Is there any way to do this, assign a value within a List.ForEach() statement?

Question

I have this:

var lineArray = line.Split(\';\');

lineArray.ToList().ForEach(x =>
{
    if (x == \"(null)\")
        x = \"NULL\";
    else
        x = string.         


        

Answer 1

you can construct a new list from your original one :

var newList = lineArray.Select(x => x == "(null)" ? "NULL" : string.Format("'{0}'", x));

Answer 2

don't use ForEach like that - use a for loop.

for (int i = 0; i < lineArray.Length; i++)
{
    if (lineArray[i] == "(null)")
        lineArray[i] = "NULL";
    else
        lineArray[i] = string.Format("'{0}'", lineArray[i]);
}

Answer 3

I think this small change will work

 var lineArray = line.Split(';').ToList();

        lineArray.ForEach(x =>
        {
            if (x == "(null)")
                x = "NULL";
            else
                x = string.Format("'{0}'", x);
        });

Below is a working example

string line = "a;b;null;c;";

var lineArray = line.Split(';').ToList();

    lineArray.ForEach(x =>
    {
        if (x == "(null)")
            x = "NULL";
        else
            x = string.Format("'{0}'", x);
    });

Result:

If you need just to remove (null) values from the list, you do not need to loop just use removeAll

    lineArray.RemoveAll(a=>a.Equals("(null)"));

working example below

Answer 4

var lineArray = line.Split(';')
                    .Select(x=>x == "(null)"
                               ? "NULL"
                               : string.Format("'{0}'", x))
                    .ToArray();

you are trying to use List<T>.ForEach(Action<T> action) with lambda expression (T is string here)

if lambda expression is replaced with named method it turns out that only method argument is modified, but changes are not reflected on calling side, because x is not ref argument

private void Replace(string x)
{
    if (x == "(null)")
        x = "NULL";
    else
        x = string.Format("'{0}'", x);
}

var list = lineArray.ToList();
list.ForEach(Replace);
// check list here and make sure that there are no changes

ForEach could work if T is a reference type and action modifies some properties but not the reference itself