I have a loop inside my program, which loops through thousands of object to find the right one with particular id.
is there any better and faster way than this
int id;
SPList list = SPContext.Current.Web.Lists.TryGetList("DataLibrary");
IEnumerable<SPListItem> _dataitems = list.Items.OfType<SPListItem>();
foreach (SPListItem item in _dataextantitems)
{
if (item.ID == id)
{
title= item.Title;
}
}
Use the GetItemById of SPList.
var title = SPContext.Current.Web.Lists["DataLibrary"].GetItemById(id).Title;
If your list has a lot of columns, and you want to avoid pulling them all down, you can pull down just the Title column instead:
var title = SPContext.Current.Web.Lists["DataLibrary"]
.GetItemByIdSelectedFields(id, "Title").Title;
Now if you really want to use LINQ here you could use LINQ to Sharepoint, but it's not actually going to simplify the code a ton. After using SPMetal.exe to generate a file based on your lists, you'd be able to write:
using(var context = new YourContextNameHere(SPContext.Current.Site.Url))
{
var title = context.DataLibrary
.Where(item => item.ID == id)
.Select(item => item.Title)//to avoid pulling down other columns
.First();
}
Make sure your list is sorted. Then you can use the BinarySearch method of the list or write your own implementation. If not you can shorten your code using linq.
var itemToLookup = list.Items.OfType<SPListItem>().FirstOrDefault(x => x.ID == id);
if (itemToLookup != null)
{
//...
}
Related
I am trying to sort all the updated item in DataTableA, by coloring the item that has not been completely updated, and removing the item that has been updated completely from the DataTable. both The item that has been updated completely and the incomplete updated item are in "managed" table in the database, the discharge date will be null if it has not been completely updated.
Below code works but it can take all day for the page to run. This is C# webform.
The code below is writing on my code behind file:
foreach (GridDataItem dataItem in RadGrid1.Items)
{
var panu = dataItem["Inumber"];
var panum = panu.Text;
var _cas = db.managed.Any(b =>
b.panumber == panum && b.dischargedate != null);
var casm = db.managed.Any(b =>
b.panumber == panum && b.dischargedate == null);
if (_cas == true)
{
dataItem.Visible = false;
}
if (casm == true)
{
dataItem.BackColor = Color.Yellow;
}
}
As mentioned in the comment, each call to db.managed.Any will create a new SQL query.
There are various improvements you can make to speed this up:
First, you don't need to call db.managed.Any twice inside the loop, if it's checking the same unique entity. Call it just once and check dischargedate. This alone with speed up the loop 2x.
// one database call, fetching one column
var dischargedate = db.managed
.Select(x => x.dischargedate)
.FirstOrDefault(b => b.panumber == panum);
var _cas = dischargedate != null;
var casm = dischargedate == null;
If panumber is not a unique primary key and you don't have a sql index for this column, then each db.managed.Any call will scan all items in the table on each call. This can be easily solved by creating an index with panum and dischargedate, so if you don't have this index, create it.
Ideally, if the table is not huge, you can just load it all at once. But even if you have tens of millions of records, you can split the loop into several chunks, instead of repeating the same query over and over again.
Consider using better naming for your variables. _cas and casm are a poor choice of variable names.
Pro tip: Always code as if the person who ends up maintaining your code is a violent psychopath who knows where you live.
So if you don't have hundreds of thousands of items, here is the simplest fix: load panumber and discharge values for all rows from that table into memory, and then use a dictionary to instantly find the items:
// load all into memory
var allDischargeDates = await db.managed
.Select(x => new { x.panumber, x.dischargedate })
.ToListAsync(cancellationToken);
// create a dictionary so that you can quickly map panumber -> dischargedate
var dischargeDateByNumber = dbItems
.ToDictionary(x => x.panumber, x => x.dischargedate);
foreach (var dataItem in RadGrid1.Items)
{
var panu = dataItem["Inumber"];
var panum = panu.Text;
// this is very fast to check now
if (!dischargeDateByNumber.TryGetValue(panum, out DateTime? dischargeDate))
{
// no such entry - in this case your original code will just skip the item
return;
}
if (dischargeDate != null)
{
dataItem.Visible = false;
}
else
{
dataItem.BackColor = Color.Yellow;
}
}
If the table is huge and you only want to load certain items, you would do:
// get the list of numbers to fetch from the database
// (this should not be a large list!)
var someList = RadGrid1
.Items
.Select(x => x["Inumber"].Text)
.ToList();
// load these items into memory
var allDischargeDates = await db.managed
.Where(x => someList.Contains(x.panumber))
.Select(x => new { x.panumber, x.dischargedate })
.ToListAsync(cancellationToken);
But there is a limit on how large someList can be (you don't want to run this query for a list of 200 thousand items).
Well, 900 items might be worth simply fetching to a list in memory and then process that. It will definitely be faster, although it consumes more memory.
You can do something like this (assuming the type of managed is Managed):
List<Managed> myList = db.managed.ToList();
That will fetch the whole table.
Now replace your code with:
foreach (GridDataItem dataItem in RadGrid1.Items)
{
var panu = dataItem["Inumber"];
var panum = panu.Text;
var _cas = myList .Any(b =>
b.panumber == panum && b.dischargedate != null);
var casm = myList .Any(b =>
b.panumber == panum && b.dischargedate == null);
if (_cas == true)
{
dataItem.Visible = false;
}
if (casm == true)
{
dataItem.BackColor = Color.Yellow;
}
}
You should see a huge performance approvement.
Another thing: You don't mention what database you're using, but you should make sure the panumber column is properly indexed.
I have a object called Items. I use that object like so.
List<List<Items>> myItems = new List<List<Items>>();
I want to know how to get a specific List<Items> out of the List<List<Items>> object. Currently I am using foreach loops with some rules to find a specific List<Items>
This is currently what I am doing
foreach (List<Items> db2Items in db2Data)
{
foreach (List<Items> apiItems in apiData)
{
if (db2Items[0].Value == apiItems[0].Value && db2Items[27].Value == apiItems[27].Value)
{
/// Some other logic here
}
}
}
I was wanting to use LINQ to get the matching List<items> out of apiData and if I have a result then do the logic I wanted to do.
Not really sure what you're trying to accomplish, but if you want to get a list in a list based on a certain condition you can do it like this:
var item = db2Data.Where(x => x.Where(y => y.[value] == [YourCondition]).Any()).FirstOrDefault();
the "x.Where(y => y == [YourCondition]).Any()" will return true if the condition is met, and firstordefault will then return the list that meets the condition.
I have figured it out.
Using LINQ:
foreach (List<Items> db2Items in db2Data)
{
IEnumerable<List<Items>> theItem = from item in apiData
where item[0].Value == db2Items[0].Value && item[27]>Value == db2Items[27].Value
select item;
if (theItem.ToList().Count > 0)
{
// Do something
}
}
So I have a search-input and checkboxes that passes the values to the controller when there are inputs. And I want to use these values to get something back from the database. The search-input is a string and it works and intended. Here is the code for the search-input:
public async Task<ViewResult> Index(string searchString, List<int> checkedTypes)
{
var products = from p in _db.Products select p;
ViewData["CurrentFilter"] = searchString;
if (!string.IsNullOrEmpty(searchString))
{
products = products.Where(p => p.Name.ToLower().Contains(searchString));
}
return View(products);
}
However the checkboxes values are stored in a list. So basically I want to do the same as the code above, but with a list. So basically an idea is like this:
if(checkedTypes != null)
{
foreach (var i in checkedTypes)
{
products = products.Where(p => p.TypeId == i));
}
}
If I do it like the code above, I just get the last (i) from the loop. Another solution I did was this:
if(checkedTypes != null)
{
var temp = new List<Product>();
foreach (var i in checkedTypes)
{
temp.AddRange(products.Where(p => p.TypeId == i));
}
products = temp.AsQueryable();
}
But when I did it like that I get this error:
InvalidOperationException: The provider for the source IQueryable doesn't implement IAsyncQueryProvider. Only providers that implement IAsyncQueryProvider can be used for Entity Framework asynchronous operations.
So anyone have a solution that I can use? Or is there a better way to handle checkboxes in the controller?
Assuming you are using EF Core (also the same is true for linq2db) - it supports translating filtering with local collection, i.e. Where(x => checkedTypes.Contains(x.SomeId)).
If you have "and" logic to filter by searchString and checkedTypes than you can conditionally add Where clause:
if (!string.IsNullOrEmpty(searchString))
{
products = products.Where(p => p.Name.ToLower().Contains(searchString));
}
if(checkedTypes != null)
{
products = products.Where(p => checkedTypes.Contains(p.TypeId));
}
P.S.
Also you should be able to change your first line to:
var products = _db.Products.AsQueryable();
I have a DB used for a production line. It has an Orders table, and Ordertracker table, an Item table, and an Itemtracker table.
Both Orders and Items have many-to-many relationships with status. The tracker tables resolves these relationships in such a way that an item can have multiple entries in the tracker - each with a particular status.
I tried to upload a picture of the tables to make things clearer but alas, I don't have enough points yet :C
I need to find items whose last status in the Itemtracker table meets a condition, either '3' or '0'.
I then need to get the first one of these items.
The steps I am using to accomplish this are as follows:
Get all the Orders which have a certain status.
Get all the Items in that Order.
Get all the Items whose last status was = 0 or 3.
Get the first of these items.
My code is as follows:
public ITEM GetFirstItemFailedOrNotInProductionFromCurrentOrder()
{
var firstOrder = GetFirstOrderInProductionAndNotCompleted();
var items = ERPContext.ITEM.Where(i => i.OrderID == firstOrder.OrderID) as IQueryable<ITEM>;
if (CheckStatusOfItems(items) != null)
{
var nextItem = CheckStatusOfItems(items);
return nextItem ;
}
else
{
return null;
}
}
private ITEM CheckStatusOfItems(IQueryable<ITEM> items)
{
List<ITEM> listOfItemsToProduce = new List<ITEM>();
foreach (ITEM item in items.ToList())
{
var lastStatusOfItem = ERPContext.ITEMTRACKER.Where(it => it.ItemID == item.ItemID)
.OrderByDescending(it => it.ItemTrackerID).FirstOrDefault();
if (lastStatusOfItem.ItemStatus == (int)ItemStatus.Failed || lastStatusOfItem.ItemStatus == (int)ItemStatus.Confirmed)
{
listOfItemsToProduce.Add(item);
}
}
return listOfItemsToProduce.FirstOrDefault();
}
Now, this all works fine and returns what I need but I'm aware that this might not be the best approach. As it is now my IQueryable collection of items will never contain more than 6 items - but if it could grow larger, then calling ToList() on the IQueryable and iterating over the results in-memory would probably not be a good idea.
Is there a better way to iterate through the IQueryable items to fetch out the items that have a certain status as their latest status without calling ToList() and foreaching through the results?
Any advice would be much appreciated.
Using LINQ query syntax, you can build declaratively a single query pretty much the same way you wrote the imperative iteration. foreach translates to from, var to let and if to where:
private ITEM CheckStatusOfItems(IQueryable<ITEM> items)
{
var query =
from item in items
let lastStatusOfItem = ERPContext.ITEMTRACKER
.Where(it => it.ItemID == item.ItemID)
.OrderByDescending(it => it.ItemTrackerID)
.FirstOrDefault()
where (lastStatusOfItem.ItemStatus == (int)ItemStatus.Failed || lastStatusOfItem.ItemStatus == (int)ItemStatus.Confirmed)
select item;
return query.FirstOrDefault();
}
or alternatively using from instead of let and Take(1) instead of FirstOrDefault():
private ITEM CheckStatusOfItems(IQueryable<ITEM> items)
{
var query =
from item in items
from lastStatusOfItem in ERPContext.ITEMTRACKER
.Where(it => it.ItemID == item.ItemID)
.OrderByDescending(it => it.ItemTrackerID)
.Take(1)
where (lastStatusOfItem.ItemStatus == (int)ItemStatus.Failed || lastStatusOfItem.ItemStatus == (int)ItemStatus.Confirmed)
select item;
return query.FirstOrDefault();
}
Ok so I'm trying to get all items which have been shipped and add them to a list if the shipment item is not already in that list. But if the shipment item is found in the list then I want to combine those two items in the list.
Here is the code I'm working with:
var shippedItems = _orderService.GetOrderById(shipment.OrderId).Shipments.Where(x => x.ShippedDateUtc != null && x.OrderId == shipment.OrderId && x.Id != shipment.Id).ToList();
List<ShipmentItem> shipmentItemsList = new List<ShipmentItem>();
for (int i = 0; i <= shippedItems.Count - 1; i++)
{
var si = shippedItems[i];
var sii = si.ShipmentItems.ToList();
foreach (var item in sii)
{
if (!shipmentItemsList.Contains(item))
{
shipmentItemsList.Add(item);
}
else
{
var foundId = shipmentItemsList.Select(x => x.Id == item.Id);
shipmentItemsList.Aggregate((foundId, item) => foundId + item);
}
}
}
For these two variables (foundId, item) i get errors:
A local variable named the variable name cannot be declared in this
scope because that name is used in an enclosing local scope to define
a local or parameter
UPDATE
I also thought I could try the following, but it's not joining the results.
if (i == 0)
{
shipmentItemsList = si.ShipmentItems.ToList();
}
else
{
shipmentItemsList.Concat(si.ShipmentItems.ToList());
}
Anyone able to point me on the right track.
Cheers
Thanks for the clarification. Essentially, the way that I understand your problem is that you need to take an object map that is grouped by Shipment and look at it from the point of Item instead. Linq can deal with this for you by using SelectMany to flatten the list and the GroupBy to shape the flattened list into your new groupings. I've made some assumptions about property names for the nopCommerce objects, but the following code sample should get you close enough to tweak with the correct property names:
var shipmentItemsList = shippedItems // This is logically grouped by shipment id
.SelectMany(s => s.ShipmentItems) // First flatten the list
.GroupBy(i => i.ItemId) // Now group it by item id
.Select(g => new
{
ItemId = g.Key,
Quantity = g.Sum(item => item.Quantity)
}) // now get the quantity for each group
.ToList();