I am creating a gridview that will be populated based upon a linq statement, the sql is as follows:
SELECT TOP 10 IDDesc, UnitUserfield1, UnitUserfield2, ProductPercentage
FROM tblOnlineReportingCOMPLETEWeights
WHERE (MaterialLevel = 'Primary') AND (MaterialText = 'Paper')
ORDER BY ProductPercentage DESC
Now, what I would like to do is let the user specify the Top 10, so essentially it is a "Top x" this being defined in a textbox i.e. they type in 50 into the textbox, the linq query is executed and the gridview displays the top 50.
I understand that using Take is the area I want to look at, is this correct? Is this even possible?!
Any thoughts, muchly appreciated.
PS: apologies for asking thick questions, I am very new to all of this!
You are correct. Take user input and feed it to Take. That'll do.
int howMany = Convert.ToInt32 (HowManyTextBox.Value);
var queryResult = /*.....*/.Take (howMany);
int max = 0;
if (Int.TryParse(TextBox1.Text, out max)
{
var q = (from tbl where ... orderby ... desc).Take(max);
}
Along those lines
Thank you all so much, I went with the following:
{
ORWeightsDataClassesDataContext db = new ORWeightsDataClassesDataContext();
int max = 0;
if (int.TryParse(txtbxHowMany.Text, out max))
{
var queryV = db.tblOnlineReportingCOMPLETEWeights
.Where(x => x.MaterialLevel == "Primary" && x.MaterialText == "Paper")
.OrderByDescending(x => x.ProductPercentage).Take(max);
GridView1.DataSource = queryV;
GridView1.DataBind();
}
}
It works a treat.
Thank so so much, very grateful and now my site is finally coming together...I feel liek celebrating...pub anyone?!
Related
I am not able to fetch a max value from a number field in AppMaker. The field is filled with unique integers from 1 and up. In SQL I would have asked like this:
SET #tKey = (SELECT MAX(ID) FROM GiftCard);
In AppMaker I have done the following (with a bit help from other contributors in this forum) until now, and it returns tKey = "NaN":
var tKey = google.script.run.MaxID();
function MaxID() {
var ID_START_FROM = 11000;
var lock = LockService.getScriptLock();
lock.waitLock(3000);
var query = app.models.GiftCard.newQuery();
query.sorting.ID._descending();
query.limit = 1;
var records = query.run();
var next_id = records.length > 0 ? records[0].ID : ID_START_FROM;
lock.releaseLock();
return next_id;
}
There is also a maxValue() function in AppMaker. However, it seems not to work in that way I use it. If maxvalue() is better to use, please show :-)
It seems that you are looking in direction of auto incremented fields. The right way to achieve it would be using Cloud SQL database. MySQL will give you more flexibility with configuring your ids:
ALTER TABLE GiftCard AUTO_INCREMENT = 11000;
In case you strongly want to stick to Drive Tables you can try to fix your script as follow:
google.script.run
.withSuccessHandler(function(maxId) {
var tKey = maxId;
})
.withFailureHandler(function(error) {
// TODO: handle error
})
.MaxID();
As a side note I would also recommend to set your ID in onBeforeCreate model event as an extra security layer instead of passing it to client and reading back since it can be modified by malicious user.
You can try using Math.max(). Take into consideration the example below:
function getMax() {
var query = app.models.GiftCard.newQuery();
var allRecords = query.run();
allIds = [];
for( var i=0; i<allRecords.length;i++){
allIds.push(allRecords[i].ID);
}
var maxId = Math.max.apply(null, allIds);
return maxId;
}
Hope it helps!
Thank you for examples! The Math.max returned an undefined value. Since this simple case is a "big" issue, I will solve this in another way. This value is meant as a starting value for a sequence only. An SQL base is better yes!
how would I restrict the "Charges" returned in this linq query, to a specified date range:
var dte = DateTime.Parse("2012-01-01");
var dte2 = DateTime.Parse("2012-02-01");
var meetingrooms = tblMeetingRoom
.Where(r => r.building_id==1)
.GroupBy(p => p.tblType)
.Select(g => new
{
TypeName = g.Key.room_type,
TypeID = g.Key.type_id,
TypeCount = g.Count(),
charges =
from rt in charges
where (rt.type_id == g.Key.type_id)
select new {
rt.chargedate,
rt.people,
rt.charge
}
});
meetingrooms.Dump();
I think it needs to go inbetween here somehwhere:
from rt in charges
where (rt.type_id == g.Key.type_id) (EG) && rt.chargedate>=dte and rt.chargedate <dte2
select new {
Thanks for any help,
Mark
from rt in charges
where rt.type_id == g.Key.type_id && (rt.chargedate >= dte && rt.chargedate <= dte2)
select new {
.....
#Maarten - I've been trying this for ages - LinqPad kept giving errors, so I was trying all different ways I could think of - for whatever reason, I must have made some typos, that I didn't make above!
Sorry for wasting everyone's time - the above works "as-is"!
Mark
I want to extract part of a collection to another collection.
I can easily do the same using a for loop, but my linq query is not working for the same.
I am a neophyte in Linq, so please help me correcting the query (if possible with explanation / beginners tutorial link)
Legacy way of doing :
Collection<string> testColl1 = new Collection<string> {"t1", "t2", "t3", "t4"};
Collection<string> testColl2 = new Collection<string>();
for (int i = 0; i < newLength; i++)
{
testColl2.Add(testColl1[i]);
}
Where testColl1 is the source & testColl2 is the desired truncated collection of count = newLength.
I have used the following linq queries, but none of them are working ...
var result = from t in testColl1 where t.Count() <= newLength select t;
var res = testColl1.Where(t => t.Count() <= newLength);
Use Enumerable.Take:
var testColl2 = testColl1.Take(newLength).ToList();
Note that there's a semantic difference between your for loop and the version using Take. The for loop will throw with IndexOutOfRangeException exception if there are less than newLength items in testColl1, whereas the Take version will silently ignore this fact and just return as many items up to newLength items.
The correct way is by using Take:
var result = testColl1.Take(newLength);
An equivalent way using Where is:
var result = testColl1.Where((i, item) => i < newLength);
These expressions will produce an IEnumerable, so you might also want to attach a .ToList() or .ToArray() at the end.
Both ways return one less item than your original implementation does because it is more natural (e.g. if newLength == 0 no items should be returned).
You could convert to for loop to something like this:
testColl1.Take(newLength)
Use Take:
var result = testColl1.Take(newLength);
This extension method returns the first N elements from the collection where N is the parameter you pass, in this case newLength.
I have a linq query like this:
var accounts =
from account in context.Accounts
from guranteer in account.Gurantors
where guranteer.GuarantorRegistryId == guranteerRegistryId
select new AccountsReport
{
recordIndex = ?
CreditRegistryId = account.CreditRegistryId,
AccountNumber = account.AccountNo,
}
I want to populate recordIndex with the value of current row number in collection returned by the LINQ. How can I get row number ?
Row number is not supported in linq-to-entities. You must first retrieve records from database without row number and then add row number by linq-to-objects. Something like:
var accounts =
(from account in context.Accounts
from guranteer in account.Gurantors
where guranteer.GuarantorRegistryId == guranteerRegistryId
select new
{
CreditRegistryId = account.CreditRegistryId,
AccountNumber = account.AccountNo,
})
.AsEnumerable() // Moving to linq-to-objects
.Select((r, i) => new AccountReport
{
RecordIndex = i,
CreditRegistryId = r.CreditRegistryId,
AccountNumber = r.AccountNo,
});
LINQ to objects has this builtin for any enumerator:
http://weblogs.asp.net/fmarguerie/archive/2008/11/10/using-the-select-linq-query-operator-with-indexes.aspx
Edit: Although IQueryable supports it too (here and here) it has been mentioned that this does unfortunately not work for LINQ to SQL/Entities.
new []{"aap", "noot", "mies"}
.Select( (element, index) => new { element, index });
Will result in:
{ { element = aap, index = 0 },
{ element = noot, index = 1 },
{ element = mies, index = 2 } }
There are other LINQ Extension methods (like .Where) with the extra index parameter overload
Try using let like this:
int[] ints = new[] { 1, 2, 3, 4, 5 };
int counter = 0;
var result = from i in ints
where i % 2 == 0
let number = ++counter
select new { I = i, Number = number };
foreach (var r in result)
{
Console.WriteLine(r.Number + ": " + r.I);
}
I cannot test it with actual LINQ to SQL or Entity Framework right now. Note that the above code will retain the value of the counter between multiple executions of the query.
If this is not supported with your specific provider you can always foreach (thus forcing the execution of the query) and assign the number manually in code.
Because the query inside the question filters by a single id, I think the answers given wont help out. Ofcourse you can do it all in memory client side, but depending how large the dataset is, and whether network is involved, this could be an issue.
If you need a SQL ROW_NUMBER [..] OVER [..] equivalent, the only way I know is to create a view in your SQL server and query against that.
This Tested and Works:
Amend your code as follows:
int counter = 0;
var accounts =
from account in context.Accounts
from guranteer in account.Gurantors
where guranteer.GuarantorRegistryId == guranteerRegistryId
select new AccountsReport
{
recordIndex = counter++
CreditRegistryId = account.CreditRegistryId,
AccountNumber = account.AccountNo,
}
Hope this helps.. Though its late:)
We have classes
public Invoice: EntityObject
{
public EntityCollection<InvoicePosition> Positions { get {...}; set{...}; }
...
}
public InvoicePosition: EntityObject
{
public string GroupName { get {...}; set{...}; }
}
We are given IQueryable<Invoice>, we are not given IQueryable<InvoicePosition>. How should I find invoices that have positions, where GroupName is 'Fuel'?
IQueryable<Invoice> invoices = InvoiceRepository.List();
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
where ?
select i
EntityFramework should be able to translate it to proper sql query.
EDIT
As Mark Seemann wrote, I can use:
IQueryable<Invoice> invoices = InvoiceRepository.List().Include("Positions").Include("OtherInclude");
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
from p in i.Positions
where p.GroupName = 'Fuel'
select i;
There is a problem. When I use this filtering, I lose "OtherInclude". I think that this is not proper way of filtering when using EF. I'll have to change it to:
IQueryable<Invoice> invoices = InvoiceRepository.List().Include("Positions").Include("OtherInclude");
IQueryable<Invoice> invoicesThatHaveFuelPositions = invoices.Where(???);
But what should I write in Where?
EDIT
Changed Include("Position") to Include("Positions").
EDIT
Alex James gave link to the tip (http://blogs.msdn.com/alexj/archive/2009/06/02/tip-22-how-to-make-include-really-include.aspx), which suggests:
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
where i.Positions.Any(p => p.GroupName == 'Fuel')
select i;
It seems to work and doesn't influence EF includes.
Building on Marks answer. If you do this:
var q = from i in invoices.Include("something")
from p in i.Positions
where p.GroupName == "Fuel"
select i;
The include is lost (see this tip) because the EF loses all includes if the shape of the query changes, for example if you do implicit joins like in a SelectMany query, aka from from.
The workaround is to write your query, and then at the end apply the Include.
Something like this:
var q = ((from i in invoices
from p in i.Positions
where p.GroupName == "Fuel"
select i) as ObjectQuery<Invoice>).Include("something");
If you do this the Entity Framework actually does the include.
Hope this helps
Alex
Something like this ought to work:
var q = from i in invoices
from p in i.Positions
where p.GroupName == "Fuel"
select i;
However, that uses the navigation property Positions, which by default isn't loaded (the Entity Framework uses explicit loading). It will, however, work, if the invoices variable was created like this:
var invoices = from i in myObjectContext.Invoices.Include("Positions")
select i;