I need to filter some Entities by various fields using "normal" WHERE and IN clauses in a query over my database, but I do not know how to do that with EF.
This is the approach:
Database table
Licenses
-------------
license INT
number INT
name VARCHAR
...
desired SQL Query in EF
SELECT * FROM Licenses WHERE license = 1 AND number IN (1,2,3,45,99)
EF Code
using (DatabaseEntities db = new DatabaseEntities ())
{
return db.Licenses.Where(
i => i.license == mylicense
// another filter
).ToList();
}
I have tried with ANY and CONTAINS, but I do not know how to do that with EF.
How to do this query in EF?
int[] ids = new int[]{1,2,3,45,99};
using (DatabaseEntities db = new DatabaseEntities ())
{
return db.Licenses.Where(
i => i.license == mylicense
&& ids.Contains(i.number)
).ToList();
}
should work
Related
I use Linq to Sql.
I have three table.
tabl_Region: from this table returning .ToList() via county column == 85
tabl_Season: from this table returning .ToList() via startdate >= today
tabl_Desc: from this table returning int [] ID via fldRegion== 1 results && fldSeason== 2 results
I will try to explain not worked codes
TurkusEntities context = new TurkusEntities();
return context.tabl_AttrDesc.Where(c => c.fldRegionId == context.tabl_Region.Where(r => r.fldCounty == 85).ToList() && c.fldSeasonId == context.tabl_Season.Where(s => s.fldStartDate >= DateTime.Now).ToList()).ToList;
I know i can solve it by using loops, but if it is possible i want to use only query.
If you are using Linq2Sql you can get the
sql that is generated by a linq query. with this command.
dc.GetCommand(query).CommandText
If you are using SQL Server Profiler inside the Sql Server (Tools --> SQL Server Profiler)
I found solution but not impossible in one query.
First I got int [] ID arrays which match conditions from two tables.After I wrote a query which provide control column data from arrays.
TurkusEntities context = new TurkusEntities();
Region region = new Region();
string[] dataarray = region.GetAllRegionsBySomeRule(RegionX);
var _db= context.tabl_AttrDesc.Where(c =>dataarray.Contains(c.fldRegionId.ToString().Trim())).ToList();
And Region
public string[] GetAllRegionsBySomeRule(int fldType,int fldRegionX)
{
TurkusEntities context = new TurkusEntities();
var _db = context.tabl_Region.Where(c => c.fldTown.Contains(fldRegionX.ToString())).ToList();
foreach (var data in _db)
{
Regions.Add(data.fldId.ToString().Trim());
}
string[] IDS = Regions.ToArray();
return IDS;
}
I have some errors using Linq on DataTable and I couldn't figure it out how to solve it. I have to admit that i am pretty new to Linq and I searched the forum and Internet and couldn't figure it out. hope you can help.
I have a DataTable called campaign with three columns: ID (int), Product (string), Channel (string). The DataTable is already filled with data. I am trying to select a subset of the campaign records which satisfied the conditions selected by the end user. For example, the user want to list only if the Product is either 'EWH' or 'HEC'. The selection criteria is dynaically determined by the end user.
I have the following C# code:
private void btnClick()
{
IEnumerable<DataRow> query =
from zz in campaign.AsEnumerable()
orderby zz.Field<string>("ID")
select zz;
string whereClause = "zz.Field<string>(\"Product\") in ('EWH','HEC')";
query = query.Where(whereClause);
DataTable sublist = query.CopyToDataTable<DataRow>();
}
But it gives me an error on line: query = query.Where(whereClause), saying
No property or field 'zz' exists in type 'DataRow'".
If I changed to:
string whereClause = "Product in ('EWH','HEC')"; it will say:
No property or field 'Product' exists in type 'DataRow'
Can anyone help me on how to solve this problem? I feel it could be a pretty simple syntax change, but I just don't know at this time.
First, this line has an error
orderby zz.Field<string>("ID")
because as you said, your ID column is of type int.
Second, you need to learn LINQ query syntax. Forget about strings, the same way you used from, orderby, select in the query, you can also use where and many other operators. Also you'll need to learn the equivalent LINQ constructs for SQL-ish things, like for instance IN (...) is mapped to Enumerable.Contains etc.
With all that being said, here is your query
var productFilter = new[] { "EWH", "HEC" };
var query =
from zz in campaign.AsEnumerable()
where productFilter.Contains(zz.Field<string>("Product"))
orderby zz.Field<int>("ID")
select zz;
Update As per your comment, if you want to make this dynamic, then you need to switch to lambda syntax. Multiple and criteria can be composed by chaining multiple Where clauses like this
List<string> productFilter = ...; // coming from outside
List<string> channelFilter = ...; // coming from outside
var query = campaign.AsEnumerable();
// Apply filters if needed
if (productFilter != null && productFilter.Count > 0)
query = query.Where(zz => productFilter.Contains(zz.Field<string>("Product")));
if (channelFilter != null && channelFilter.Count > 0)
query = query.Where(zz => channelFilter.Contains(zz.Field<string>("Channel")));
// Once finished with filtering, do the ordering
query = query.OrderBy(zz => zz.Field<int>("ID"));
I am using this query:
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
NoPublications = oi.Publications.Count(),
...
};
BlaInteraction contains an IList of publications (i.e. entities). To determine the number of publications one does not really need to do all the joins for a publication. Can I prevent nhibernate from using joins in the generated sql (e.g. using projection???) somehow?
Thanks.
Christian
PS:
This is what NH produces (slightly adapted):
select cast(count(*) as INT) from RelationshipStatementPublications publicatio21_, Publication publicatio22_ inner join Statements publicatio22_1_ on publicatio22_.StatementId=publicatio22_1_.DBId where publicatio21_.StatementId = 22762181 and publicatio21_.PublicationId=publicatio22_.StatementId
This is what would be sufficient:
select cast(count(*) as INT) from RelationshipStatementPublications publicatio21_ where publicatio21_.StatementId = 22762181
Why can't you just create another query ?
Session.QueryOver<Publication>().Where(x => x.BlaInteractionId == idSentAsParameter).Select(Projections.RowCount()).SingleOrDefault<int>();
I think that's will work
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
NoPublications = Session.QueryOver<Publication>().Where(x => x.BlaInteractionId == oi.Id).Select(Projections.RowCount()).SingleOrDefault<int>();
...
};
Another edit, have you tried lazy="extra" ?
Ok the best solution I have found so far is to use a FNH Formula:
mapping.Map(x => x.NOPublications).Formula("(select count(distinct RelationshipStatementPublications.PublicationId) from RelationshipStatementPublications where RelationshipStatementPublications.StatementId = DBId)");
public virtual int NOPublications {get; private set;}
when I map from the domain to the view model I use:
NoPublications = oi.NOPublications,
Christian
I'm trying to use LINQ to query the following Entity Data Model
based on this db model
I'd like to be able to pull a list of products based on ProductFacets.FacetTypeId.
Normally, I'd use joins and this wouldn't be a problem but I don't quite understand how to query many-to-many tables under the Entity DataModel.
This is an example sql query:
select p.Name, pf.FacetTypeId from Products p
inner join ProductFacets pf on p.ProductId = pf.ProductId
where pf.FacetTypeId in(8, 12)
Presuming EF 4:
var facetIds = new [] { 8, 12 };
var q = from p in Context.Products
where p.FacetTypes.Any(f => facetIds.Contains(f.FacetTypeId))
select p;
In EF (assuming the mapping is done correctly), joins are hardly ever used; navigation properties are used instead.
Your original SQL returns a tuple with repeated Name entries. With LINQ, it's often easier
to "shape" the queries into non-tuple results.
The following should be the same as the SQL, only instead of returning (Name, FacetTypeId) pairs with repeated Names, it will return a type that has a Name and a sequence of FacetTypeIds:
var facetIds = new [] { 8, 12 };
var result = from p in db.Products
select new
{
p.Name,
FacetTypeIds = from pf in p.FacetTypes
where pf.FacetTypeId == 8 || pf.FacetTypeId == 12
select pf.FacetTypeId,
};
Is there a pattern using Linq to dynamically create a filter?
I have the need to create custom filtering on a list, in the past I would just dynamically create the SQL...it doesn't seem like this is possible with Linq.
Check out the Dynamic Linq Library from ScottGu's blog:
For example, below is a standard type-safe LINQ to SQL VB query that retrieves data from a Northwind database and displays it in a ASP.NET GridView control:
Dim Northwind As New NorthwindDataContext
Dim query = From q In Northwind.Products Where p.CategoryID = 2 And p.UnitPrice > 3 Order By p.SupplierID Select p
Gridview1.DataSource = query
GridView1.DataBind()
Using the LINQ DynamicQuery library I could re-write the above query expression instead like so
Dim Northwind As New NorthwindDataContext
Dim query = Northwind.Products .where("CategoryID=2 And UnitPrice>3") . OrderBy("SupplierId")
Gridview1.DataSource = query
GridView1.DataBind()
Notice how the conditional-where clause and sort-orderby clause now take string expressions instead of code expressions. Because they are late-bound strings I can dynamically construct them. For example: I could provide UI to an end-user business analyst using my application that enables them to construct queries on their own (including arbitrary conditional clauses).
Dynamic Linq is one way to go.
It may be overkill for your scenario. Consider:
IQueryable<Customer> query = db.Customers;
if (searchingByName)
{
query = query.Where(c => c.Name.StartsWith(someletters));
}
if (searchingById)
{
query = query.Where(c => c.Id == Id);
}
if (searchingByDonuts)
{
query = query.Where(c => c.Donuts.Any(d => !d.IsEaten));
}
query = query.OrderBy(c => c.Name);
List<Customer> = query.Take(10).ToList();
Dynamically Composing Expression Predicates
something like this?
var myList = new List<string> { "a","b","c" };
var items = from item in db.Items
where myList.Contains(item.Name)
select item;
that would create a sql statement like
SELECT * FROM Items [t0] where Name IN ('a','b','c')