Is there a way to use LINQ to modify a List in place?

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If I want to do the following:

C#

List<string> listOfStrings = new List<string>();

listOfStrings.Add("13");
listOfStrings.Add("14");
listOfStrings.Add("FooBar");
listOfStrings.Add("Dummy14Item");
listOfStrings.Add("Brontosaurus165LT");

//... add items here ...

// iterate through the list and find all items
// ending with "LT" and remove the last two characters
// from those items, but leave the list intact
for (int i = 0; i < listOfStrings.Count; i++)
{
    if (listOfStrings[i].EndsWith("LT"))
        listOfStrings[i] = listOfStrings[i].Replace("LT", "");
}

// list should now be
//
// 13
// 14
// FooBar
// Dummy14Item
// Brontosaurus165
//
// can I make this change with LINQ?

So is there a way to make a projection of the List<t> that contains essentially the same items except for the modification? I tried

C#

listOfStrings.ForEach(x => { if (x.EndsWith("LT")) x = x.Replace("LT", ""); });

But, unless I am doing something incorrectly, it doesn't seem to be working. One reason may be because the ForEach function takes as its parameter an Action<T> delegate, which passes T obj by value, not by reference.

Does anyone have a hint? I just hate the first block with the for(int i;i < list.Count; i++ ), it seems so gradeschool.

Brian

Posted 12-Sep-11 8:07am

Brian C Hart86.6K

Updated 12-Sep-11 8:13am

v2

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Herman<T>.Instance 12-Sep-11 15:35pm

in stead of the for loop you could have used foreach (string value in listOfString) {if value.EndsWith("LT") ......

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Herman<T>.Instance · Answer 1 · 2011-09-12T09:45:00

Solution 1

C#

int i = 0;

listOfStrings.ForEach(x =>
{
       if (x.EndsWith("LT")) 
       {
            listOfStrings[i] = x.Replace("LT", string.Empty);
       }
   i++;
}
);

Posted 12-Sep-11 9:45am

Herman<T>.Instance

Comments

Brian C Hart 12-Sep-11 16:45pm

I would also do

list = list.ConvertAll<string>(x => x.EndsWith("LT") ? x.Replace("LT", "") : x);

however this is another process of O(n) complexity that replaces my list with a whole new list, identical to the old except for the changed items. digimanus's answer is close; i just was hoping that i wouldn't have to declare an int i outside the ForEach call. It's almost as gradeschool as the OP.