Question

Suppose that I have the following code snippet:

var data=new List<string>(){"One","Two","Three"};
for(int i=0 ; i<data.Count ; i++){
  if(data[i]=="One"){
    data.RemoveAt(i);
  }
}

The following code throws exception.

My question is what is the best way to avoid this exception and to remove the element while looping?

Answer 1

If you need to remove elements then you must iterate backwards so you can remove elements from the end of the list:

var data=new List<string>(){"One","Two","Three"};
for(int i=data.Count - 1; i > -1; i--)
{
    if(data[i]=="One")
    {
        data.RemoveAt(i);
    }
}

However, there are more efficient ways to do this with LINQ (as indicated by the other answers).