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()
});
Related
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);
}
I have the following query that groups locations and the average item cost and I would like to write it as one query but I cannot figure out the syntax. What LINQ do I need to do this? I have tried writing it different ways but the syntax is not correct.
var joinedData =
from r in shops
join i in items on r.shopId equals i.shopId
select new
{
Region = r.Location,
ItemCost = i.ItemCost
};
var AverageCostByLocation = joinedData
.GroupBy(m => new { m.Location})
.Select(m => new
{
Location= m.Key.Location,
AverageItemCost = m.Average(x => x.ItemCost)
});
Well, if you put first expression in parenthesis it should allow to join both expressions as they are. Also I'd probably get rid of second anonymous type for perfomance reasons (the new { m.Location} line is redundant, you might want to use .Key instead) :
var AverageCostByLocation =
(from r in shops
join i in items on r.shopId equals i.shopId
select new
{
Region = r.Location,
ItemCost = i.ItemCost
})
.GroupBy(m => m.Location)
.Select(m => new
{
Location= m.Key,
AverageItemCost = m.Average(x => x.ItemCost)
});
In the Linq to Entities query below I need to place a default value in the x.Number in the returned value if the query returns 0 OfficeTelephone objects. I have tried
x.Number??"555-1212" but that throws an error.
from c in Contacts
.Where(a => a.LastName.Contains("ANDUS")).Take(10)
select new
{
Id = c.Id,
OfficeTelephone = c.Telephones.Where(a=>a.TelephoneType.Name.Contains("Office")).Select(x => new { x.AreaCode, x.Number, x.TelephoneType, x.Primary })
}
I've tried something like:
from c in Contacts
.Where(a => a.LastName.Contains("ANDUS")).Take(10)
select new
{
Id = c.Id,
OfficeTelephone = c.Telephones
.Where(a=>a.TelephoneType.Name.Contains("Office"))
.Select(x => new { x.AreaCode, x.Number, x.TelephoneType, x.Primary })
.DefaultIfEmpty()}
But I'm not sure how to push a default object into the DefaultIFEmpty()
Use DefaultIfEmpty and pass a default instance with those value which you would want by default i.e. if no rows are returned.
try it like this:
Contacts.Where(a=>a.LastName.Contains("ANDUS"))
.Take(10)
.Select(x => new
{
Id = x.Id,
OfficeTelephone = x.Telephones
.Where(a=> a.Telephone.Name.Contains("Office"))
.Select(b=> new Telephone
{
b.AreaCode,
b.Number,
b.TelephoneType,
b.Primary
})
.DefaultIfEmpty(new Telephone())
});
where I've assumed that typeof(x.Telephones) == typeof(List<Telephone>)
I have the following LINQ query which uses NHibernate against a SQL Server backed repository...
var casesByCaseOwner = this.preGrantDetailRepository.All
.Where(x => x.CaseFileLocation.Id == cflId)
.GroupBy(x => x.CaseOwner)
.Select(x => new StagSummaryForCfItem
{
Id = x.Key.Id,
Description = x.Key.Name,
NumberOfCases = x.Count(),
UninvoicedNetFee = x.Sum(y => y.UninvoicedNetFee),
UninvoicedDisbursement = x.Sum(y => y.UninvoicedDisbursement)
}).AsEnumerable();
However, it complains that SQL Server is unable to group by the CaseOwner.Name column because it is not contained in the select list or group clause. Coming from a database world I understand that error, however, I'm not sure how to force NHibernate to group by both Id and Name but still have the CaseOwner entity available to me in my Select.
I found the answer finally...
var casesByCaseOwner = this.preGrantDetailRepository.All
.Where(x => x.CaseFileLocation.Id == cflId)
.GroupBy(x => new { x.CaseOwner.Id, x.CaseOwner.Name })
.Select(x => new StagSummaryForCfItem
{
Id = x.Key.Id,
Description = x.Key.Name,
NumberOfCases = x.Count(),
UninvoicedNetFee = x.Sum(y => y.UninvoicedNetFee),
UninvoicedDisbursement = x.Sum(y => y.UninvoicedDisbursement)
}).AsEnumerable();
return casesByCaseOwner;
This works nicley, it turns out I need to project a new entity with the properties I want to group on.
I'm using LINQ to manipulate a datatable. I have 3 columns - I would like group by one and then select the remaining 2 columns together. At the moment I have something like this
var query = reportDataTable.AsEnumerable()
.GroupBy(c => c["Code"])
.Select(g =>
new {
Code = g.Key,
Rank = g.Select(f => new
{ f["rank"],
f["Name"]}).ToArray()
});
but I get issues due to anonymous types. I know this syntax would work if I could reference the the column headers directly (in say a list or w/e). How can I get around this with DataTables? Cheers.
Edit:
Well I'd like to be able to reference the fields later when I come to populate the data into a different datatable:
foreach (var q in query)
{
DataRow df = dp.NewRow();
df["Code"] = q.Code;
foreach (var rank in q.Rank)
{
df[rank.name] = rank.rank;
}
dp.Rows.Add(df);
}
define your Rank fields, Also if you have a class for it, call related class constructor,
you can see this in bellow code, before ToArray.
var query = reportDataTable.AsEnumerable()
.GroupBy(c => c["Code"])
.Select(g =>
new { Code = g.Key, Rank =
g.Select(f => new { rank = f["rank"], name = f["Name"]})
.ToArray() });