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SQL Unions with table counts using EntityFramework LINQ query

I am trying replicate the SQL below using LINQ and Entity Framework and cannot figure out how this should be written.
My simplistic LINQ version does a query per table
public IActionResult Index()
{
dynamic view = new ExpandoObject();
view.AppUsers = Context.AppUsers.Count();
view.CustomerShops = Context.CustomerShops.Count();
view.FavouriteOrders = Context.FavouriteOrders.Count();
view.Items = Context.Items.Count();
view.ItemVariations = Context.ItemVariations.Count();
view.MenuCategories = Context.MenuCategories.Count();
view.MenuCategoryProducts = Context.MenuCategoryProducts.Count();
view.Orders = Context.Orders.Count();
view.Products = Context.Products.Count();
view.ProductVariations = Context.ProductVariations.Count();
view.Shops = Context.Shops.Count();
view.Staffs = Context.Staffs.Count();
return View(view);
}
I use this pattern from time to time to for reporting on my column counts and thought this should be easy to do in LINQ, but no luck so far.
This pure SQL UNION would only generate 1 SQL request, instead of a request per table.
select * from (
select 'asp_net_roles' as type, count(*) from asp_net_roles
union
select 'asp_net_user_roles' as type, count(*) from asp_net_user_roles
union
select 'asp_net_users' as type, count(*) from asp_net_users
union
select 'app_users' as type, count(*) from app_users
union
select 'shops' as type, count(*) from shops
union
select 'staffs' as type, count(*) from shops
union
select 'items' as type, count(*) from items
union
select 'item_variations' as type, count(*) from item_variations
union
select 'products' as type, count(*) from products
union
select 'product_variations' as type, count(*) from product_variations
union
select 'menu_categories' as type, count(*) from menu_categories
) as counters
order by 1;
I saw a partial implementation [linq-group-by-multiple-tables] (https://stackoverflow.com/a/3435503/473923) but this is based of grouping data.
FYI: I'm new to C#/Linq, so sorry if this seams obvious.

Use the this code from my answer
And fill ExpandoObject with result:
var tablesinfo = Context.GetTablesInfo();
var expando = new ExpandoObject();
if (tablesinfo != null)
{
var dic = (IDictionary<string, object>)expando;
foreach(var info in tablesinfo)
{
dic.Add(info.TableName, info.RecordCount);
}
}
Idea is that you can UNION counts if you group entities by constant.
Schematically function builds the following IQueryable Expression:
var tablesinfo =
Context.AppUsers.GroupBy(x => 1).Select(g => new TableInfo{ TableName = "asp_net_roles", RecordCount = g.Count() })
.Concat(Context.MenuCategories.GroupBy(x => 1).Select(g => new TableInfo{ TableName = "menu_categories", RecordCount = g.Count() }))
.Concat(Context.Items.GroupBy(x => 1).Select(g => new TableInfo{ TableName = "items", RecordCount = g.Count() }))
....

There is nothing wrong with your LINQ query. It's very acceptable approach. However it's not the most efficient.
There is no need to fetch count from individual tables one by one. You can get the counts from all the tables at once using the System tables Sys.Objects and Sys.Partitions. Just try running this query in your database.
SELECT A.Name AS TableName, SUM(B.rows) AS RecordCount
FROM sys.objects A INNER JOIN sys.partitions B
ON A.object_id = B.object_id
WHERE A.type = 'U' AND B.index_id IN (0, 1)
GROUP BY A.Name
For quick response and cleaner code, you can store this SQL query in a string variable, and run the LINQ
var result = dataContext.ExecuteQuery<YOUR_MODEL_CLASS>
(your_string_query);

I would put something like this:
Dictionary<string, int> view = new() {
new() {'asp_net_roles', Context.AppUsers.Count() },
...
}
return View(view);
maybe not the most pure way, but does the job (unless I misunderstood what you try to accomplish)

How to get total available rows from paginated ef core query

Thanks in advance for taking time to read this question.
I have a view in my database, lets call it Members_VW
In my .net 5 API, I'm trying to get a paginated response for the list of members from the view with search parameters. I need to also return the total number of responses for the front end to know in how many pages the results will be returned in.
Currently the Members_VW is made with a query like:
select
col1, col2, col3
from
table1 1
inner join table2 2 on 1.key = 2.key
inner join tble3 3 on 3.key = 2.key
where
defaultcondition1 = '1'
and
defaultcondition2 = '2'
I referred to this answer and tried using CTE which ended up changing my view to using a query like this:
with cte1 as (
select
col1, col2, col3
from
table1 1
inner join table2 2 on 1.key = 2.key
inner join tble3 3 on 3.key = 2.key
where
defaultcondition1 = '1'
and
defaultcondition2 = '2')
cte2 as (
select count(*) over() from cte1 )
select
*
from
cte1, cte2
But this didn't work because it would always return the total number of rows in cte1 without any of the filters applied.
So, I continued to try to construct queries to return the total number of rows after the conditions are applied and found that this query works:
select
col1, col2, col3, count(*) over()
from
table1 1
inner join table2 2 on 1.key = 2.key
inner join tble3 3 on 3.key = 2.key
where
defaultcondition1 = '1'
and
defaultcondition2 = '2'
Currently, I'm trying to implement the same query with EF Core but am struggling to implement that.
I've tried implementing the solution provided here, but as one of the comments suggests, this implementation is no longer allowed.
I am trying to avoid an implementation where I use a raw query. Is there anyway to get the result from count(*) over() without using a raw query?
The following is my current implementation:
IQueryable<MembersVW> membersQuery = _context.MembersVW;
membersQuery = membersQuery.Where(u => u.MemberId == memberid);
membersQuery = membersQuery.OrderBy(m => m.MemberId).Skip(page * size).Take(size);
When I do:
membersQuery = membersQuery.Count()
I'm returned with the following error:
Error CS0029 Cannot implicitly convert type 'int' to 'System.Linq.IQueryable<PersonalPolicyAPI.Models.VwPersonalPolicyMember>'
Again, thanks for reading my question, appreciate any help you can offer. 🙏🏾

I've read your question about can it be done with one query. While I'm not aware of any way to do it with 1 query I can offer one more solution that will help with your concern about performance and 2 queries. I do this frequently. 😁 Try:
//execute both queries at the same time instead of sequentially
var countqry = membersQuery.CountAsync();
var pageqry = membersQuery.OrderBy(m => m.MemberId).Skip(page * size).Take(size).ToListAsync();
//wait for them both to complete
Task.WaitAll(countqry, pageqry);
//use the results
var count = countqry.Result;
var page = pageqry.Result;

membersQuery.Count() returns integer not the queryable
you can do
int count = membersQuery.Count();
List<MemberVW> = membersQuery.OrderBy(m => m.MemberId).Skip(page * size).Take(size).ToList();
and you can return with
public class MemberVwWithCount {
public int Count{get;set;}
public List<MemberVW> Members {get; set;}
}

You try to assign the Count Value, which is an Integer, to the variable of your query, which is an IQueryable. That's all there is to it.
If you want to do it in one single query, as you suggest in one of your comments, you can first execute the query to get all Entries, then count the result, and then filter the result with skip/take. This is most probably not the most efficient way to do this, but it should work.
I'd also suggest to use AsNoTracking() if you do not modify any data in this function/api.
EDIT:
I'd suggest this solution for now. The counting is fast, as it actually doesn't fetch any data and just counts the rows. It is still two queries tho, gonna try to combine it & edit my answer later.
var count = await yourContext.YourTable.CountAsync();
var data = await yourContext.YourTable
.OrderBy(x => x.YourProp)
.Skip(10).Take(10)
//.AsNoTracking()
.ToListAsync();
EDIT2:
Okay, so, I couldn't get it to just make on DB-Call yet, however, I could combine it syntactically. However, the approach in my first edit is easier to read and does basically the same. Still, gonna dig deeper into this, there's gotta be a funky way to do this.
var query = yourContext.YourTable.AsQueryable();
var result = await query.OrderBy(x => x.Prop)
.Select(x => new {Data = x, Count = query.Count()} )
.Skip(50).Take(50)
.AsNoTracking()
.ToListAsync();
var count = result.FirstOrDefault()?.Count ?? 0; //If empty/null return 0
var data = result.Select(x => x.Data).ToList();

In membersQuery = membersQuery.Count() line you are assigning integer value to a queryable list, which is incorrect. You can get the list item counts after your query like this i.e.
membersQuery = membersQuery.OrderBy(m => m.MemberId).Skip(page * size).Take(size);
int totalCount = membersQuery.Count();
To get count column in same list, you first need to add Count property in your MembersVW class and then use LINQ projection to add column value.
Solution-1:
memberQuery = membersQuery.Select(p => new MembersVW
{
col1 = p.col1
col2 = p.col2
col3 = p.col3
count = totalCount
});
Solution-2:
With LINQ foreach loop i.e.
membersQuery.ForEach(item =>
{
item.count = totalCount;
});

Is there any way to make this query faster and build where clause outside of loop?

I have the following code, (and I am completely aware about parameterized queries and SQL Injection):
foreach(var item in items)
{
string query = "select sum(convert(decimal(18,3),tbl.Price)) p, sum(convert(decimal(18,2),tbl.Sale)) s from table1 tbl " +
$"where tbl.ID = {item .ID}";
Execute(query);
//Do stuff with query result
}
The problem is I have a lot of items and I have to execute the query for each of the items because the where clause will be complete in each step. I think if I will be able to make my query out side of my loop, my query will be faster. But I don't know how. Is there any way to do this?

Instead of executing the query for every item. You can add group by to your query and execute only once.
string query = "select tbl.ID, sum(convert(decimal(18,3),tbl.Price)) p, sum(convert(decimal(18,2),tbl.Sale)) s from table1 tbl group by tbl.ID ";
var result = Execute(query);
foreach(var item in items)
{
var row = result.Select(r => r.ID == item.ID).FirstOrDefault();
//Do stuff with query result
}

Do not execute the query for each ID separately. Instead, execute a single query for all Ids using group by to get the p and s values for each id and a parameterized in clause (or better yet, a stored procedure with a table valued parameter).
Here is the IN version of the query:
select Id,
sum(convert(decimal(18,3),tbl.Price)) p,
sum(convert(decimal(18,2),tbl.Sale)) s
from table1 tbl
Where Id IN(<1,2,3,4....>)
group by Id
Replace <1,2,3,4....> with parameters like described in this answer.
Here is the table valued parameter version of the query:
select tbl.Id,
sum(convert(decimal(18,3),tbl.Price)) p,
sum(convert(decimal(18,2),tbl.Sale)) s
from table1 tbl
inner join #items i on tbl.Id = i.Id
group by tbl.Id
For a detailed explanation about using table valued parameters, read this answer.

How to select Distinct names from a xml database using LINQ?

i am trying this query to get all the city's
var queryAllCustomers = from cust in loadedCustomData.Descendants("record")
select (string)cust.Element("City") ;
so it returns all city's including repeated, but i only want to get distinct city i.e to repeat only ones so how to achieve that?

Use Distinct Extension Method
var queryAllCustomers = (from cust in loadedCustomData.Descendants("record")
select (string)cust.Element("City")).Distinct();

LinqToSql - Prevent sub queries when limiting number of rows returned

Dim query = (From p in Parent _
select _
p.ID, _
Tags = String.Join("|", p.Child.Select(Function(c) c.Tag.TagName).ToArray)).Take(100)
In the above query, when using Take to limit the rows returned, a separate SQL query is executed for each row to return the 'Tags' field. If I remove Take(100), a single query to sent to Sql Server.
So, how do I limit the number of rows returned, while preventing a new sub query being executed for each row?

edit2
When working with nested types, so doing new { r, r.childrenCollection }, LINQ translates this to (SELECT TOP 100 FROM r), deleting the join information. When doing a join by yourself this doesn't happen. So something like:
var thingyWithChilds
= (from p in dc.RightCategories
join r in dc.Rights on p.Id equals r.CategoryId
select new { p.Id, r });
var bla = thingyWithChilds.Take(100);
will not cause the same problem.
other stuff that might apply
You're doing ToArray() which causes the query to execute as it isn't a IQueryable. Just do ToArray() after you do Take().
edit According to this SO topic: Is there a LINQ equivalent of string.Join(string, string[]), it is neither possible to use String.Join if you want to do everything on the server, as there is no SQL command available to do that in TSQL.