Deleting multiple values from the list

Question

I have defined one list as

List<List<int>> thirdLevelIntersection = new List<List<int>>();

I wrote the code as

for(int i = 0; i < 57; i++)
{
    if(my condition)
        thirdLevelIntersection[i] = null;
    else
    {
       //some logic
    }    
}

so i get the list for 0 to 56 values and some arbitrary values are null like thirdlevelIntersection[1],thirdlevelIntersection[10],thirdlevelIntersection[21],thirdlevelIntersection[21],thirdlevelIntersection[14],thirdlevelIntersection[15],thirdlevelIntersection[51](total 7).

Now i want to remove this values from the list.

And have a list from thirdlevelIntersection[0] thirdlevelIntersection[49].

What should I do?

Answer 1

完成循环后，请尝试

thirdLevelIntersection.RemoveAll(list => list == null);

Answer 2

If you're creating thirdLevelIntersection from a sourceCollection of some type you can use Linq.

List<List<int>> thirdLevelIntersection = 
    (from item in sourceCollection
     where !(my condition)
     select item)
    .ToList();

Or if you're building up the list over multiple statements you can do it as you are creating it:

thirdLevelIntersection.AddRange(
    from item in sourceCollection
    where !(my condition)
    select item);

This eliminates the necessity to remove items from a list once they've been added.

Answer 3

You can do this while you're iterating over the list by calling RemoveAt() and then decrementing i (so the next value is considered).

List<List<int>> thirdLevelIntersection = new List<List<int>>();

for(int i=0;i<57;i++)
{
    if (my condition)
    {
        thirdLevelIntersection.RemoveAt(i--);
        continue;
    }
    else
    {
        //some logic
    }
}