I want to group by the categoryid and then do a count on this. But I don't know how to do this. I have tried a couple of ways without success. Here is my latest:
public class Count
{
public int TradersCount { get; set; }
public int Id { get; set; }
public string Description { get; set; }
}
public IQueryable<Count> CountTradersAttachedToCategories()
{
var data = from tc in _db.tblTradersCategories
select new Count
{
Description = tc.tblCategory.description,
Id = tc.tblCategory.categoryId,
TradersCount = tc.Select(x => x.categoryid).GroupBy().Count()
};
return data;
}
tblTradersCategories joins both
tblTraders/tblCategories
A single trader can have many categories
A single category can have many traders
Thanks in advance for any help.
Clare
Try this:
var data = from tc in _db.tblTradersCategories
group tc by new { tc.tblCategory.categoryId,
tc.tblCategory.description } into g
select new { Count = g.Count(),
Id = g.Key.categoryId,
Description = g.Key.description };
If you want that in your Count class you may need to use AsEnumerable() to perform the conversion in process:
var converted = data.AsEnumerable()
.Select(c => new Count { TradersCount = c.Count,
Id = c.Id,
Description = c.Description });
You can try doing them all in one go:
var data = from tc in _db.tblTradersCategories
group tc by new { tc.tblCategory.categoryId,
tc.tblCategory.description } into g
select new Count { TradersCount = g.Count,()
Id = g.Key.categoryId,
Description = g.Key.description };
But I don't know if that will work. It depends on how the LINQ provider handles it.
Related
Using EF Core code-first, and I want to find any record with a similar list of a foreign entities to the entity I already have.
public class ClownModel {
public int Id { get; set; }
public List<CarModel> Cars { get; set; }
}
public class CarModel {
public int Id { get; set; }
}
var MyClown = new ClownModel() { /*add properties*/ }
//or maybe an existing record selected from database, just some ClownModel instance
Basically, "Select all the ClownModels where they have any Cars.Id that are in my MyClown.Cars"
Assuming that ClownModel has unique CarModel Id's, you can use the following query:
Matches All Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Count() == ids.Count
select cm;
Matches Any Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Any()
select cm;
i have the following LINQ
public IEnumerable<TurbineStatus> turStatus()
{
var result = (from s in _db.masterData
group s by s.current_turbine_status into g
select new TurbineStatus
{
status = g.Key,
numberOfTurbines = g.Count()
}
).ToList().OrderByDescending(s => s.status);
return result;
}
my class:
public class TurbineStatus
{
public string status { get; set; }
public int numberOfTurbines { get; set; }
public int allTurbines { get; set; }
}
i gives me the number of turbines according to the status,for example, 5turbines STOP,6 turbines RUN,10 turbines Link Down and so on,i also need to have sum of all these statuses,in my TurbinesStatus class i have a field which is int and named it allTurbines,how can i achieve it?
It's probably better for performance reasons to let the DB handle sorting and then once the result is materialized, you can extract the sum of the turbines count:
var result =
(
from s in _db.masterData
group s by s.current_turbine_status into g
select new TurbineStatus
{
status = g.Key,
numberOfTurbines = g.Count()
} into statusGroup
orderby statusGroup.status descending
select statusGroup
).ToList();
int totalTurbines = groups.Sum(statusGroup => statusGroup.numberOfTurbines);
To return both as a TurbinesStatus instance:
public class TurbinesStatus
{
public IReadOnlyList<TurbineStatus> TurbineStatuses { get; }
public int TotalCount { get; }
public TurbinesStatus(IReadOnlyList<TurbineStatus> turbineStatuses)
{
TurbineStatuses = turbineStatuses;
TotalCount = turbineStatuses.Sum(ts => ts.numberOfTurbines);
}
}
and then
public TurbinesStatus turStatus()
{
var statuses =
(
from s in _db.masterData
group s by s.current_turbine_status into g
select new TurbineStatus
{
status = g.Key,
numberOfTurbines = g.Count()
} into statusGroup
orderby statusGroup.status descending
).ToList();
return new TurbinesStatus(statuses);
}
As you can see, I got this error when I built Data Gird using Kendo UI. Does anybody could point out where I'm wrong in my code below.
private IEnumerable<Product> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.Select(p => new Product
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
}).ToList();
return subcate;
}
Error:
The entity or complex type 'AdventureWorks2012Model.Product' cannot be constructed in a LINQ to Entities query.
Thank you so much for your time!
Since Product is an entity of model, you are creating new object of this entity while selecting the records, which is NOT good idea, I am NOT sure how model will handle this kind of behaviour that is why it is preventing you to do so, (I guess). Anyway you can change the code to this,
private IEnumerable<Product> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.ToList();
return subcate;
}
BTW your function name indicating that you are missing a Where clause.
Also you can create some custom DTO class and use it instead.
E.g.
class ProductDTO
{
public int ProductID { get; set; }
public string Name { get; set; }
public string Color { get; set; }
public decimal ListPrice { get; set; }
}
private IEnumerable<ProductDTO> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.Select(p => new ProductDTO
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
}).ToList();
return subcate;
}
The first bad smell code I can point out for you. DBContext implements IDisposable so you are responsible for calling Dispose on it. In all, but one case in here, using block
You must build query to get all the product and then extract from it.
private IEnumerable<Product> GetSubProduct()
{
using (var context = new AdvenDBEntities())
{
// Get all constructed type product and then select from it
var subcate = context.Products
.ToList()
.Select(p => new Product
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
});
return subcate;
}
}
I selected 4 columns from my table by using select statement LINQ to SQL. Then I create a new List to store the query result. BUT, the code room.ToList(); is WRONG.
Why cannot we use "rooms_list = room.ToList()"?
How should we do to solve the problem???
Thanks for teaching me!
private void btnTest_Click(object sender, EventArgs e)
{
List<string> rooms_list = new List<string>();
using (LVDatabaseEntities database = new LVDatabaseEntities())
{
var room = from x in database.PHONGCHOIs
select new { x.TENPHONG, x.MATKHAUPHONG, x.CHUPHONG, x.SOLUONG };
rooms_list = room.ToList();
}
MessageBox.Show(rooms_list.Count.ToString());
}
Your rooms_list = room.ToList() is wrong, because it is not the List of type string.
To fix this, first create a class for a room
class Room
{
string TENPHONG { get; set; }
string MATKHAUPHONG { get; set; }
string CHUPHONG{ get; set; }
string SOLUONG{ get; set; }
}
Then, change your code like this
List<Room> rooms_list = new List<Room>();
using (LVDatabaseEntities database = new LVDatabaseEntities())
{
var rooms = from x in database.PHONGCHOIs
select new Room{
TENPHONG = x.TENPHONG,
MATKHAUPHONG = x.MATKHAUPHONG,
CHUPHONG = x.CHUPHONG,
SOLUONG = x.SOLUONG };
rooms_list = room.ToList();
}
MessageBox.Show(rooms_list.Count.ToString());
*Not tested. Let me know if anything didn't work
I've written a LINQ query shown below :
List<Actions> actions = resourceActions.Actions.Select(s => s.ActionName).ToList();
How do I give for selecting multiple columns here ? ie I want to add columns s.ActionId and s.IsActive. I'm unable to apply it.
Make a class to represent the data you want:
public class ResourceAction
{
public int Id {get;set;}
public string Name {get; set; }
}
Select a list of those instead:
List<ResourceAction> actions = resourceActions.Actions
.Select(s => new ResourceAction() { Id = s.Id, Name = s.ActionName}).ToList();
I believe this is what your looking for. However you need to change the output to an anonymous type.
var actions = resourceActions.Actions.Select(s => new { s.ActionName, s.ActionId, s.IsActive } ).ToList();
You can use a anonymous type for this, for example
var actions = resourceActions.Actions.Select(s =>
new { Id = s.Id, Name = s.ActionName, Active = s.IsActive).ToList();
but a better way would be to create a class like
public class ActionWithId
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
}
List<ActionWithId> actions = resourceActions.Actions.Select(s =>
new ActionWithId() { Id = s.Id, Name = s.ActionName, Active = s.IsActive }).ToList();