Question: In my code, I want to remove the img tag which doesn't have src value.
 I am using **HTMLAgilitypack's HtmlDocument** object.
 I am finding the img which doesn't have src value and trying to remove it.. but it gives me error Collection was modified; enumeration operation may not execute.
 Can anyone help me for this?
 The code which I have used is:

```
foreach (HtmlNode node in doc.DocumentNode.DescendantNodes())
{
    if (node.Name.ToLower() == "img")
    {                            
           string src = node.Attributes["src"].Value;
           if (string.IsNullOrEmpty(src))
           {
               node.ParentNode.RemoveChild(node, false);    
           }
   }
   else
   {
             ..........// i am performing other operations on document
   }
}

```

Answer: 
It seems you're modifying the collection during the enumeration by using `HtmlNode.RemoveChild` method. 

To fix this you need is to copy your nodes to a separate list/array by calling e.g. [`Enumerable.ToList<T>()`](http://msdn.microsoft.com/en-us/library/bb342261.aspx) or [`Enumerable.ToArray<T>()`](http://msdn.microsoft.com/en-us/library/bb298736.aspx).

```
var nodesToRemove = doc.DocumentNode
    .SelectNodes("//img[not(string-length(normalize-space(@src)))]")
    .ToList();

foreach (var node in nodesToRemove)
    node.Remove();

```

If I'm right, the problem will disappear.
```
var emptyImages = doc.DocumentNode
 .Descendants("img")
 .Where(x => x.Attributes["src"] == null || x.Attributes["src"].Value == String.Empty)
 .Select(x => x.XPath)
 .ToList(); 

emptyImages.ForEach(xpath => { 
      var node = doc.DocumentNode.SelectSingleNode(xpath);
      if (node != null) { node.Remove(); }
    });

```