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Column getting lost in LINQ with Method Syntax after group by

I'm pretty new to LINQ and trying to figure it out. I have the following statement:
Context.dataset1
.Join(
Context.dataset2,
r => r.ID, o => o.ID,
(r, o) => new { PartID = r.PartID, Quantity = r.Quantity1 - r.Quantity2, Date = o.Date })
.GroupBy(
column => new { column.Date },
(key, group) => new {Date = key.Date, Quantity = group.Sum(g => g.Quantity) })
.Where(x => x.Quantity > 0);
the return data set looks like this
| Date | Quantity |
| ------------- | ---------|
| 2022-01-01 | 333 |
| 2022-01-02 | 444 |
| 2022-03-03 | 444 |
what i want it to look like is
| PartID | Date | Quantity |
|--------| ------------- | ---------|
|1 | 2022-01-01 | 333 |
|1 | 2022-01-02 | 444 |
|2 | 2022-03-03 | 444 |
Basically it seems that when I do the groupby I lose access to the PartId column since i'm no specifying it inside the groupby. I'm not sure how to make it appear without grouping by it which I don't want to do.
Any help would be great. Thanks.

What if two different part ids exist for the same date? What part id would it show? If you really want the part id, then you need to include the part id in your group by. For example:
column => new { column.PartID, column.Date }
This will mean that if you have multiple part ids for the same date, you will have as many rows for that date as you have distinct part ids. Based on your comments, this seems like what you're after.

Filter LINQ To Entities (EF Core) query by List of HashSet of String and Enum

I have this Linq to Entities (EF Core) query which looks like below
var query = (from p in db.Samples
join q in db.Items on p.Id equals q.SampleId
Where p.active = IsActive and p.Id = GivenId
group new
{
p.Name,
p.Address,
p.Marks,
p.LocationId,
q.EmailId,
q.Grade
}
by new
{ q.Grade }
into data
select new DataSummary()
{
UserName = data.Name,
Grade = data.Min(x => x.Grade),
Email = data.Min(x => x.Email,
Total = data.Sum(x => x.Marks)
}.ToList()
Now I have a constant List of Hashset of Grades and Location that looks like this:
public List<(HashSet<string> Grades, HashSet<Location> Loctions)> LocationGrades => new()
{
(new() { "A", "B" }, new()), // Includes all location
(new() { "C"}, new(){
Location.Boston, //Location is Enum
Location.Maine
}
}
I want to get the data where if the student has grade A or B include all location and if the student has grade C only include Boston and Maine.
Is it possible to integrate this within the LINQ to Entities query?
Sample Table
| ID | Name | Address | Marks | LocationId |
|-----|-------|---------|-------|-------------|
| 234 | Test | 123 St | 240 | 3 (Maine) |
| 122 | Test1 | 234 St | 300 | 5 (Texas) |
| 142 | Test1 | 234 St | 390 | 1 (Boston) |
Items Table
| ID | SampelId | Grade | Email |
|----|----------|-------|-------|
| 12 | 234 | A | a.com |
| 13 | 122 | C | b.com |
| 14 | 142 | C | c.com |
So, In the table above I shouldn't get Texas row but get Boston row as they both have Grade C but Texas does not exist in the HashSet combo.

Okay, now I got it. You have to add dynamic ORed constraints to the query based on a given list of elements. This is a little tricky, because AND can be done with using multiple .Where() statements, but OR not. I did something similar recently against CosmosDB by using LinqKit and the same should also work against EF.
In your case you probably of to do something like this:
...
into data
.WhereAny(grades, (item, grade) => item.Grade == grade)
select new DataSummary()
...
I think the given example doesn't match your exact case, but it allows you to define multiple ORed constraints from a given list and I think this is the missing part you're searching. Take care to use within the lambda method only definitions which are also supported by EF core. The given inner enumeration (in this example grades) will be iterated on the client side and can be dynamically build with everything available in C#.

Comparison with multiple Where clause in LINQ C#

I have two DataTables:
DataTable dtCatalogFromMySql;
DataTable dtDataForExistingProducts;
dtCatalogFromMySql
Id | productname | barcode | pricesell| type
---+--------------+----------+----------+------
1 | Abz | 123 | 2.01 | RS // different product name
2 | Abd | 122 | 8.90 | RS // different price
3 | Abx | 125 | 21.00 | WS // both different
4 | Abf | 124 | 2.11 | RS
5 | Abg | 126 | 8.01 | WS
6 | Abh | 127 | 60.23 | RS
7 | Abi | 128 | 9.10 | RS
dtDataForExistingProducts
Id | productname | barcode | pricesell| type
---+--------------+----------+----------+------
1 | Abc | 123 | 2.01 | RS
2 | Abd | 122 | 3.90 | RS
3 | Abe | 125 | 23.00 | WS
4 | Abf | 124 | 2.11 | RS
5 | Abg | 126 | 8.01 | WS
6 | Abh | 127 | 60.23 | RS
7 | Abi | 128 | 9.10 | RS
I need return only rows which are different as in first table
I need select all data where Prod_No equals to baracode and Descript not equals to productname and Retail_PRC also not equals to pricesell.
I am not getting results with this code
List<DataRow> matchingRows = dtCatalogFromMySql.AsEnumerable()
.Where(a => dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<string>("Prod_No"))
.Contains(a.Field<string>("barcode")))
.Where(a => !dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<string>("Descript"))
.Equals(a.Field<string>("productname")))
.Where(a => !dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<decimal>("Retail_PRC"))
.Equals(Convert.ToDecimal(a.Field<double>("pricesell"))))
.ToList();
I suppose, Contains() will also fetch the data if barcode = 123456 and Prod_No = 1234, it is right? If I am right what is right way to compare string exactly same

You may want to consider a clearer syntax such as:
var results = from t1 in dtCatalogFromMySql.AsEnumerable()
join t2 in dtDataForExistingProducts.AsEnumerable() on
(string)t1["barcode"] equals (string)t2["Prod_No"]
where (string)t1["productname"] != (string)t2["descript"] &&
Convert.ToDecimal((double)t1["pricesell"]) !=
(decimal)t2["Retail_PRC"]
select t2;
The Join is definitely the way to go. You can modify the select according to your required result set.
trighati makes a good point about using OR instead of AND. This is assuming that you want all of the data where at least one of your values changed where Prod_no and barcode are equal. This would change the query to be:
var results = from t1 in dtCatalogFromMySql.AsEnumerable()
join t2 in dtDataForExistingProducts.AsEnumerable() on
(string)t1["barcode"] equals (string)t2["Prod_No"]
where (string)t1["productname"] != (string)t2["descript"] ||
Convert.ToDecimal((double)t1["pricesell"]) !=
(decimal)t2["Retail_PRC"]
select t2;

Use Join to combine them into one result set, then filter the result set:
var combined = dtDataForExistingProducts.AsEnumerable()
.Join(dtCatalogFromMySql.AsEnumerable(),
ep => ep.Field<string>("Prod_No")
ce => ce.Field<string>("barcode"),
(ep, ce) => new {ExistingProduct = ep, CatalogEntry = ce})
.Where(m => !m.ExistingProduct.Field("Descript")
.Equals(m.CatalogEntry.Field("productname")))
.Where(m => decimal.Parse(m.ExistingProduct.Field("Retail_PRC").ToString())
!= decimal.Parse(m.CatalogEntry.Field("pricesell").ToString()))
.ToList()
;

How to sort a List<String> using data from a column in a ListView

In my application, there is a ListView that contains the Location name and the Picking Priority (Lowest is chosen first) of all the locations that products are kept in. As well as this, I am also creating temporary List's that contain only the locations an individual product is stored in. For example:-
LISTVIEW List<String>
-------- ------------
__________________________ __________________________
|Location |Picking Priority| | Location |
|---------|----------------| |--------------------------|
| A | 100 | | A |
| B | 50 | | C |
| C | 500 | | D |
| D | 150 | |__________________________|
|_________|________________|
What I want to happen is the List to be ordered based on the Picking Priority of that location in the ListView, lowest to highest.
In effect, this would mean the List above would now look like this:-
__________________________
| Location |
|--------------------------|
| A |
| D |
| C |
|__________________________|
How would this be possible to do?

You can order the items based on the listitems, it's ugly, it's slow (slower than using a class with both properties) but it can work.
I assume ListViewItem.Text contains the name of the location and ListViewItem.Subitems[1].Text is the column with the priority (in integer format):
var items = theListView.Items.Cast<ListViewItem>();
var sortedList = theStringList.OrderBy(d => items.Where(i => i.Text == d).Select(i => int.Parse(i.Subitems[1].Text)).First()).ToList();

LINQ grouping by nullable child and parent

everyone!
I've just faced a problem with timing out in my LINQ query.
I have 3 tables: Work, Projects and Subprojects.
Projects:
+--------+
| Id |<--+<--+
| Name | | |
+--------+ | |
SubProjects: | |
+--------+ | |
+->| Id | | |
| | Name | | |
| | ProjId |---+ |
| +--------+ |
| Work: |
| +------------+ |
| | Id | |
| | Type | |
| | ProjId |---+
+--| SubProjId | (nullable)
+------------+
I need to create a report based on Subprojects:
Group by subproject Id,
if subproject Id is null -> group by project Id
I've solved it by making two queries and then merging them, but when sometimes it times out.
I was doing it with
result1.AddRange(result2);
because
var temp = result1.Concat(result2);
is throwing an Exception:
Internal .NET Framework Data Provider error 1004, 0, Unresolvable Var used in Command: VarType=Computed, Id=2090.
Can somebody help me with creating it in one query?

I'm not sure what your code looks like so this might not be perfect but you could try something like this:
var result = from work in works
group work by work.SubProjId ?? work.ProjId into groupedWorks
select groupedWorks.ToList();
or
var result = works.GroupBy(work => work.SubProjId ?? work.ProjId).ToList();

try this query
var itemlist =contex.Work.where(x=>x.SubProjId !=null).Groupby(x=>x.SubProjId).Concat(Contex.Work.where(x=>x.SubProjId ==null).Groupby(x=>x.ProjId)).ToList();

I'm guessing this is what you need:
var groups = from work in ctx.Works // the work table
group work // we want to group whole work "rows"
// we are grouping by project id and subproject id
by new { ProjId = work.ProjId, SubProjId = work.SubProjId }
into g // and we are calling the grouping 'g'
select g; // select the group
// example of doing something with the groupings
foreach (var group in groups)
{
var key = group.Key; // gets a { ProjId, SubProjId } tuple
foreach (var work in group)
{
// each work is a row in the Work-table
}
}