I have a Windows forms application (.NET 4.0) running with a Sql Server CE 3.5 database, which I access via an EF connection.
Here is my initial query, which returns two results:
var list = db.UserPresentation
.Select(up => new
{
UserPresentationID = up.UserPresentationID,
PresentationName = up.PresentationName,
DateRequested = up.DateRequested,
Edit = string.Empty,
Delete = string.Empty,
Download = string.Empty
})
.OrderByDescending(up => up.DateRequested)
.ToList();
Now I introduce an external variable and a where clause, and it returns zero results. If I run this same code in LinqPad, it returns 2 results.
int userID = 2;
// load list of user presentations
var list = db.UserPresentation
.Where(up => up.UserID == userID)
.Select(up => new
{
UserPresentationID = up.UserPresentationID,
PresentationName = up.PresentationName,
DateRequested = up.DateRequested,
Edit = string.Empty,
Delete = string.Empty,
Download = string.Empty
})
.OrderByDescending(up => up.DateRequested)
.ToList();
Now I hardcode the userid inside the query, and it returns two results again:
var list = db.UserPresentation
.Where(up => up.UserID == 2)
.Select(up => new
{
UserPresentationID = up.UserPresentationID,
PresentationName = up.PresentationName,
DateRequested = up.DateRequested,
Edit = string.Empty,
Delete = string.Empty,
Download = string.Empty
})
.OrderByDescending(up => up.DateRequested)
.ToList();
I'm really stumped. Any idea what's going on here?
Is UserID nullable?
If so be sure to do .Where(up => up.UserID.HasValue && up.UserID.Value == userID)
I had something similar with a nullable datetime once
Have you tried assigning the same hard coded value inside your variable? My guess is that the value in your variable is not found among your data, that is if you are sure that the variable name is correct.
Related
I'm implementing ASP.NET Core project and have a query like the following for finding count of distinct userId per operatorName, however it shows me error for the line count distinct after running the project:
var activeUserPerOperatorCount = requests.GroupBy(x => new { operatorName = x.Operator.Name, x.UserId }).Select(x => new
{
userIds = x.Key.UserId,
operatorNames = x.Key.operatorName,
activeUserPerOperatorCount = x.Select(l => l.UserId).Distinct().Count()
}).ToList();
I appreciate if anyone helps me how can I find distinct count of userId per operatorName in my query.
ok, the correct query is like the following and it works correctly:
var activeUserPerOperatorCount = requests.GroupBy(x => new { operatorName = x.Operator.Name}).Select(x => new
{
operatorNames = x.Key.operatorName,
activeUserPerOperatorCount = requests.Select(l => l.UserId).Distinct().Count()
}).ToList();
my linq method system from EF6 is returning $ref when I monitor results in fiddler. If I watch the local window in my webapi everything is populated correctly, but not in the actual results that are returned. It only affects the nested entries. anyone know what I am doing wrong? (I created models from database in EF6)
var student = dbEF.Accounts
.Where(x => x.AccountNumber == acctNum)
.Select(x => new DTOCrmDetails()
{
AccountNumber = x.AccountNumber,
CommissionId = x.CommissionId,
Commission = x.Commission,
ManagerID = x.ManagerID,
ManagerName = x.Manager.ManagerName,
Manager = x.Manager,
Employees = x.Manager.Employees,
WireInstructionsUSD = x.Manager.WireInstructionsUSDs
//Mapping_ManagersExecutingBrokers = x.Manager.Mapping_ManagersExecutingBrokers
}).FirstOrDefault();
return student;
these are my settings.
var json = config.Formatters.JsonFormatter; json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects; config.Formatters.Remove(config.Formatters.XmlFormatter); config.Formatters.JsonFormatter.SerializerSettings.Formatting = Newtonsoft.Json.Formatting.Indented; config.Formatters.JsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
You need to disable your lazy loading in the entity framework dbcontext.
something like this way:
dbEF.Configuration.LazyLoadingEnabled = false;
So I have my View setup like this in the controller:
public ActionResult View(Guid projectID)
{
OnboardModel model = context.onboard_projectInfos.Where(x => x.projectID == projectID).Select(x =>
new OnboardModel()
{
propertymanagername = x.propertymanagername,
propertymanagercontactemail = x.propertymanagercontactemail,
date_modified = (DateTime)x.date_modified,
projectmanagercontactnumber = x.projectmanagercontactnumber,
Developer = x.onboard_projectCreate.Developer,
status1 = x.onboard_projectCreate.status1,
ProjectName = x.onboard_projectCreate.ProjectName
}).SingleOrDefault();
var pix = projectID.ToString();
context.onboard_BuildingInfos.Where(x => x.buildprojectID == pix).GroupBy(x => x.buildprojectID).Select(g => {
model.totalres = g.Sum(b => b.numberofres);
model.totalcom = g.Sum(b => b.numberofcommer);
});
return View(model);
}
Problem is grabbing the sum of numberofres and numberofcommer from BuildingInfos.
Using .Select gives me the error:
Error CS0411 The type arguments for method 'Queryable.Select(IQueryable, Expression>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
How to I write this LINQ statement correctly?
Thanks.
You cannot modify an object within a select (you can only create a new object). Further, you can't add new properties to an existing object.
We'll assume that OnboardModel defines the totalres and totalcom properties.
var query = context.onboard_BuildingInfos
.Where(x => x.buildprojectID == pix)
.GroupBy(x => x.buildprojectID);
foreach(var g in query)
{
model.totalres = g.Sum(b => b.numberofres);
model.totalcom = g.Sum(b => b.numberofcommer);
}
As the title states, I'm trying to perform a select subquery in Linq-To-SQL. Here's my situation:
I have a database view which returns the following fields:
SourceId
LicenseId
LicenseName
CharacteristicId
CharacteristicName
Now I want to be able to store this in a model of mine which has the following properties
Id
Name
Characteristics (this is List which has Id, Name and Icon => Icon is byte[])
Here's the query I wrote which doesn't work:
var licensesWithCharacteristics =
_vwAllLicensesWithAttributesAndSourceIdRepository.GetAll()
.Where(x => x.SourceID == sourceId)
.Select(a => new LicenseWithCharacteristicsModel()
{
LicenseId = a.LicenseId,
LicenseName = a.LicenseName
,CharacteristicList = _vwAllLicensesWithAttributesAndSourceIdRepository.GetAll()
.Where(x => x.LicenseId == a.LicenseId)
.Select(c => new CharacteristicModel { Id = c.CharacteristicID, Name = c.CharacteristicName, Icon = c.Icon })
.Distinct().ToList()
})
.Distinct().ToList();
How would you solve this? I'm trying to do this in one query to keep my performance up, but I'm kind of stuck.
Your sample query and models are not that coherent (where does Icon come from, Characteristics or CharacteristicList), but anyway.
I do this in two parts, you can of course regroup this in one query.
I enumerate the result after the grouping, you may try to do without enumerating (all in linq to sql, but not sure it will work).
var groupedResult =
_vwAllLicensesWithAttributesAndSourceIdRepository.GetAll()
.Where(x => x.SourceID == sourceId)
.GroupBy(m => new {m.LicenseId, m.LicenseName})
.ToList();
var results = groupedResult.Select(group => new LicenseWithCharacteristicsModel {
LicenseId = group.Key.LicenseId,
LicenseName = group.Key.LicenseName,
Characteristics = group.Select(m=> new CharacteristicModel {
Id = m.CharacteristicId,
Name = m.CharacteristicName
}).ToList()
});
in "single query"
_vwAllLicensesWithAttributesAndSourceIdRepository.GetAll()
.Where(x => x.SourceID == sourceId)
.GroupBy(m => new {m.LicenseId, m.LicenseName})
.Select(group =>
new LicenseWithCharacteristicsModel
{
LicenseId = group.Key.LicenseId,
LicenseName = group.Key.LicenseName,
Characteristics = group.Select(m =>
new CharacteristicModel
{
Id = m.CharacteristicId,
Name = m.CharacteristicName
}).ToList()
});
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));