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C# Linq To Create Group On Multiple Properties and format the resultant group into single key/property?

I have following scenario where I want to find duplicates after forming the group and realign/format the duplicate data with some common class.
Example -
var lst = new List<Test>
{
new Test{Category="A",Class="Class1",Id="101",Name="John"},
new Test{Category="B",Class="Class2",Id="102",Name="Peter"},
new Test{Category="A",Class="Class2",Id="103",Name="David"},
new Test{Category="C",Class="Class3",Id="104",Name="Julia"},
new Test{Category="D",Class="Class4",Id="105",Name="Ken"},
new Test{Category="A",Class="Class1",Id="106",Name="Robert"},
};
I have created the group as -
var group =
from c in lst
group c by new
{
c.Category,
c.Class
} into g
select new
{
Category = g.Key.Category,
Class = g.Key.Class,
Id = lst.Where(x => g.Key.Category == x.Category && g.Key.Class==x.Class)
.Select(y => y.Id).ToList()
};
Which results me 2 group items for Category A with different Classes -
GroupItem1 - Category = "A" , Class = "Class1", Id = {101,106}
GroupItem2 - Category = "A" , Class = "Class2", Id = {103}
So I have requirement to show result in such case as below with other categories as -
Category = "A", Class = "Class1 OR SomeCommonClass", Id = {101,106,103}
Is it possible to achieve this result with minimum code and optimized logic.

If you want to group by Category and get the result below is the query.
var group =
from c in lst
group c by new
{
c.Category
} into g
select new
{
Category = g.Key.Category,
Class = lst.Where(x => g.Key.Category == x.Category).Select(y => y.Class).ToList(),
Id = lst.Where(x => g.Key.Category == x.Category)
.Select(y => y.Id).ToList()
};

Replace your group query with this:
var groups =
from c in lst
group c by c.Category into g
select new { Category = g.Key, Class = g.Select(c => c.Class).Distinct().Join(" or "), IDs = g.Select(c => c.Id).ToList() };
where Join is an IEnumerable extension method:
public static string Join(this IEnumerable<string> strings, string sep) => String.Join(sep, strings.ToArray());

var group = lst.GroupBy(l => l.Category)
.Select(x => new
{
Category = x.Key,
Class = string.Join(" OR ", x.Select(c => c.Class).Distinct()),
Ids = x.Select(c => c.Id).ToList()
}).ToList();

Include count = 0 in linq results

I have a table having TeamName and CurrentStatus fields. I am making a linq query to get for each team and for each status the count of records:
var teamStatusCounts = models.GroupBy(x => new { x.CurrentStatus, x.TeamName })
.Select(g => new { g.Key, Count = g.Count() });
The results of this query returns all the counts except where count is 0. I need to get the rows where there is no record for a specific team and a specific status (where count = 0).

You could have a separate collection for team name and statuses you are expecting and add the missing ones to the result set
//assuming allTeamNamesAndStatuses is a cross joing of all 'CurrentStatus' and 'TeamNames'
var teamStatusCounts = models.GroupBy(x => new { x.CurrentStatus, x.TeamName })
.Select(g => new { g.Key, Count = g.Count() })
.ToList();
var missingTeamsAndStatuses = allTeamNamesAndStatuses
.Where(a=>
!teamStatusCounts.Any(b=>
b.Key.CurrentStatus == a.CurrentStatus
&& b.Key.TeamName == a.TeamName))
.Select(a=>new {
Key = new { a.CurrentStatus, a.TeamName },
Count = 0
});
teamStatusCounts.AddRange(emptyGroups);
I've created a fiddle demonstrating the answer as well

I would select the team names and status first:
var teams = models.Select(x => x.TeamName).Distinct().ToList();
var status = models.Select(x => x.CurrentStatus).Distinct().ToList();
You can skip this if you know the list entries already.
Then you can select for each team and each state the number of models:
var teamStatusCounts = teams.SelectMany(team => states.Select(state =>
new
{
TeamName = team,
CurrentStatus = state,
Count = models.Count(model =>
model.TeamName == team && model.CurrentStatus == state)
}));

C# lambda-> All rows Select Add Row_Number

I have a table:
DataTable store_temp = new DataTable();
store_temp.Columns.Add("patn");
store_temp.Columns.Add("rf");
store_temp.Columns.Add("name");
store_temp.Columns.Add("conv");
store_temp.Columns.Add("conv_type");
store_temp.Columns.Add("recorddate");
store_temp.Columns.Add("executiondate");
My C# code :
int i = 0;
var rowsgroups = (from row in store_temp.AsEnumerable().GroupBy(row =>
row.Field<string>("patn"))
.OrderBy((g => g.OrderByDescending(y => y.Field<string("executiondate")).ThenByDescending(y =>
y.Field<string>("rf"))))
select new
{
patn = row.ElementAt(i),
rf_num = ++i,
}).ToArray();
I want the lambda experession, which is equivalent to:
select patn, rf,
> row_number() over( partition by patn order by executiondate,rf )
as rf_num,
name, conv,conv_type, recorddate, executiondate
from store_temp2
But, lambda syntax ... var rowsgroups has just a one row..
I want to show all rows in store_temp.
What should I do to fix the query?

row_number() over(partition by patn order by executiondate, rf)
means in LINQ you need to group by patn, then order each group by executiondate, rf, then use the indexed Select overload to get row numbering inside the group, and finally flatten the result with SelectMany.
With that being said, the equivalent LINQ query could be something like this:
var result = store_temp.AsEnumerable()
.GroupBy(e => e.Field<string>("patn"), (key, elements) => elements
.OrderBy(e => e.Field<string>("executiondate"))
.ThenBy(e => e.Field<string>("rf"))
.Select((e, i) => new
{
patn = key,
rf = e.Field<string>("rf"),
rf_num = i + 1,
name = e.Field<string>("name"),
conv = e.Field<string>("conv"),
conv_type = e.Field<string>("conv_type"),
recorddate = e.Field<string>("recorddate"),
executiondate = e.Field<string>("executiondate")
}))
.SelectMany(elements => elements)
.ToArray();

Try something like this
select new
{
rowNum = store_temp.Rows.IndexOf(row),
patn = row.ElementAt(i),
rf_num = ++i,
}).ToArray();

I don't think you required any groupby as per your required sql
var i=0;
var rowsgroups = (from row in store_temp.AsEnumerable()
orderby row.Field<string>("executiondate") descending,
row.Field<string>("rf") descending
select new
{
patn = row.Field<string>("patn"),
rf_num = ++i,
name = row.Field<string>("name"),
conv = row.Field<string>("conv"),
conv_type = row.Field<string>("conv_type"),
recorddate = row.Field<string>("recorddate"),
executiondate = row.Field<string>("executiondate")
}).ToArray();

Linq ordering output

I am trying to sort a listbox by the customerID and then by Total (discount*unitPrice*quantity) and cannot manage to organize the code in a way that will sort it in that way. Any help would be greatly appreciated.
HERE is a link showing an image on how the results should be returned as.
var load1 = System.IO.File.ReadAllLines(#"c:\temp\AS3Products.csv")
.Select(x => new
{
CID = x.Split(',')[0],
discount = x.Split(',')[2].Trim(),
productId = x.Split(',')[0].Trim()
});
var load2 = System.IO.File.ReadAllLines(#"c:\temp\AS3Transactions.csv")
.Select(x => new
{
productId = x.Split(',')[3],
unitPrice = x.Split(',')[4],
quantity = x.Split(',')[5]
});
var querypractice = from x in load1
join y in load2 on x.productId equals y.productId
where x.CID == "110"
orderby x.discount, y.quantity
select new { x.CID, x.discount, x.productId, y.quantity, y.unitPrice };
foreach (var x in querypractice)
{
double total = double.Parse(x.quantity) * double.Parse(x.unitPrice) * double.Parse(x.discount);
listBox1.Items.Add(x.CID+ " " +x.discount+" "+x.quantity+ " " + total);
}

Disclaimer: I don't have VS on this machine, so this isn't validated, but I think you can do it using the LET statement to set up the calculated value, then order based on it.
var querypractice = from x in load1
join y in load2 on x.productId equals y.productId
let total = x.discount*x.unitPrice*x.quantity
where x.CID == "110"
orderby x.CID, total
select new { x.CID, total };
http://www.codeproject.com/Articles/231164/Into-and-let-in-LINQ-Let-vs-Into

If you're positive that these files have numbers in the expected places all the time, you could parse them as you read them from the files. Otherwise, you'll want to do some validation first or you'll get exceptions.
(I changed double.Parse to decimal.Parse - it's more accurate for manipulating dollar amounts.)
var load1 = System.IO.File.ReadAllLines(#"c:\temp\AS3Products.csv")
.Select(x => new
{
CID = int.Parse(x.Split(',')[0]),
discount = decimal.Parse(x.Split(',')[2].Trim()),
productId = int.Parse(x.Split(',')[0].Trim())
});
var load2 = System.IO.File.ReadAllLines(#"c:\temp\AS3Transactions.csv")
.Select(x => new
{
productId = int.Parse(x.Split(',')[3]),
unitPrice = decimal.Parse(x.Split(',')[4]),
quantity = int.Parse(x.Split(',')[5])
});
Then you can create your list like this. (I removed the specific id you had in your query.)
var orderedList = (from x in load1
join y in load2 on x.productId equals y.productId
let total = (x.discount * y.unitPrice * y.quantity)
orderby x.CID descending, total descending
select new
{
x.CID,
x.discount,
x.productId,
y.quantity,
y.unitPrice
});

C# Linq Average

I have a table with data similar to below:
Group TimePoint Value
1 0 1
1 0 2
1 0 3
1 1 3
1 1 5
I want to project a table as such:
Group TimePoint AverageValue
1 0 2
1 1 4
EDIT: The data is in a datatable.
Anybody any ideas how this can be done with LINQ or otherwise?
Thanks.

You need to perform Group By
The linq you need is something like:
var query = from item in inputTable
group item by new { Group = item.Group, TimePoint = item.TimePoint } into grouped
select new
{
Group = grouped.Key.Group,
TimePoint = grouped.Key.TimePoint,
AverageValue = grouped.Average(x => x.Value)
} ;
For more Linq samples, I highly recommend the 101 Linq samples page - http://msdn.microsoft.com/en-us/vcsharp/aa336747#avgGrouped

Here's a more function-oriented approach (the way I prefer it). The first line won't compile, so fill it in with your data instead.
var items = new[] { new { Group = 1, TimePoint = 0, Value = 1} ... };
var answer = items.GroupBy(x => new { TimePoint = x.TimePoint, Group = x.Group })
.Select(x => new {
Group = x.Key.Group,
TimePoint = x.Key.TimePoint,
AverageValue = x.Average(y => y.Value),
}
);

You can do:
IEnumerable<MyClass> table = ...
var query = from item in table
group item by new { item.Group, item.TimePoint } into g
select new
{
g.Key.Group,
g.Key.TimePoint,
AverageValue = g.Average(i => i.Value)
};

Assuming a class like this:
public class Record
{
public int Group {get;set;}
public int TimePoint {get;set;}
public int Value {get;set;}
}
var groupAverage = from r in records
group r by new { r.Group, r.TimePoint } into groups
select new
{
Group = groups.Key.Group,
TimePoint = groups.Key.TimePoint,
AverageValue = groups.Average(rec => rec.Value)
};