What is the purpose of IEnumerator

Hi all i searched for IEnumerator but could not get to understand it.it would be great help if anyone helps me.

basically trying to understand the its role in this code

string requestUriString = URL;
if (requestUriString.IndexOf("http://", StringComparison.InvariantCultureIgnoreCase) < 0)
{
    requestUriString = "http://" + requestUriString;
}
WebRequest request = WebRequest.Create(requestUriString);
try
{
    IEnumerator enumerator;
    StreamReader reader = new StreamReader(request.GetResponse().GetResponseStream(), Encoding.UTF8);
    string sSourceString = reader.ReadToEnd();
    reader.Close();
    string str6 = this.funcParseStringFromString2String(sSourceString, "<div class=\"title\">", "<div class=\"searches_related\">", false);
    ArrayList list = new ArrayList();
    list = this.funcParseStringFromString2Stringx(str6, "<h3><a ", "</h3>", false);
    int num = this.DataGridView2.RowCount + 1;
    try
    {
        enumerator = list.GetEnumerator();
        while (enumerator.MoveNe开发者_开发问答xt())
        {
            string str8 = Conversions.ToString(enumerator.Current);
            string str7 = this.funcParseStringFromString2String(str8, "title=\"", "\" href=", false);
            string str5 = this.funcParseStringFromString2String(str8, "\" href=\"", "\">", false).Replace("\" class=\"rated", "");
            this.DataGridView2.Rows.Add(new string[] { Conversions.ToString(num), Conversions.ToString(false), str7, str5 });
            this.lblInsProg.Text = "Done: " + Conversions.ToString(this.DataGridView2.Rows.Count) + " Articles found";
            num++;
        }
    }
    finally
    {
        if (enumerator is IDisposable)
        {
            (enumerator as IDisposable).Dispose();
        }
    }
    if (list.Count == 0)
    {
        this.lblInsProg.Text = "No results found for " + this.search.Text + "!";
        this.Button11.Enabled = false;
    }
    else
    {
        this.Button11.Enabled = true;
    }
    if (this.DataGridView2.RowCount != 0)
    {
        this.Button15.Visible = true;
    }
    return Conversions.ToString(0);
}
catch (WebException exception1)
{
    ProjectData.SetProjectError(exception1);
    WebException exception = exception1;
    ProjectData.ClearProjectError();
}
return Conversions.ToString(0);

---

This part of the code:

try
{
    enumerator = list.GetEnumerator();
    while (enumerator.MoveNext())
    {
        string str8 = Conversions.ToString(enumerator.Current);
        //...
    }
}
finally
{
    if (enumerator is IDisposable)
    {
        (enumerator as IDisposable).Dispose();
    }
}

is basically the same as:

foreach(var value in list)
{
    string str8 = Conversions.ToString(value);
    //...
}

but the latter is far more readable, don't you think ?

---

IEnumerator allows you to iterate over a list, array, etc. (anything that implements IEnumerable) and process each element one-by-one.

If you're familiar with a foreach loop in C#, IEnumerator is what it uses under the covers. For example, this:

List<string> myList = new List<string>() { "one", "two", "three" };

foreach(string elem in myList)
{
    Console.WriteLine(elem);
}

Is actually translated to something like this:

List<string> myList = new List<string>() { "one", "two", "three" };

IEnumerator<string> enumerator = list.GetEnumerator();

while(enumerator.MoveNext())
{
    string elem = enumerator.Current;

    Console.WriteLine(elem);
}

(This is simplified, as there are other cleanup operations that foreach does, like disposing the enumerator if it implements IDisposable, but this addresses the relevant portion)

In fact, your entire try-finally code block is almost a dead-on copy of how the foreach construct gets translated into IL.

---

The IEnumerator interface allows the while() {} part of the code to loop through list one by one with the MoveNext() method.

It is the C# "iterator"-pattern implementation. Any class that implemented the interface IEnumerator can be iterated over. Often it is used with the foreach syntactic sugar.

It's a somewhat sloppy way of writing it. The try/finally is not really necessary. I would expect that section of the code to look like this:

var list = new ArrayList(); // (or a newer, generic container, like List<T>)
...
foreach (var item in list)
{
    string str8 = Conversions.ToString(item);
    ...
}

---

It's an Iterator. As far as I know it follow the Iterator pattern

---

I would read Jon Skeet's book C# in depth, it is the best explanation of this I have seen although the version of the book I am referring to is 3 and the version that is out now is 4 - I don't know if it is covered the same in that version...

This is not as in-depth as the book but this is useful... http://www.yoda.arachsys.com/csharp/csharp2/iterators.html