At times we want to delete all the items from a SharePoint List. Here are some excellent solutions to delete all the SharePoint list items efficiently.

Below is the PurgeList method from Keith Richie which does an excellent job of Purging items in a list. Here is a CodePlex tool and  one more solution to deal with the same problem.

/// <summary>
/// Purges items and folders from a list
/// Define WSSV3 to remove list folders
/// </summary>
/// The SPList you want to
/// purge items from
private static void PurgeList(SPList list)
{
Console.WriteLine("Purging list: " + list.Title);
Console.WriteLine("Base Type: " + list.BaseType.ToString());

// ===========================================================
// list.ItemCount returns a count that includes all items
// "AND" folders.
// You can't use list.Items.DeleteItemById() to remove a
// folder
// ===========================================================
System.Collections.Hashtable hItems =
new System.Collections.Hashtable(list.ItemCount);

// ===========================================================
// SPList.Items returns all list items in the entire list
// regardless of folder containment
// Note, just because list.ItemCount includes folders,
// list.Items does not.
// ===========================================================
foreach (SPListItem item in list.Items)
hItems.Add(item.ID,null);

// Remove the list items
foreach (int ID in hItems.Keys)
list.Items.DeleteItemById(ID);
// Clear the hashtable
hItems.Clear();
// ===========================================================
// SPList.Folders returns all folder items in the entire list
// regardless of parent folder containment
// ===========================================================
foreach (SPListItem item in list.Folders)
hItems.Add(item.ID,null);

// Remove the folder items
foreach (int ID in hItems.Keys)
{
list.Folders.DeleteItemById(ID);
}
}