For the given data set, I want to return the unique rows for each OrderId that has the lowest number for Status, so the result would be:
I have a working query that does that:
var result = _dbContext.Orders
.GroupBy(s => s.OrderId)
.Select(group => group.OrderBy(x => x.Status).First()).ToList();
However, I would like to modify this query to only return three selected fields for each table row, rather than the dozens that exist. I know I need to add something like this:
.Select(group => new
{
OrderId = ???,
Status = ???,
Date = ???
}
But I am unable to add this to my existing query and have it still work. How can I do this?
You can try to do something like this:
var result = _dbContext.Orders
.GroupBy(s => s.OrderId)
.Select(group => group.OrderBy(x => x.Status).First())
.Select(order => new
{
OrderId = order.OrderId,
Status = order.Status,
Date = order.Date
})
.ToList();
In SQL you'd use:
SELECT OrderID,MIN(Status) as Status
FROM Orders
GROUP BY OrderID
A LINQ query is similar:
var query = context.Orders
.GroupBy(o=>o.OrderId)
.Select(g=> new {
OrderId=g.Key.OrderId,
Status=g.Min(o=>o.Status)
});
var results=query.ToList();
Related
Consider the following LINQ statements:
var model = getModel();
// apptId is passed in, not the order, so get the related order id
var order = (model.getMyData
.Where(x => x.ApptId == apptId)
.Select(y => y.OrderId));
var orderId = 0;
var orderId = order.LastOrDefault();
// see if more than one appt is associated to the order
var apptOrders = (model.getMyData
.Where(x => x.OrderId == orderId)
.Select(y => new { y.OrderId, y.AppointmentsId }));
This code works as expected, but I could not help but think that there is a more efficient way to accomplish the goal ( one call to the db ).
Is there a way to combine the two LINQ statements above into one? For this question please assume I need to use LINQ.
You can use GroupBy method to group all orders by OrderId. After applying LastOrDefault and ToList will give you the same result which you get from above code.
Here is a sample code:
var apptOrders = model.getMyData
.Where(x => x.ApptId == apptId)
.GroupBy(s => s.OrderId)
.LastOrDefault().ToList();
Entity Framework can't translate LastOrDefault, but it can handle Contains with sub-queries, so lookup the OrderId as a query and filter the orders by that:
// apptId is passed in, not the order, so get the related order id
var orderId = model.getMyData
.Where(x => x.ApptId == apptId)
.Select(y => y.OrderId);
// see if more than one appt is associated to the order
var apptOrders = model.getMyData
.Where(a => orderId.Contains(a.OrderId))
.Select(a => a.ApptId);
It seems like this is all you need:
var apptOrders =
model
.getMyData
.Where(x => x.ApptId == apptId)
.Select(y => new { y.OrderId, y.AppointmentsId });
So I have a table like this:
Now I want distinct ShortCode order by the ID descending. In other words, the distinct last records. Like this:
So I tried GroupBy like:
var data = db.ShortCodes.GroupBy(x => x.ShortCode).Select(x => x.FirstOrDefault()).OrderByDescending(s=> s.ID);
This gave me distinct records but not the last ones, nor ordered by ID descending:
Now I also tried like suggested here
var data = db.ShortCodeManager
.GroupBy(s => s. ShortCode)
.Select(g => g.First())
.OrderByDescending(s => s.ID);
This gave me the error The method 'First' can only be used as a final query operation. Consider using the method 'FirstOrDefault' in this instance instead.
So I modified to FirstOrDefault() like:
var data = db.ShortCodeManager
.GroupBy(s => s. ShortCode)
.Select(g => g.FirstOrDefault())
.OrderByDescending(s => s.ID);
This also gave me distinct records but not the last records:
So finally I tried like suggested here:
var data = db.ShortCodeManager.Where(a => a.ID > 0).GroupBy(x => x.ShortCode).OrderByDescending(grp => grp.Max(g => g.ID)).Select(a => a.FirstOrDefault());
Again, this gave me distinct records but not the last ones, nor ordered by ID descending:
So how am I to write the query to get the result I want in Linq? Also note, I need more of the distinct last records than ordering by ID descending. If anyone also knows how to write it in raw SQL it might be useful as well.
This LINQ query should work for your case:
var result = db.ShortCodeManager
.GroupBy(x => x.ShortCode)
.Select(gr => new { Id = gr.Max(g => g.Id), ShortCode = gr.Key})
.ToList();
EDIT:
Based on your comment it looks like you need to cast anonymous object result to ShortCodeManagerModel type and then pass it to your view. So, somethin like this:
var result = db.ShortCodeManager
.GroupBy(x => x.ShortCode)
.Select(gr => new { Id = gr.Max(g => g.Id), ShortCode = gr.Key})
.ToList();
var model = result
.Select(x => new ShortCodeManagerModel { Id = x.Id, ShortCode = x.ShortCode })
.ToList();
And then pass model to you view.
Am trying to refactor some data in order to display some charts.
I can't seem to figure out why using the following, it lists all the values at the top rather than being sequential like the source data.
var categories = VehicleSales.Select(v => v.name).Distinct().ToList();
var refactoredResults = new List<StackedColumnChart>();
foreach (var category in categories)
{
var subresult = VehicleSales.Where(x => x.vehicleType == category)
.GroupBy(x => x.vehicleType)
.Select(gcs => new StackedColumnChart
{
Category = category,
Values = gcs.Select(x => (int)x.data).DefaultIfEmpty(0).ToList()
}).ToList();
refactoredResults.AddRange(subresult);
}
Source Data:
Then the actual results and expected results:
Thanks in advance!
You can do that without loop and selecting a distinct values, just use GroupBy method and map each group to StackedColumnChart using Select
var refactoredResults = VehicleSales
.GroupBy(s => s.Category)
.Select(g => new StackedColumnChart
{
Category = g.Key,
Values = g.Select(s => s.Value).ToList()
})
.ToList();
If the original data is not sorted and you'll need to sort the values by week number, you can use OrderBy clause before selecting a values Values = g.OrderBy(s => s.WeekNumber).Select(s => s.Value).ToList()
I have two tables People and Ordersand a many-to-many relationship between the two using PeopleOrders.
Each order is associated with two people: Client and Salesman.
I have the following query:
var query = db.People
.Where(u => u.Description.Equals("Client"))
.Select(u => new {u.Id, OrderId = u.Orders.Select(p => p.Id))
})
.ToList();
This returns a json like this:
[{"Id":1,"OrderId":[2]},{"Id":9,"OrderId":[10,11,12,13]},{"Id":14,"OrderId":[14,15]}]
The ClientID and an array of orders.
I need to invert. Orders can't be an array.
So I need OrderID associated with the ClientID. Something like this:
[{"OrderId":2,"Id":1},{"OrderId":10,"Id":9},{"OrderId":11,"Id":9},{"OrderId":12,"Id":9},{"OrderId":13,"Id":9}]
The query would be something like:
var query = db.Orders
But I need to subquery the People table, so it return only Client; otherwise, it will return a array of People like:
{"OrderId":2,"Id":[1,10]}
Thank you in advance.
Use SelectMany:
var query = db.People
.Where(u => u.Description.Equals("Client"))
.SelectMany(u => u.Orders.Select(p => new {u.Id, p.OrderId}))
.ToList();
You could try something like this (using SelectMany, in order you flatten the projection of your data):
var query = db.People
.Where(person => person.Description.Equals("Client"))
.Select(person => new
{
PersonOrders = person.Orders
.Select(order => new
{
PersonId = person.Id,
OrderId = order.Id))
})
})
.SelectMany(x=>x.PersonOrders)
.ToList();
I'm trying to select multiple columns not in a group by using linq - c#.
Using linq, I'm trying to group by ISNULL(fieldOne,''),ISNULL(fieldTo,'') and then select field_One, field_Two, field_Three for each group. So for each row that the group by would return, I want to see numerous rows.
So far I have the following, but can't seem to select all the needed columns.
var xy = tableQueryable.Where(
!string.IsNullOrEmpty(cust.field_One)
|| ! string.IsNullOrEmpty(ust.field_Two)
).GroupBy(cust=> new { field_One= cust.field_One ?? string.Empty, field_Tow = cust.field_Two ?? string.Empty}).Where(g=>g.Count()>1).AsQueryable();
Can somebody help pls?
You are pretty much there - all you are missing is a Select from the group:
var xy = tableQueryable
.Where(!string.IsNullOrEmpty(cust.first_name) || ! string.IsNullOrEmpty(ust.lastName))
.GroupBy(cust=> new { first_name = cust.first_name ?? string.Empty, last_name = cust.last_name ?? string.Empty})
.Where(g=>g.Count()>1)
.ToList() // Try to work around the cross-apply issue
.SelectMany(g => g.Select(cust => new {
Id = cust.Id
, cust.FirstName
, cust.LastName
, cust.RepId
}));
Select from each group does the projection of the fields that you want, while SelectMany dumps all the results into a flat list.
Would this work for you?
var groupsWithDuplicates = tableQueryable
.Where(c => !string.IsNullOrWhiteSpace(c.first_name) || !string.IsNullOrWhiteSpace(c.last_name))
.GroupBy(c => new { FirstName = c.first_name ?? "", LastName = c.last_name ?? "" })
.Where(group => group.Count() > 1) // Only keep groups with more than one item
.ToList();
var duplicates = groupsWithDuplicates
.SelectMany(g => g) // Flatten out groups into a single collection
.Select(c => new { c.first_name, c.last_name, c.customer_rep_id });
For me I have used following query to do the filter Customer and get the customer records group by the JobFunction. In my case the issue get resolved after adding the .AsEnumerable() after the where solve the problem.
var query = _context.Customer
.Where(x => x.JobTitle.ToUpper().Contains(searchText.ToUpper())).AsEnumerable()
.GroupBy(item => item.JobFunction,
(key, group) => new {
JobFunction = key,
CustomerRecords = group.ToList().Select(c => c).ToList()
})
.ToList();