For some reason I am unable to use Select() after a Skip()/Take() unless I do this in a certain way. The following code works and allows me to use result as part of a sub query.
var query = QueryOver.Of<MyType>();
query.Skip(1);
var result = query.Select(myType => myType.Id);
However, if I attempt to create the query on one line as below I can't compile.
var query = QueryOver.Of<MyType>().Skip(1);
var result = query.Select(myType => myType.Id);
It looks like the code in the first results in query being of type QueryOver< MyType, MyType> while the second results in query being of type QueryOver< MyType>.
It also works if written like this.
var query = QueryOver.Of<MyType>().Select(myType => myType.Id).Skip(1);
Any ideas why the second version fails horribly when the first and third versions work? It seems like odd behavior.
You have a typo in the second version...
var query = QueryOver.Of<MyType().Skip(1);
is missing the >
var query = QueryOver.Of<MyType>().Skip(1);
Not sure if thats what you where looking for.
Related
The following code is giving the above error, and I cannot figure out why:
var x = _sqlConn.Connection().QueryResults<Results>("MyDb.dbo.get_records", new { id = theId });
int retVal = x.Outputs.Return_Value;
if (retVal == 0) // ...meaning result set was also returned...fine to this point.
{
var list = x.Outputs.Set1; // exception thrown here with above error
var temp = list.FirstOrDefault();
I have been using other features of Insight.Database for a number of years, but have not had to retrieve a SQL RETURN value at the same time as a recordset. The SQL itself works correctly in SSMS, returning a result set and the RETURN value of 0, as expected. This is happening in VS2019, .NET 4 and .NET 4.5.2; Insight.Database 5.2.7 and 5.2.8.
I got this code from the following page:
https://github.com/jonwagner/Insight.Database/wiki/Specifying-Result-Structures
where it shows this:
var results = connection.QueryResults<Beer, Glass>("GetAllBeersAndAllGlasses");
IList<Beer> beers = results.Set1;
which I combined with the following code from here:
https://github.com/jonwagner/Insight.Database/wiki/Output-Parameters
var results = connection.QueryResults<Results>("MyProc", inputParameters);
var p = results.Outputs.p;
That part works. It's accessing .Set1 that is failing, and I am not sure how to track down why.
I do not have experience with the FastExpando class, but Jon promised magic, and I want to believe. Thanks for any help.
I haven’t tried results+dynamic objects in a while…
I think it is because you are doing:
QueryResults<Results> and Results is an Insight type
You probably want:
QueryResults<MyType>
And then you get back a Results<MyType>
Which contains the return val and Set1
If not, post a ticket over on github and we will help you out.
My Linq Query keeps returning the null error on FirstOrDefault
The cast to value type 'System.Int32' failed because the materialized value is null
because it can't find any records to match on the ClinicalAssetID form the ClinicalReading Table, fair enough!
But I want the fields in my details page just to appear blank if the table does not have matching entry.
But how can I handle the null issue when using the order by function ?
Current Code:
var ClinicalASSPATINCVM = (from s in db.ClinicalAssets
join cp in db.ClinicalPATs on s.ClinicalAssetID equals cp.ClinicalAssetID into AP
from subASSPAT in AP.DefaultIfEmpty()
join ci in db.ClinicalINSs on s.ClinicalAssetID equals ci.ClinicalAssetID into AI
from subASSINC in AI.DefaultIfEmpty()
join co in db.ClinicalReadings on s.ClinicalAssetID equals co.ClinicalAssetID into AR
let subASSRED = AR.OrderByDescending(subASSRED => subASSRED.MeterReadingDone).FirstOrDefault()
select new ClinicalASSPATINCVM
{
ClinicalAssetID = s.ClinicalAssetID,
AssetTypeName = s.AssetTypeName,
ProductName = s.ProductName,
ModelName = s.ModelName,
SupplierName = s.SupplierName,
ManufacturerName = s.ManufacturerName,
SerialNo = s.SerialNo,
PurchaseDate = s.PurchaseDate,
PoNo = s.PoNo,
Costing = s.Costing,
TeamName = s.TeamName,
StaffName = s.StaffName,
WarrantyEndDate = subASSPAT.WarrantyEndDate,
InspectionDate = subASSPAT.InspectionDate,
InspectionOutcomeResult = subASSPAT.InspectionOutcomeResult,
InspectionDocumnets = subASSPAT.InspectionDocumnets,
LastTypeofInspection = subASSINC.LastTypeofInspection,
NextInspectionDate = subASSINC.NextInspectionDate,
NextInspectionType = subASSINC.NextInspectionType,
MeterReadingDone = subASSRED.MeterReadingDone,
MeterReadingDue = subASSRED.MeterReadingDue,
MeterReading = subASSRED.MeterReading,
MeterUnitsUsed = subASSRED.MeterUnitsUsed,
FilterReplaced = subASSRED.FilterReplaced
}).FirstOrDefault(x => x.ClinicalAssetID == id);
Tried this but doesn't work
.DefaultIfEmpty(new ClinicalASSPATINCVM())
.FirstOrDefault()
Error was:
CS1929 'IOrderedEnumerable<ClinicalReading>' does not contain a definition for 'DefaultIfEmpty' and the best extension method overload 'Queryable.DefaultIfEmpty<ClinicalASSPATINCVM>(IQueryable<ClinicalASSPATINCVM>, ClinicalASSPATINCVM)' requires a receiver of type 'IQueryable<ClinicalASSPATINCVM>'
Feel a little closer with this but still errors
let subASSRED = AR.OrderByDescending(subASSRED => (subASSRED.MeterReadingDone != null) ? subASSRED.MeterReadingDone : String.Empty).FirstOrDefault()
Error:
CS0173 Type of conditional expression cannot be determined because there is no implicit conversion between 'System.DateTime?' and 'string'
The original error means that some of the following properties of the ClinicalASSPATINCVM class - MeterReadingDone, MeterReadingDue, MeterReading, MeterUnitsUsed, or FilterReplaced is of type int.
Remember that subASSRED here
let subASSRED = AR.OrderByDescending(subASSRED => subASSRED.MeterReadingDone).FirstOrDefault()
might be null (no corresponding record).
Now look at this part of the projection:
MeterReadingDone = subASSRED.MeterReadingDone,
MeterReadingDue = subASSRED.MeterReadingDue,
MeterReading = subASSRED.MeterReading,
MeterUnitsUsed = subASSRED.MeterUnitsUsed,
FilterReplaced = subASSRED.FilterReplaced
If that was LINQ to Objects, all these would generate NRE (Null Reference Exception) at runtime. In LINQ to Entities this is converted and executed as SQL. SQL has no issues with expression like subASSRED.SomeProperty because SQL supports NULL naturally even if SomeProperty normally does not allow NULL. So the SQL query executes normally, but now EF must materialize the result into objects, and the C# object property is not nullable, hence the error in question.
To solve it, find the int property(es) and use the following pattern inside query:
SomeIntProperty = (int?)subASSRED.SomeIntProperty ?? 0 // or other meaningful default
or change receiving object property type to int? and leave the original query as is.
Do the same for any non nullable type property, e.g. DateTime, double, decimal, Guid etc.
You're problem is because your DefaultIfEmpty is executed AsQueryable. Perform it AsEnumerable and it will work:
// create the default element only once!
static readonly ClinicalAssPatInVcm defaultElement = new ClinicalAssPatInVcm ();
var result = <my big linq query>
.Where(x => x.ClinicalAssetID == id)
.AsEnumerable()
.DefaultIfEmpty(defaultElement)
.FirstOrDefault();
This won't lead to a performance penalty!
Database management systems are extremely optimized for selecting data. One of the slower parts of a database query is the transport of the selected data to your local process. Hence it is wise to let the DBMS do most of the selecting, and only after you know that you only have the data that you really plan to use, move the data to your local process.
In your case, you need at utmost one element from your DBMS, and if there is nothing, you want to use a default object instead.
AsQueryable will move the selected data to your local process in a smart way, probably per "page" of selected data.
The page size is a good compromise: not too small, so you don't have to ask for the next page too often; not too large, so that you don't transfer much more items than you actually use.
Besides, because of the Where statement you expect at utmost one element anyway. So that a full "page" is fetched is no problem, the page will contain only one element.
After the page is fetched, DefaultIfEmpty checks if the page is empty, and if so, returns a sequence containing the defaultElement. If not, it returns the complete page.
After the DefaultIfEmpty you only take the first element, which is what you want.
I am new to jayData and am trying to filter on an entity set. The filter needs to perform an complex evaluation beyond what I saw in the samples.
Here is a working sample of what I am trying to accomplish (the listView line isn't and is just there to show what I plan to do with the data):
function () {
var weekday = moment().isoWeekday()-1;
console.log(weekday);
var de = leagueDB.DailyEvents.toArray(function (events) {
console.log(events);
var filtered = [];
for (var e = 0; e < events.length;e++) {
console.log(events[e]);
console.log(events[e].RecurrenceRule);
var rule = RRule.fromString(events[e].RecurrenceRule);
var ruleOptions = rule.options.byweekday;
var isDay = ruleOptions.indexOf(weekday);
console.log(ruleOptions, isDay);
if(isDay =! -1)
{
filtered.push(events[e]);
}
}
$("#listView").kendoListView({dataSource:filtered});
});
Basically it is just evaluating a recurring rule string to see if the current day meets that criteria, if so add that event to the list for viewing.
But it blows up when I try to do this:
eventListLocal:leagueDB.DailyEvents.filter(function(e){
console.log("The Weekday is:"+viewModel.weekday);
console.log(e);
console.log("The recurrence rule is:"+e.RecurrenceRule);
var rruleOptions = viewModel.rruleOptions(e.RecurrenceRule);
if (rruleOptions !== -1) {
return true;
}
}).asKendoDataSource()
The error that is generating is:
Exception: Unable to resolve type:undefined
The thing is it seems to be occurring on "e" and the console logs like the event is not being passed in. However, I am not seeing a list either. In short I am really confused as to what is going on.
Any help would be appreciated.
Thanks,
You can't write filter expressions such as this.
When you write .filter(...), jaydata will parse your expression and then it will generate filter for underlying provider, for example where for webSql and $filter for oDataProvider.
Both JayData expression parser and the data provider itself should understand your filter.
Your filter is not suitable for this approach, because most of your codes are not familiar for jaydata expression parser and the underlying data provider, for example your console.log etc.
You can simplify your filter, or you should load all your data into an array, and then you can use filter method of array itself, there, you can write any filter you like, and your filter will work. Of course this has performance issue in some scenarios when your data set is large.
Read more on http://jaydata.org/tutorials/entityexpressions-the-heart-of-jaydata
I'm using logical deletes by adding a field deletedAt. If I want to get only the deleted documents it would be something like r.table('clients').hasFields('deletedAt'). My method has a withDeletes parameter which determines if deleted documents are excluded or not.
Finally, people at the #rethinkdb IRC channel suggested me to use the filter method and that did the trick:
query = adapter.table(table).filter(filters)
if withDeleted
query = adapter.filter (doc) ->
return doc.hasFields 'deletedAt'
else
query = adapter.filter (doc) ->
return doc.hasFields('deletedAt').not()
query.run connection, (err, results) ->
...
My question is why do I have to use filter and not something like:
query = adapter.table(table).filter(filters)
query = if withDeleted then query.hasFields 'deletedAt' else query.hasFields('deletedAt').not()
...
or something like that.
Thanks in advance.
The hasFields function can be called on both objects and sequences, but not cannot.
This query:
query.hasFields('deletedAt')
Behaves the same as this one (on sequences of objects):
query.filter((doc) -> return doc.hasFields('deletedAt'))
However, this query:
query.hasFields('deletedAt').not()
Behaves like this:
query.filter((doc) -> return doc.hasFields('deletedAt')).not()
But that doesn't make sense. you want the not to be inside the filter, not after it. Like this:
query.filter((doc) -> return doc.hasFields('deletedAt').not())
One nice that about RethinkDB is that because of the way queries are built up in host language it's very easy to define new fluent syntax by just defining functions in your language. For example if you wanted to have a lacksFields function you could define it in Python (sorry I don't really know coffeescript) like so:
def lacks_fields(stream, *args):
res = stream
for arg in args:
res = res.filter(lambda x: ~x.has_fields(arg))
return res
Then you can use a nice fluent syntax like:
lacks_fields(stream, "foo", "bar", "buzz")
This seems like it should be so easy, but I've tried three or four ways to do it (but to no avail).
I'm just trying to put a query result in a viewbag and display it.
I've tried putting a model object list in a ViewBag:
var mesg = from MSG in lemondb.Messages
where MSG.msg == Membership.GetUser().ToString()
select MSG;
ViewBag.messages = MSG;
And then I try to spit it out in a .cshtml:
var message = (List<LemonTrader.Models.Message>)ViewBag.messages; // <--- fails here because it is a string
foreach ( var MSG in message )
{
#Html.Label(MSG.msg)<br />
}
But it says:
Cannot convert type
'System.Data.Entity.Infrastructure.DbQuery'
to
'System.Collections.Generic.List'
So it seems I'm using using the wrong template. How do I spit out a System.Entity.Infrastructure.DbQuery?
I've also tried passing the results through the Viewbag as a list of strings. (Is that a worse way to do it?)
var mesg = from MSG in lemondb.Messages
where MSG.msg == Membership.GetUser().ToString()
select MSG.msg;
ViewBag.messages = mesg;
And spitting it out as a string list:
foreach (var atext in ViewBag.messages as List<string>) { // gets hung up on foreach here (why???)
#Html.Label( atext )
}
And I get this:
Object reference not set to an
instance of an object.
And it points at the "foreach" keyword.
Does that mean there were no messages? Or what?
I wish there was a tutorial showing how to put queryresults in a ViewBag and how to get them out! I've seen tutorials that return an object.ToList() without respect to any kind of "where" mechanism, but no examples to pull out a few, relevant entries and display them.
Try
ViewBag.messages = MSG.ToList();
Also, System.Data.Entity.Infrastructure.DbQuery implements IEnumerable ( http://msdn.microsoft.com/en-us/library/system.data.entity.infrastructure.dbquery(v=vs.103).aspx ) so this should also work:
var message = (IEnumerable<LemonTrader.Models.Message>)ViewBag.messages;