I'm trying to develop a tiny front-end for a sqlite DB using Razor Pages (NOT MVC!).
Looks like it supports SQL in a different way, not like I used to in the past.
For example, I need to re-assign value to the field Pl_Pos (position of the record in the list). Now I do this like that:
for (int i = PlnPos + 1; i<= PlModelIndexModel.PlnModelTotal; i++)
{
PlnModel PlnModelRedo = await _context.Plane_Models.FirstOrDefaultAsync(m => m.Pl_Model_Pos == i);
PlnModelRedo.Pl_Model_Pos = i - 1;
_context.Attach(PlnModelRedo).State = EntityState.Modified;
await _context.SaveChangesAsync();
}
Is there any other way to do it more efficient and do something like:
Update Pl_Models set Pl._Models.Pl_Pos = Pl_Models set Pl._Models.Pl_Pos - 1 where Pl_Models set Pl._Models.Pl_Pos > PlnPos
I stuck a bit...
Thanks in advance!
I'm not entirely sure what you're asking but it sounds like
you're just after a LINQ statement or foreach loop.
var PlaneModels = _context.Plane_Models.ToList();
foreach(PlaneModel pm in PlaneModels)
{
PlaneModel.Pl_Model_Pos -= 1;
}
_context.Plane_Models.UpdateRange(PlaneModels);
await _context.SaveChangesAsync();
When are you trying to modify the position of the record in the list? When a record is inserted/appended/deleted, or is it used as a display index?
Related
_context.Update(v) ;
_context.SaveChanges();
When I use this code then SQL Server adds a new record instead of updating the
current context
[HttpPost]
public IActionResult PageVote(List<string> Sar)
{
string name_voter = ViewBag.getValue = TempData["Namevalue"];
int count = 0;
foreach (var item in Sar)
{
count = count + 1;
}
if (count == 6)
{
Vote v = new Vote()
{
VoteSarparast1 = Sar[0],
VoteSarparast2 = Sar[1],
VoteSarparast3 = Sar[2],
VoteSarparast4 = Sar[3],
VoteSarparast5 = Sar[4],
VoteSarparast6 = Sar[5],
};
var voter = _context.Votes.FirstOrDefault(u => u.Voter == name_voter && u.IsVoted == true);
if (voter == null)
{
v.IsVoted = true;
v.Voter = name_voter;
_context.Add(v);
_context.SaveChanges();
ViewBag.Greeting = "رای شما با موفقیت ثبت شد";
return RedirectToAction(nameof(end));
}
v.IsVoted = true;
v.Voter = name_voter;
_context.Update(v);
_context.SaveChanges();
return RedirectToAction(nameof(end));
}
else
{
return View(_context.Applicants.ToList());
}
}
You need to tell the DbContext about your entity. If you do var vote = new Vote() vote has no Id. The DbContext see this and thinks you want to Add a new entity, so it simply does that. The DbContext tracks all the entities that you load from it, but since this is just a new instance, it has no idea about it.
To actually perform an update, you have two options:
1 - Load the Vote from the database in some way; If you get an Id, use that to find it.
// Loads the current vote by its id (or whatever other field..)
var existingVote = context.Votes.Single(p => p.Id == id_from_param);
// Perform the changes you want..
existingVote.SomeField = "NewValue";
// Then call save normally.
context.SaveChanges();
2 - Or if you don't want to load it from Db, you have to manually tell the DbContext what to do:
// create a new "vote"...
var vote = new Vote
{
// Since it's an update, you must have the Id somehow.. so you must set it manually
Id = id_from_param,
// do the changes you want. Be careful, because this can cause data loss!
SomeField = "NewValue"
};
// This is you telling the DbContext: Hey, I control this entity.
// I know it exists in the DB and it's modified
context.Entry(vote).State = EntityState.Modified;
// Then call save normally.
context.SaveChanges();
Either of those two approaches should fix your issue, but I suggest you read a little bit more about how Entity Framework works. This is crucial for the success (and performance) of your apps. Especially option 2 above can cause many many issues. There's a reason why the DbContext keep track of entities, so you don't have to. It's very complicated and things can go south fast.
Some links for you:
ChangeTracker in Entity Framework Core
Working with Disconnected Entity Graph in Entity Framework Core
I am trying to create a sort by feature for "recommended" on my ecommerce site using the orderBy method. Here's a sample of a simple orderby:
if($params['sortby'] == 'numpricehl') $query->orderBy('price','desc');
What I am hoping to do is order by rotating values. Example: Given 10 products priced at: (10,20,30,....100), it would order them like this (low,mid,high,low,mid,high) etc. so that the products would display like this (10,50,100,20,60,80)
What would be the best way to go about doing this?
Here's a solution that works on the query result:
$tiers = 3;
$result = [];
$products = Product::orderBy('price')->get();
$size = ceil($products->count() / $tiers);
$split = $products->pluck('price')->chunk($size);
while(!$split[0]->isEmpty()) {
for($tier = 0; $tier < $tiers; $tier++) {
if(!$split[$tier]->isEmpty()) {
$result[] = $split[$tier]->shift();
}
}
}
There's probably an in-database solution with orderBy(), but I'm pretty sure it's more complicated.
The chunk() part isn't ideal yet because it splits 10 products into 4,4,2.
You can add this to get 4,3,3:
if($products->count() % $tiers == 1) {
$split[2]->prepend($split[1]->pop());
}
I use sqlJdbs query as a data provider for my CCC controls. I use geospatial request in my query that's why I cache my results(Cache=True). Otherwise the request made long.
It works fine. However I have to use parameters in my query to filter resulting rows:
SELECT ...
FROM ...
WHERE someField IN (${aoi_param})
Is there some way to cache full set of rows and then apply WHERE to cached results without rebuilding new cache for each set of values in the ${aoi_param}?
What is the best practice?
So, I am not really sure that it is the best practice, but I solved my problem this way:
I included aoi_param to the Listeners and Parameters of my chart control
Then I filtered data set in Post Fetch:
function f(data){
var _aoi_param = this.dashboard.getParameterValue('${p:aoi_param}');
function isInArray(myValue, myArray) {
var arrayLength = myArray.length;
for (var i = 0; i < arrayLength; i++) {
if (myValue == myArray[i]) return true;
}
return false;
}
function getFiltered(cdaData, filterArray) {
var allCdaData = cdaData;
cdaData = {
metadata: allCdaData.metadata,
resultset: allCdaData.resultset.filter(function(row){
// 2nd column is an AOI id in my dataset
return isInArray(row[2], filterArray);
})
};
return cdaData;
}
var dataFiltered = getFiltered(data, _aoi_param);
return dataFiltered;
}
excluded WHERE someField IN (${aoi_param}) from the query of my sql over sqlJdbc component
Using Entity Framework, I am updating about 300 rows, and 9 columns about every 30 seconds. Below is how I am currently doing it. My question is, how can I make the code more efficient?
Every once in a while, I feel my database gets hit with the impact and I just want to make it as efficient as possible.
// FOREACH OF MY 300 ROWS
var original = db.MarketDatas.FirstOrDefault(x => x.BBSymbol == targetBBsymbol);
if (original != null)
{
//if (original.BBSymbol.ToUpper() == "NOH7 INDEX")
//{
// var x1 = 1;
//}
original.last_price = marketDataItem.last_price;
original.bid = marketDataItem.bid;
original.ask = marketDataItem.ask;
if (marketDataItem.px_settle_last_dt_rt != null)
{
original.px_settle_last_dt_rt = marketDataItem.px_settle_last_dt_rt;
}
if (marketDataItem.px_settle_actual_rt != 0)
{
original.px_settle_actual_rt = marketDataItem.px_settle_actual_rt;
}
original.chg_on_day = marketDataItem.chg_on_day;
if (marketDataItem.prev_close_value_realtime != 0)
{
original.prev_close_value_realtime = marketDataItem.prev_close_value_realtime;
}
if (marketDataItem.px_settle_last_dt_rt != null)
{
DateTime d2 = (DateTime)marketDataItem.px_settle_last_dt_rt;
if (d1.Day == d2.Day)
{
//market has settled
original.settled = "yes";
}
else
{
//market has NOT settled
original.settled = "no";
}
}
if (marketDataItem.updateTime.Year != 1)
{
original.updateTime = marketDataItem.updateTime;
}
db.SaveChanges();
}
Watching what is being hit in the debugger...
SELECT TOP (1)
[Extent1].[MarketDataID] AS [MarketDataID],
[Extent1].[BBSymbol] AS [BBSymbol],
[Extent1].[Name] AS [Name],
[Extent1].[fut_Val_Pt] AS [fut_Val_Pt],
[Extent1].[crncy] AS [crncy],
[Extent1].[fut_tick_size] AS [fut_tick_size],
[Extent1].[fut_tick_val] AS [fut_tick_val],
[Extent1].[fut_init_spec_ml] AS [fut_init_spec_ml],
[Extent1].[last_price] AS [last_price],
[Extent1].[bid] AS [bid],
[Extent1].[ask] AS [ask],
[Extent1].[px_settle_last_dt_rt] AS [px_settle_last_dt_rt],
[Extent1].[px_settle_actual_rt] AS [px_settle_actual_rt],
[Extent1].[settled] AS [settled],
[Extent1].[chg_on_day] AS [chg_on_day],
[Extent1].[prev_close_value_realtime] AS [prev_close_value_realtime],
[Extent1].[last_tradeable_dt] AS [last_tradeable_dt],
[Extent1].[fut_notice_first] AS [fut_notice_first],
[Extent1].[updateTime] AS [updateTime]
FROM [dbo].[MarketDatas] AS [Extent1]
WHERE ([Extent1].[BBSymbol] = #p__linq__0) OR (([Extent1].[BBSymbol] IS NULL) AND (#p__linq__0 IS NULL))
It seems it updates the same thing multiple times, if I am understanding it correctly.
UPDATE [dbo].[MarketDatas]
SET [last_price] = #0, [chg_on_day] = #1, [updateTime] = #2
WHERE ([MarketDataID] = #3)
UPDATE [dbo].[MarketDatas]
SET [last_price] = #0, [chg_on_day] = #1, [updateTime] = #2
WHERE ([MarketDataID] = #3)
You can reduce this to 2 round trips.
Don't call SaveChanges() in side the loop. Move it outside and call it after you are done processing everything.
Write the select in such a way that it retrieves all the originals in one go and pushes them to a memory collection, then retrieve from that for each item you are updating/inserting.
code
// use this as your source
// to retrieve an item later use TryGetValue
var originals = db.MarketDatas
.Where(x => arrayOftargetBBsymbol.Contains(x.BBSymbol));
.ToDictionary(x => x.BBSymbol, y => y);
// iterate over changes you want to make
foreach(var change in changes){
MarketData original = null;
// is there an existing entity
if(originals.TryGetValue(change.targetBBsymbol, out original)){
// update your original
}
}
// save changes all at once
db.SaveChanges();
You could only execute "db.SaveChanges" after your foreach loop. It think it you would do exactly what your are asking for.
It seems it updates the same thing multiple times, if I am
understanding it correctly.
Entity Framework performs a database round-trip for every entity to update.
Just check the parameter value, they will be different.
how can I make the code more efficient
The major problem is your current solution is not scalable.
It works well when you only have a few entities to update but will become worse and worse are the number of items to update in a batch will increase.
It's often better to make this kind of logic all in the database, but perhaps you cannot do it.
Disclaimer: I'm the owner of the project Entity Framework Extensions
This library can make your code more efficient by allowing you to save multiples entities at once. All bulk operations are supported:
BulkSaveChanges
BulkInsert
BulkUpdate
BulkDelete
BulkMerge
BulkSynchronize
Example:
// Easy to use
context.BulkSaveChanges();
// Easy to customize
context.BulkSaveChanges(bulk => bulk.BatchSize = 100);
// Perform Bulk Operations
context.BulkDelete(customers);
context.BulkInsert(customers);
context.BulkUpdate(customers);
// Customize Primary Key
context.BulkMerge(customers, operation => {
operation.ColumnPrimaryKeyExpression =
customer => customer.Code;
});
So I have a standard service reference proxy calss for MS CRM 2013 (i.e. right-click add reference etc...) I then found the limitation that CRM data calls limit to 50 results and I wanted to get the full list of results. I found two methods, one looks more correct, but doesn't seem to work. I was wondering why it didn't and/or if there was something I'm doing incorrectly.
Basic setup and process
crmService = new CrmServiceReference.MyContext(new Uri(crmWebServicesUrl));
crmService.Credentials = System.Net.CredentialCache.DefaultCredentials;
var accountAnnotations = crmService.AccountSet.Where(a => a.AccountNumber = accountNumber).Select(a => a.Account_Annotation).FirstOrDefault();
Using Continuation (something I want to work, but looks like it doesn't)
while (accountAnnotations.Continuation != null)
{
accountAnnotations.Load(crmService.Execute<Annotation>(accountAnnotations.Continuation.NextLinkUri));
}
using that method .Continuation is always null and accountAnnotations.Count is always 50 (but there are more than 50 records)
After struggling with .Continutation for a while I've come up with the following alternative method (but it seems "not good")
var accountAnnotationData = accountAnnotations.ToList();
var accountAnnotationFinal = accountAnnotations.ToList();
var index = 1;
while (accountAnnotationData.Count == 50)
{
accountAnnotationData = (from a in crmService.AnnotationSet
where a.ObjectId.Id == accountAnnotationData.First().ObjectId.Id
select a).Skip(50 * index).ToList();
accountAnnotationFinal = accountAnnotationFinal.Union(accountAnnotationData).ToList();
index++;
}
So the second method seems to work, but for any number of reasons it doesn't seem like the best. Is there a reason .Continuation is always null? Is there some setup step I'm missing or some nice way to do this?
The way to get the records from CRM is to use paging here is an example with a query expression but you can also use fetchXML if you want
// Query using the paging cookie.
// Define the paging attributes.
// The number of records per page to retrieve.
int fetchCount = 3;
// Initialize the page number.
int pageNumber = 1;
// Initialize the number of records.
int recordCount = 0;
// Define the condition expression for retrieving records.
ConditionExpression pagecondition = new ConditionExpression();
pagecondition.AttributeName = "address1_stateorprovince";
pagecondition.Operator = ConditionOperator.Equal;
pagecondition.Values.Add("WA");
// Define the order expression to retrieve the records.
OrderExpression order = new OrderExpression();
order.AttributeName = "name";
order.OrderType = OrderType.Ascending;
// Create the query expression and add condition.
QueryExpression pagequery = new QueryExpression();
pagequery.EntityName = "account";
pagequery.Criteria.AddCondition(pagecondition);
pagequery.Orders.Add(order);
pagequery.ColumnSet.AddColumns("name", "address1_stateorprovince", "emailaddress1", "accountid");
// Assign the pageinfo properties to the query expression.
pagequery.PageInfo = new PagingInfo();
pagequery.PageInfo.Count = fetchCount;
pagequery.PageInfo.PageNumber = pageNumber;
// The current paging cookie. When retrieving the first page,
// pagingCookie should be null.
pagequery.PageInfo.PagingCookie = null;
Console.WriteLine("#\tAccount Name\t\t\tEmail Address");while (true)
{
// Retrieve the page.
EntityCollection results = _serviceProxy.RetrieveMultiple(pagequery);
if (results.Entities != null)
{
// Retrieve all records from the result set.
foreach (Account acct in results.Entities)
{
Console.WriteLine("{0}.\t{1}\t\t{2}",
++recordCount,
acct.EMailAddress1,
acct.Name);
}
}
// Check for more records, if it returns true.
if (results.MoreRecords)
{
// Increment the page number to retrieve the next page.
pagequery.PageInfo.PageNumber++;
// Set the paging cookie to the paging cookie returned from current results.
pagequery.PageInfo.PagingCookie = results.PagingCookie;
}
else
{
// If no more records are in the result nodes, exit the loop.
break;
}
}