I have this sql query that performs a groupby on a single field. It then counts the groupby's. So far so good.
select type, count(*)
from myTable
group by type
//Result
//TypeA = 5
//TypeB = 3
However, I am having trouble performing this query with Linq as I need to map the outcome of Count() to a specific entity.
The entity I want to map the count to:
public class MyEtity(){
public int TypeACount {get; set;}
public int TypeBCount {get; set;}
}
The linq query I currently use which
MyEntity test = data
.GroupBy(c => c.type)
.Select(g => new MyEntity (){
TypeACount = g.Where(d => d.type == "A").Count(),
TypeBCount = g.Where(d => d.type == "B").Count()
});
Extra info
Based on some answers, a little extra info. My original plan was to use following.
var firstResults = session.Query<MyEntity>()
.Where(//several date filter conditions)
.ToList();
return new MyEntity() {
TypeACount = firstResults.Where(s => s.type == "A").Count(),
TypeBCount = firstResults.Where(s => s.type == "B").Count()
};
This works, but table queried is rather large and the query took quite some time. Based on a colleagues feedback I was asked if the query couldn't be made in to 1 part instead of separating it. The idea being that the query counting logic would remain in SQL rather than in C#. I don't know if that would actually be faster, but that is what I am trying to figure out.
You should map after you get the information
var results = data
.Where(c => c.TypeOfUsage == "A" || c.TypeOfUsage == "B")
.GroupBy(c => c.TypeOfUsage)
.Select(g => new
{
Type = g.Key,
Count = g.Count()
}).ToList();
MyEntity test = new MyEntity
{
TypeACount = results.FirstOrDefault(d => d.Type == "A")?.Count ?? 0,
TypeBCount = results.FirstOrDefault(d => d.Type == "B")?.Count ?? 0
}
Or if you don't have C# 6
var a = results.FirstOrDefault(d => d.Type == "A");
var b = results.FirstOrDefault(d => d.Type == "B");
MyEntity test = new MyEntity
{
TypeACount = a == null ? 0 : a.Count,
TypeBCount = b == null ? 0 : b.Count
}
Another option would be to use a constant group by.
MyEntity test= data
.Where(c => c.TypeOfUsage == "A" || c.TypeOfUsage == "B")
.GroupBy(c => 1)
.Select(g => new MyEntity
{
TypeACount = g.Where(d => d.TypeOfUsage == "A").Count(),
TypeBCount = g.Where(d => d.TypeOfUsage == "B").Count()
}).Single();
This would be more like the following SQL
select
sum(case when typeOfUseage = 'A' then 1 else 0 end) AS TypeACount
, sum(case when typeOfUseage = 'B' then 1 else 0 end) AS TypeBCount
from myTable
why not the clasic way?, I do not see in your query the reason for group by or Select;
var entity=new MyEntity()
entity.TypeACount = data.Count(a => a.TypeOfUsage == "A"),
entity.TypeBCount =data.Count(b => b.TypeOfUsage == "B")
Related
I tried to divided Linq queries into 3 (total, success, fail) but so far "Total" Linq query is working fine. Please help me to get "Success", "Fail" columns (it has mulitple statuses and we have to check the last column of each transaction and destination)
Note: you need to group by ProcessTime, TransactionId, Destination and check last column whether it is success or Fail then apply count (we are using oracle as backend)
LINQ for Total count
var query = (from filetrans in context.FILE_TRANSACTION
join route in context.FILE_ROUTE on filetrans.FILE_TRANID equals route.FILE_TRANID
where
filetrans.PROCESS_STRT_TIME >= fromDateFilter && filetrans.PROCESS_STRT_TIME <= toDateFilter
select new { PROCESS_STRT_TIME = DbFunctions.TruncateTime((DateTime)filetrans.PROCESS_STRT_TIME), filetrans.FILE_TRANID, route.DESTINATION }).
GroupBy(p => new { p.PROCESS_STRT_TIME, p.FILE_TRANID, p.DESTINATION });
var result = query.GroupBy(x => x.Key.PROCESS_STRT_TIME).Select(x => new { x.Key, Count = x.Count() }).ToDictionary(a => a.Key, a => a.Count);
Check this solution. If it gives wrong result, then I need more details.
var fileTransQuery =
from filetrans in context.AFRS_FILE_TRANSACTION
where accountIds.Contains(filetrans.ACNT_ID) &&
filetrans.PROCESS_STRT_TIME >= fromDateFilter && filetrans.PROCESS_STRT_TIME <= toDateFilter
select filetrans;
var routesQuery =
from filetrans in fileTransQuery
join route in context.AFRS_FILE_ROUTE on filetrans.FILE_TRANID equals route.FILE_TRANID
select route;
var lastRouteQuery =
from d in routesQuery.GroupBy(route => new { route.FILE_TRANID, route.DESTINATION })
.Select(g => new
{
g.Key.FILE_TRANID,
g.Key.DESTINATION,
ROUTE_ID = g.Max(x => x.ROUTE_ID)
})
from route in routesQuery
.Where(route => d.FILE_TRANID == route.FILE_TRANID && d.DESTINATION == route.DESTINATION && d.ROUTE_ID == route.ROUTE_ID)
select route;
var recordsQuery =
from filetrans in fileTransQuery
join route in lastRouteQuery on filetrans.FILE_TRANID equals route.FILE_TRANID
select new { filetrans.PROCESS_STRT_TIME, route.CRNT_ROUTE_FILE_STATUS_ID };
var result = recordsQuery
.GroupBy(p => DbFunctions.TruncateTime((DateTime)p.PROCESS_STRT_TIME))
.Select(g => new TrendData
{
TotalCount = g.Sum(x => x.CRNT_ROUTE_FILE_STATUS_ID != 7 && x.CRNT_ROUTE_FILE_STATUS_ID != 8 ? 1 : 0)
SucccessCount = g.Sum(x => x.CRNT_ROUTE_FILE_STATUS_ID == 7 ? 1 : 0),
FailCount = g.Sum(x => failureStatus.Contains(x.CRNT_ROUTE_FILE_STATUS_ID) ? 1 : 0),
Date = g.Min(x => x.PROCESS_STRT_TIME)
})
.OrderBy(x => x.Date)
.ToList();
When I run the following Linq:
var selectedProduct = db.Products.FirstOrDefault(a => a.ProductNr == productNr)?.Id;
model.PackTypes = db.Zones
.Where(az => az.ProductId == selectedProduct && az.StoragePrio > 0)
.ToList()
.DistinctBy(p => p.PackType)
.OrderBy(x => x.PackType)
.Select(x => new DropdownItemViewModel<int>
{
Id = (int)x.PackType,
Name = x.PackType.Translate()
});
return true;
I get this error:
System.InvalidOperationException: 'Nullable object must have a value.' on this code Id = (int)x.PackType,
Now I know I must do a nullcheck so I have tried this:
if (x.PackType != null)
return new DropdownItemViewModel<int>
{
Id = (int)x.PackType,
Name = x.PackType.Translate()
};
return null;
Still doesn't work, by that I mean I still have problem with NullCheck.
This query more effective and should not have all mentioned errors:
var query =
from p in db.Products
where p.ProductNr == productNr
join az in db.Zones on p.Id equals az.ProductId
where az.StoragePrio > 0 && az.PackType != null
select new { az.PackType };
model.PackTypes = query
.Distinct()
.OrderBy(x => x.PackType)
.Select(x => new DropdownItemViewModel<int>
{
Id = (int)x.PackType,
Name = x.PackType.Translate()
})
.ToList();
Instead of two database requests this query sends only one. Also all operations are done on the server side.
I have the following class:
public class Article
{
long Id;
List<Category> Categories;
}
I am using EF Core 5 and What I need is a LINQ query against SQLite that returns all the articles that have all the categories that I specify.
I tried the following code:
List<long> cIds = c.Select (x => x.Id).ToList ();
query.Where (art => cIds.All (cId => art.Categories.Select (c => c.Id).Contains (cId)));
but the compiler says
InvalidOperationException: The LINQ expression 'DbSet<Article>()
.Where(a => __cIds_0
.All(cId => DbSet<Dictionary<string, object>>("ArticleCategory")
.Where(a0 => EF.Property<Nullable<long>>(a, "Id") != null && object.Equals(
objA: (object)EF.Property<Nullable<long>>(a, "Id"),
objB: (object)EF.Property<Nullable<long>>(a0, "ArticlesId")))
.Join(
inner: DbSet<Category>(),
outerKeySelector: a0 => EF.Property<Nullable<long>>(a0, "CategoriesId"),
innerKeySelector: c => EF.Property<Nullable<long>>(c, "Id"),
resultSelector: (a0, c) => new TransparentIdentifier<Dictionary<string, object>, Category>(
Outer = a0,
Inner = c
))
.Select(ti => ti.Inner.Id)
.Any(p => p == cId)))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.
How can I obtain it?
A possible workaround I found is the following:
List<long> cIds = c.Select (x => x.Id).ToList ();
query = query.Where (art => art.Categories.Select (c => c.Id).Any (x => cIds.Contains (x)));
query = query.Include (x => x.Categories);
result = await query.ToListAsync ();
result = result.Where (art => cIds.All (cId => art.Categories.Select (c => c.Id).Contains (cId))).ToList ();
But I was wondering if I could obtain the same result with a single LINQ query.
Thanks in advance
UPDATE:
I'll just add the function where this code will be used and make make an example to make things clearer:
This is the function where the code will be used:
public async Task<List<Article>> SearchAsync (string search, Section s, Website w,
List<Category> c)
{
List<Article> result = new List<Article> ();
if (
search == ""
&& s == null
&& w == null
&& c.Count == 0
)
return result;
IQueryable<Article> query = dbSet.AsQueryable ();
if (search != "")
query = query.Where (x => x.Title.Contains (search) || x.Summary.Contains (search));
if (s != null)
query = query.Where (x => x.SectionId == s.Id);
if (w != null)
query = query.Where (x => x.WebsiteId == w.Id);
if (c.Count > 0)
{
List<long> cIds = c.Select (x => x.Id).ToList ();
query = query.Where (art => art.Categories.Select (c => c.Id).Any (x => cIds.Contains (x)));
}
query = query.Include (x => x.Categories);
result = await query.ToListAsync ();
if (c.Count > 0)
{
List<long> cIds = c.Select (x => x.Id).ToList ();
result = result.Where (art => cIds.All (cId => art.Categories.Select (c => c.Id).Contains (cId))).ToList ();
}
return result;
}
And here is an example:
Let's say c will contain ids 9,10,11 and the articles collection is the following pseudo code:
List<article> articles = new List<Article> ()
{
new Article () {Id = 1, Categories = "12,44,55"}
new Article () {Id = 2, Categories = "7,8,9,10,11"}
new Article () {Id = 3, Categories = "9,10,11"}
}
The linq query should return Article with Id 2 and 3 because both contains all of the ids present in c.
One of the solutions using Intersect, but we have to prepare data for intersection.
// articles query
var query = ...
var cIds = c.Select(x => x.Id).ToList();
var idsCount = cIds.Count();
// translating list of IDs to IQueryable
var categoryIdsQuery = dbContext.Categories
.Where(c => cIds.Contains(c.Id))
.Select(c => c.Id);
query = query
.Where(art => art.Categories
.Select(c => c.Id)
.Intersect(categoryIdsQuery)
.Count() == idsCount
)
.Include(x => x.Categories);
What I need is a LINQ query against SQLite that returns all the articles that have all the categories that I specify.
So you have a sequence of Category Ids and you want all Articles, each Article with only the Categories that are in your sequence of Category Ids.
I'm not sure what your variable 'c' is, but it seems to me that the following statement returns the Ids of all c:
List<long> cIds = c.Select (x => x.Id).ToList ();
If c is your sequence of Categories, then you will have the Ids of all existing categories. This will mean that you will have all Articles, each with all Categories.
If you have a local sequence of Category Ids, with a limited count (say about 250), then you should use Contains:
IEnumerable<long> categoryIds = ...
var articlesWithTheseCategories = dbContext.Articles.Select(article => new
{
Id = article.Id,
Categories = article.Categories
.Where(category => categoryIds.Contains(category.Id)
.ToList(),
})
So if you have CategoryIds 2, 3, and 12, this query will give you all Articles with only the Categories with ids 2, 3, 12.
If Article 40 has only Categories 20, 21, 21, then Article 40 will be in your result, but it will have an empty Categories list.
If you don't have your Category Ids locally, but you have a predicate to select the Category Ids, then your query will be like:
IQueryable<long> categoryIds = dbContext.Categories
.Where(category => category.Status == StatusCode.Obsolete); // predicate
var articlesWithTheseCategories = dbContext.Articles.Select(article => new
{
Id = article.Id,
Categories = article.Categories
.Where(category => categoryIds.Contains(category.Id)
.ToList(),
});
Because your first query is an IQueryable<...> it is not executed yet. If you want you can make it one big statement:
var articlesWithTheseCategories = dbContext.Articles.Select(article => new
{
Id = article.Id,
Categories = article.Categories
.Where(category => dbContext.Categories
.Where(category => category.Status == StatusCode.Obsolete)
.Contains(category.Id))
.ToList(),
});
Although this will not improve efficiency, it surely deteriorates readability.
I am working on a LINQ query which includes some pivot data as below
var q = data.GroupBy(x => new
{
x.Med.Name,
x.Med.GenericName,
}).ToList().Select(g =>
new SummaryDto
{
Name= g.Key.Name,
GenericName = g.Key.GenericName,
Data2012 = g.Where(z => z.ProcessDate.Year == 2012).Count(),
Data2013 = g.Where(z => z.ProcessDate.Year == 2013).Count(),
Data2014 = g.Where(z => z.ProcessDate.Year == 2014).Count(),
Data2015 = g.Where(z => z.ProcessDate.Year == 2015).Count(),
Data2016 = g.Where(z => z.ProcessDate.Year == 2016).Count(),
Data2017 = g.Where(z => z.ProcessDate.Year == 2017).Count(),
TotalCount = g.Count(),
}).AsQueryable();
return q;
The above LINQ takes too long as it queries grp q.Count()*6 times. If there are 10000 records, then it queries 60000 times
Is there a better way to make this faster?
Add year to the group key, then group again, and harvest per-group counts:
return data.GroupBy(x => new {
x.Med.Name
, x.Med.GenericName
, x.ProcessDate.Year
}).Select(g => new {
g.Key.Name
, g.Key.GenericName
, g.Key.Year
, Count = g.Count()
}).GroupBy(g => new {
g.Name
, g.GenericName
}).Select(g => new SummaryDto {
Name = g.Key.Name
, GenericName = g.Key.GenericName
, Data2012 = g.SingleOrDefault(x => x.Year == 2012)?.Count ?? 0
, Data2013 = g.SingleOrDefault(x => x.Year == 2013)?.Count ?? 0
, Data2014 = g.SingleOrDefault(x => x.Year == 2014)?.Count ?? 0
, Data2015 = g.SingleOrDefault(x => x.Year == 2015)?.Count ?? 0
, Data2016 = g.SingleOrDefault(x => x.Year == 2016)?.Count ?? 0
, Data2017 = g.SingleOrDefault(x => x.Year == 2017)?.Count ?? 0
, TotalCount = g.Sum(x => x.Count)
}).AsQueryable();
Note: This approach is problematic, because year is hard-coded in the SummaryDto class. You would be better off passing your DTO constructor an IDictionary<int,int> with counts for each year. If you make this change, the final Select(...) would look like this:
.Select(g => new SummaryDto {
Name = g.Key.Name
, GenericName = g.Key.GenericName
, TotalCount = g.Sum(x => x.Count)
, DataByYear = g.ToDictionary(i => i.Year, i => i.Count)
}).AsQueryable();
I suggest grouping inside the group by year and then converting to a dictionary to access the counts. Whether it is faster to group with year first and then count in-memory depends on the distribution of the initial grouping, but with the database it may depend on how efficiently it can group by year, so I would test to determine which seems fastest.
In any case grouping by year after the initial grouping is about 33% faster than your query in-memory, but again it is vastly dependent on the distribution. As the number of initial groups increase, the grouping by Year queries slow down to match the original query. Note that the original query without any year counts is about 1/3 the time.
Here is grouping after the database grouping:
var q = data.GroupBy(x => new {
x.Med.Name,
x.Med.GenericName,
}).ToList().Select(g => {
var gg = g.GroupBy(d => d.ProcessDate.Year).ToDictionary(d => d.Key, d => d.Count());
return new SummaryDto {
Name = g.Key.Name,
GenericName = g.Key.GenericName,
Data2012 = gg.GetValueOrDefault(2012),
Data2013 = gg.GetValueOrDefault(2013),
Data2014 = gg.GetValueOrDefault(2014),
Data2015 = gg.GetValueOrDefault(2015),
Data2016 = gg.GetValueOrDefault(2016),
Data2017 = gg.GetValueOrDefault(2017),
TotalCount = g.Count(),
};
}).AsQueryable();
Using Entity Framework C# and have this query, I need the part where it says:
where x.Login_Status == "Submitted"
to be dynamic. There are different cases it could be "Submitted" or null or something else and instead of writing multiple if statement with different queries in it, want to have a Predicate in a where clause.
status = (from x in ctx.table
where x.Login_Status == "Submitted"
orderby x.SUB_DATE descending
select new Model_Table()
{
Id = x.ID,
Name = x.NAME,
Code = x.Code,
DateSubmitted = x.SUB_DATE
}).ToList<Model_Table>();
Is that possible?
Solution:
Inside the if statement when more parameters encountered use this
where_expression = x => x.Login_Status == "Submitted" || x.Login_Status == null;
Here is a complete code that worked for me, anything between square brackets replace to suit your code:
Expression<Func<[Replace with your Entity], bool>> where_submitted = x => x.Login_Status == "Submitted";
// Check if all selected
if (CheckBox_Show_All_Submitted.Checked)
{
where_submitted = x => x.Login_Status == "Submitted" || x.Login_Status == null;
}
status =
ctx.[Replace with your Entity Table]
.Where(where_submitted)
.OrderByDescending(x => x.SUB_DATE)
.Select(x => new Model_Table
{
Id = x.ID,
Name = x.NAME,
Code = x.Code,
DateSubmitted = x.SUB_DATE
}).ToList<Model_Table>();
You need an Expression<Func<Entity,bool>>, not a Predicate<Entity>. The difference is that a predicate is a compiled delegate, and an expression is code as data and thus can be translated to SQL.
Here is an example:
//You can have this expression have different values based on your logic
Expression<Func<Entity,bool>> where_expression = x => x.Login_Status == "Submitted";
var query =
ctx.Table
.Where(where_expression)
.OrderByDescending(x => x.SUB_DATE)
.Select(x => new Model_Table())
{
Id = x.ID,
Name = x.NAME,
Code = x.Code,
DateSubmitted = x.SUB_DATE
}).ToList();
Please note that you need to replace Entity with the name of the real class.
Create an extension method for IQueryable like this:
public static class MethodExtensions{
public static IEnumerable<Model_Table> Query(this IQueryable<TEntity> source, string data){
return (from x in source
where x.Login_Status == data
orderby x.SUB_DATE descending
select new Model_Table()
{
Id = x.ID,
Name = x.NAME,
Code = x.Code,
DateSubmitted = x.SUB_DATE
}).ToList<Model_Table>();
}
}
Now you can use it like this:
var result = ctx.table.Query("somethingelse");