Here is the query I am trying to run from my OData source:
var query = from j in _auditService.AuditJobs.IncludeTotalCount()
orderby j.Description
select new
{
JobId = j.ID,
Description = j.Description,
SubscriberCount = j.JobRuns.Count()
};
It runs great if I don't use the j.JobRuns.Count(), but if I include it I get the following error:
Constructing or initializing instances
of the type
<>f__AnonymousType1`3[System.Int32,System.String,System.Int32]
with the expression j.JobRuns.Count()
is not supported.
It seems to be a problem of attempting to get the nested count through OData. What is a work around for this? I was trying to avoid getting the whole nested collection for each object just to get a count.
Thanks!
As of today the OData protocol doesn't support aggregates.
Projections yes, but projections that include aggregate properties no.
Alex
You need .Net 4.0 and In LinqPad you can run following over netflix OData Service
void Main()
{
ShowPeopleWithAwards();
ShowTitles();
}
// Define other methods and classes here
public void ShowPeopleWithAwards()
{
var people = from p in People.Expand("Awards").AsEnumerable()
where p.Awards.Count > 0
orderby p.Name
select new
{
p.Id,
p.Name,
AwardCount = p.Awards.Count,
TotalAwards = p.Awards.OrderBy (a => a.Type).Select (b => new { b.Type, b.Year} )
};
people.Dump();
}
public void ShowTitles()
{
var titles = from t in Titles.Expand("Awards").AsEnumerable()
where t.ShortName != string.Empty &&
t.ShortSynopsis != string.Empty &&
t.Awards.Count > 0
select t;
titles.Dump();
}
You can now use my product AdaptiveLINQ and the extension method QueryByCube.
Related
private void BindGrid()
{
AdvContextEF db = new AdvContextEF();
var query = from r in db.mytable
orderby r.CreateDate descending
select new
{
r.id,
r.code,
r.mytable.relatedtables[0].TheCenter.Name
};
RadGrid1.DataSource = query.ToList();
RadGrid1.DataBind();
}
I got the following error when running the code above.
LINQ to Entities does not recognize the method 'AdvContextEF.mymethod get_Item(Int32)' method, and this method cannot be translated into a store expression.
thank you
Instead of trying to index into r.mytable.relatedtables[0], try using .FirstOrDefault().
r.mytable.relatedtables.FirstOrDefault().TheCenter.Name
or
Name = r.mytable.relatedtables.Select(rt => rt.TheCenter.Name).FirstOrDefault()
I need to get the following code to work
public IQueryable<BankingDTO> Get(ODataQueryOptions<TillSummaryDTO> options)
{
return((IQueryable<BankingDTO>)options.ApplyTo(this._bankingService.GetBanking()));
}
I would like to query on TillSummaryDTO because it has the field "TillOpID" on it. However I would like to return BankingDTO as this is the end result which contains the group by and sum. When I run the query I receive the error "Cannot apply ODataQueryOptions of 'Bepoz.Presentation.ViewModels.TillSummaryDTO' to IQueryable of 'Bepoz.Presentation.ViewModels.BankingDTO" what is the best practice for this?
The bankingservice.GetBanking method looks like this
var query = from t in _tillSummaryRepository.Table
join w in _workStationRepository.Table on t.TillOpID equals w.WorkstationID
join s in _storeRepository.Table on w.StoreID equals s.StoreID
join v in _venueRepository.Table on s.VenueID equals v.VenueID
select new TillSummaryDTO
{
TillOpID = t.TillOpID,
Cash = t.Cash,
Workstation = new WorkstationDTO()
{
WorkstationID = w.WorkstationID,
Name = w.Name,
Store = new StoreDTO()
{
StoreID = s.StoreID,
StoreGroup = s.StoreGroup,
Name = s.Name,
Venue = new VenueDTO()
{
VenueID = v.VenueID,
VenueGroup = v.VenueGroup,
Name = v.Name,
}
}
}
};
return query.GroupBy(x => x.Workstation.Name)
.Select(x => new BankingDTO()
{
TotalCash = x.Sum(y => y.Cash),
WorkstationName = x.Key
});
The scenario you want to achieve is that you have an entity set of TillSummaryDTO that you want to query, and you would like the return type to be a collection of BankingDTO. The query for the BankingDTO is carried out by applying the query options in the URL onto TillSummaryDTO . But the fact that the BankingDTO and TillSummaryDTO are different kind of types makes it impossible achieve that in a simple Get action method, right?
This scenario can be better resolved by the function feature of the OData protocol that the function takes the TillSummaryDTO collection as input parameter, has some internal complicated logic to query for the right BankingDTO, and returns the BankingDTO instead of TillSummaryDTO.
For the concept of function in OData protocol, you can refer to this link for V4 and section "10.4.2. Functions" of this page for V3.
For implementation, this sample can be referred to for Web API OData V4 and this tutorial can be referred to for Web API OData V3.
I have the following LINQ query
QueryResult<List<PersonDemographic>> members = new QueryResult<List<PersonDemographic>>();
var query = (from ms in this.Session.Query<MemberSummary>()
where ms.NameSearch.StartsWith(firstName.ToUpper())
&& ms.NameSearch2.StartsWith(lastName.ToUpper())
select new PersonDemographic
{
FirstName = ms.FirstName.ToProperCase(),
LastName = ms.LastName.ToProperCase(),
PersonId = ms.Id,
Address = new Address
{
Line1 = ms.AddressLine1.ToProperCase(),
Line2 = ms.AddressLine2.ToProperCase(),
City = ms.City.ToProperCase(),
State = ms.State,
Zipcode = ms.Zipcode,
},
PhoneNumber = new PhoneNumber
{
Number = string.IsNullOrWhiteSpace(ms.PhoneNumber) ? null : Regex.Replace(ms.PhoneNumber, #"(\d{3})(\d{3})(\d{4})", "$1-$2-$3")
}
});
if (this.Session.Transaction.IsActive)
{
members.Data = query.Distinct().Take(15).ToList();
}
else
{
using (var transaction = this.Session.BeginTransaction())
{
members.Data = query.Distinct().Take(15).ToList();
transaction.Commit();
}
}
The code is running under the transaction section. If I use it without a Distinct I have no problem. Adding the Distinct gives me an exception
{"Expression type 10005 is not supported by this SelectClauseVisitor."}
I can't find anything definitive. Can anyone help?
Thanks,
Paul
There are lots of things in that query that NH can't possibly know how to translate to SQL:
ToProperCase (that looks like an extension method of yours)
string.IsNullOrWhiteSpace (that's new in .NET 4, NH is compiled against 3.5)
Regex.Replace (that's just not possible to do with SQL, unless you have a DB that supports it and write a Dialect for it)
I am having some trouble with a linq query I am trying to write.
I am trying to use the repository pattern without to much luck. Basically I have a list of transactions and a 2nd list which contains the description field that maps against a field in my case StoreItemID
public static IList<TransactionViewModel> All()
{
var result = (IList<TransactionViewModel>)HttpContext.Current.Session["Transactions"];
if (result == null)
{
var rewardTypes = BusinessItemRepository.GetItemTypes(StoreID);
HttpContext.Current.Session["Transactions"] =
result =
(from item in new MyEntities().TransactionEntries
select new TransactionViewModel()
{
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
}).ToList();
}
return result;
}
public static List<BusinessItemViewModel>GetItemTypes(int storeID)
{
var result = (List<BusinessItemViewModel>)HttpContext.Current.Session["ItemTypes"];
if (result == null)
{
HttpContext.Current.Session["ItemTypes"] = result =
(from items in new MyEntities().StoreItems
where items.IsDeleted == false && items.StoreID == storeID
select new BusinessItemViewModel()
{
ItemDescription = items.Description,
StoreID = items.StoreID,
StoreItemID = items.StoreItemID
}).ToList();
}
return result;
However I get this error
Unable to create a constant value of type 'MyMVC.ViewModels.BusinessItemViewModel'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
I know its this line of code as if I comment it out it works ok
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
How can I map ItemDescription against my list of itemTypes?
Any help would be great :)
This line has a problem:
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription,
Since you are using FirstOrDefault you will get null as default value for a reference type if there is no item that satifies the condition, then you'd get an exception when trying to access ItemDescription - either use First() if there always will be at least one match or check and define a default property value for ItemDescription to use if there is none:
ItemDescription = itemTypes.Any(r=>r.StoreItemID==item.StoreItemID)
? itemTypes.First(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription
: "My Default",
If itemTypes is IEnumerable then it can't be used in your query (which is what the error message is telling you), because the query provider doesn't know what to do with it. So assuming the that itemTypes is based on a table in the same db as TransactionEntities, then you can use a join to achieve the same goal:
using (var entities = new MyEntities())
{
HttpContext.Current.Session["Transactions"] = result =
(from item in new entities.TransactionEntries
join itemType in entities.ItemTypes on item.StoreItemID equals itemType.StoreItemID
select new TransactionViewModel()
{
ItemDescription = itemType.ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
CustomerName = rewards.CardID//TODO: Get customer name
}).ToList();
}
I don't know the structure of your database, but hopefully you get the idea.
I had this error due a nullable integer in my LINQ query.
Adding a check within my query it solved my problem.
query with problem:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.Equals(y.OBJ_ID));
query with problem solved:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.HasValue && s.Obj_Id.Value.Equals(y.OBJ_ID));
I have a variable size array of strings, and I am trying to programatically loop through the array and match all the rows in a table where the column "Tags" contains at least one of the strings in the array. Here is some pseudo code:
IQueryable<Songs> allSongMatches = musicDb.Songs; // all rows in the table
I can easily query this table filtering on a fixed set of strings, like this:
allSongMatches=allSongMatches.Where(SongsVar => SongsVar.Tags.Contains("foo1") || SongsVar.Tags.Contains("foo2") || SongsVar.Tags.Contains("foo3"));
However, this does not work (I get the following error: "A lambda expression with a statement body cannot be converted to an expression tree")
allSongMatches = allSongMatches.Where(SongsVar =>
{
bool retVal = false;
foreach(string str in strArray)
{
retVal = retVal || SongsVar.Tags.Contains(str);
}
return retVal;
});
Can anybody show me the correct strategy to accomplish this? I am still new to the world of LINQ :-)
You can use the PredicateBuilder class:
var searchPredicate = PredicateBuilder.False<Songs>();
foreach(string str in strArray)
{
var closureVariable = str; // See the link below for the reason
searchPredicate =
searchPredicate.Or(SongsVar => SongsVar.Tags.Contains(closureVariable));
}
var allSongMatches = db.Songs.Where(searchPredicate);
LinqToSql strange behaviour
I recently created an extension method for creating string searches that also allows for OR searches. Blogged about here
I also created it as a nuget package that you can install:
http://www.nuget.org/packages/NinjaNye.SearchExtensions/
Once installed you will be able to do the following
var result = db.Songs.Search(s => s.Tags, strArray);
If you want to create your own version to allow the above, you will need to do the following:
public static class QueryableExtensions
{
public static IQueryable<T> Search<T>(this IQueryable<T> source, Expression<Func<T, string>> stringProperty, params string[] searchTerms)
{
if (!searchTerms.Any())
{
return source;
}
Expression orExpression = null;
foreach (var searchTerm in searchTerms)
{
//Create expression to represent x.[property].Contains(searchTerm)
var searchTermExpression = Expression.Constant(searchTerm);
var containsExpression = BuildContainsExpression(stringProperty, searchTermExpression);
orExpression = BuildOrExpression(orExpression, containsExpression);
}
var completeExpression = Expression.Lambda<Func<T, bool>>(orExpression, stringProperty.Parameters);
return source.Where(completeExpression);
}
private static Expression BuildOrExpression(Expression existingExpression, Expression expressionToAdd)
{
if (existingExpression == null)
{
return expressionToAdd;
}
//Build 'OR' expression for each property
return Expression.OrElse(existingExpression, expressionToAdd);
}
}
Alternatively, take a look at the github project for NinjaNye.SearchExtensions as this has other options and has been refactored somewhat to allow other combinations
There is another, somewhat easier method that will accomplish this. ScottGu's blog details a dynamic linq library that I've found very helpful in the past. Essentially, it generates the query from a string you pass in. Here's a sample of the code you'd write:
Dim Northwind As New NorthwindDataContext
Dim query = Northwind.Products _
.Where("CategoryID=2 AND UnitPrice>3") _
.OrderBy("SupplierId")
Gridview1.DataSource = query
Gridview1.DataBind()
More info can be found at scottgu's blog here.
Either build an Expression<T> yourself, or look at a different route.
Assuming possibleTags is a collection of tags, you can make use of a closure and a join to find matches. This should find any songs with at least one tag in possibleTags:
allSongMatches = allSongMatches.Where(s => (select t from s.Tags
join tt from possibleTags
on t == tt
select t).Count() > 0)