25

PaulF

6,673
2
18
29

My List.Add in C# keeps adding and rewriting all previous items

2 Answers2