Deleting Document Library Items for large list size Failed?

For novice to use this code, specify the strings variables siteURL, listName.
The maximum items that your program can delete is 25000 which can be changed.

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using (SPSite site = new SPSite(siteURL))
{
 using (SPWeb web = site.OpenWeb())
                {
                    web.AllowUnsafeUpdates = true;
                    StringBuilder sbDelete = new StringBuilder();
                    SPList spList = web.GetList("/" + listName);
                    sbDelete.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>");
                    string command = "<Method><SetList Scope=\"Request\">" + spList.ID +
                        "</SetList><SetVar Name=\"ID\">{0}</SetVar><SetVar Name=\"Cmd\">Delete</SetVar><SetVar Name=\"owsfileref\">{1}</SetVar></Method>";
                    int limit = 0;
                    foreach (SPListItem item in spList.Items)
                    {
                        limit++;
                        if (limit > 25000)
                            break;
                        sbDelete.Append(string.Format(command, item.ID.ToString(), item.File.Url));
                    }
                    sbDelete.Append("</Batch>");

                    web.ProcessBatchData(sbDelete.ToString());
                    web.Update();
                    web.AllowUnsafeUpdates = false;
                }
}