Question

To avoid the error “Collection was modified after the enumerator was instantiated”
I found a number of recommendations to use the following lines before looping through the Request.ServerVariables.Keys collection:

IEnumerator en = Request.ServerVariables.Keys.GetEnumerator();
en.MoveNext();

Looking at the MSDN example, they set the Server Variables to a collection, then iterate through that collection without calling GetEnumerator or MoveNext.

Two questions:

1. Why do we need to call GetEnumerator and MoveNext?
2. Which is the better approach if using ASP.NET and C# 4.0?

Answer 1

You can also use:

 string[] keys = Request.ServerVariables.AllKeys;
 foreach(string key in keys )
 {
      if(Request.ServerVariables[key] != null)
      {
           string value = Request.ServerVariables[key];
      }
 }