how can i implement this foreach loop with for loop? because i heard that for loop is much faster than foreach loop.
foreach (RV item in gridview.SelectedItems.ToList())
{
R req= db.Requests.Single(x => x.Id == item.Id);
...
}
You heard incorrectly.
for loops are not much faster than foreach loops.
In fact, for some collections, foreach loops are much faster than for loops.
ToList() is slower than either of them.
If you really want to make your code faster, you should use an O(n) LINQ join instead of the O(n2) Single() call.
foreach loop faster then for loop?
IList<T>.for (int i = 0; i < gridview.SelectedItems.Count(); i++)
{
R req = db.Requests.Single(x => x.ID == (gridview.SelectedItems(i) as RV).Id);
...
}
Although I doubt there will be any noticeable performance gain.
Count()s.There is no point in converting your selected items to a list, if you are enumerating them with foreach anyway. Also a for loop requires you to call ToList, which internally uses a foreach!
I do not know, if your o/r-mapper can cope with Contains. If it does try this:
var items = db.Requests.Where(x => gridview.SelectedItems.Contains(x.Id));
This will reduce the number of database requests. This is where time gets lost, not in the foreach!
forloop; I don't see your question.