Develop Reference

LINQ: equivalent for string_agg from PostgreSql

I need to concatenate multiple columns values to single value (separated with coma for example). I can do it by string_agg(u.name, ',') as Users in PostgreSql. I tried do it in linq query syntax but I failed - all time I just get list with split values instead of one row with values concatenated in one field.
Let's assume that I have only three tables:
Doc User Doc_User
+----+--------------------+ +----+-----------+ +----+-----------+
| Id | Path | | Id | Name | | DocId | UserId |
+----+--------------------+ +----+-----------+ +----+-----------+
| 1 | "C:\\Files\\A.txt" | | 1 | "Adam" | | 1 | 1 |
| 2 | "C:\\Files\\B.txt" | | 2 | "Benny" | | 1 | 2 |
| 3 | "C:\\Files\\C.txt" | | 3 | "Charlie" | | 2 | 1 |
+----+--------------------+ +----+-----------+ | 2 | 2 |
| 2 | 3 |
+-------+--------+
At the start I was trying simple join:
var model = (from d in db.Docs
join du in db.DU on d.Id equals du.DocId
join u in db.Users on du.UserId equals u.Id
select new DataModel() { DocPath = d.Path, UserName = u.Name }).ToList();
As I suspected I got list with separated rows:
C:\Files\A.txt | Adam
C:\Files\A.txt | Benny
C:\Files\B.txt | Adam
C:\Files\B.txt | Benny
C:\Files\B.txt | Charlie
But what I want to obtain is:
C:\Files\A.txt | Adam, Benny
C:\Files\B.txt | Adam, Benny, Charlie
string.Join() is not recognized by EF and I can't use it in linq queries, Aggregate() not working too. How can I achieve this?
I've prepared example for play with it: .Net Fiddle.

The code below groups the common documents by path using LINQ and then joins the grouped document's UserNames, using string.Join. I also think you don't need ToList() in this line select new DataModel() { DocPath = d.Path, UserName = u.Name }).ToList(); if you are going to use this solution because we are going to use LINQ again.
var grouped = model.GroupBy(x => x.DocPath);
foreach (var iGrouped in grouped){
string.Join(",",iGrouped.Select(x => x.UserName));
Console.WriteLine(iGrouped.Key + " | " + string.Join(",",iGrouped.Select(x => x.UserName)));
}

Combine datatables with specific conditions

UPDATED: Forgot to mention, the table may contain more than one type of itemcode
I've got a problem for datatable. There're total 14 items with same itemcode. And now there're 2 tables come from different source. One is grouped by itemcode and sum up the quantity, when count equals to 10, go to next row, and each row contains specific information such as shipment and remarks. Another table contains more detail information.
Source1: Grouped table
ItemCode|TotalQty|Shipment|Remarks|Line
=========================================
ITEM01 | 1000 | S001 | R001 | 1 <==10 items here
ITEM01 | 400 | S002 | R002 | 2 <==4 items here
Source2: Detail table (14 items & rows)
RefNo|ItemCode|Quantity|Weight|From
=======================================
R001 | ITEM01 | 100 | 50 | US
R002 | ITEM01 | 100 | 50 | US
R003 | ITEM01 | 100 | 50 | US
. | . | . | . | .
. | . | . | . | .
R013 | ITEM01 | 100 | 50 | US
R014 | ITEM01 | 100 | 50 | US
I would like to combine source1 and source2 and get the result as below
Shipment|Line|Remarks|ItemCode|TotalQty|RefNo|Quantity|Weight|From
===================================================================
S001 | 1 | R001 | ITEM01 | 1000 | R001| 100 | 50 | US \\1
S001 | 1 | R001 | ITEM01 | 1000 | R002| 100 | 50 | US \\2
S001 | 1 | R001 | ITEM01 | 1000 | R003| 100 | 50 | US \\3
S001 | 1 | R001 | ITEM01 | 1000 | R004| 100 | 50 | US \\4
S001 | 1 | R001 | ITEM01 | 1000 | R005| 100 | 50 | US \\5
S001 | 1 | R001 | ITEM01 | 1000 | R006| 100 | 50 | US \\6
S001 | 1 | R001 | ITEM01 | 1000 | R007| 100 | 50 | US \\7
S001 | 1 | R001 | ITEM01 | 1000 | R008| 100 | 50 | US \\8
S001 | 1 | R001 | ITEM01 | 1000 | R009| 100 | 50 | US \\9
S001 | 1 | R001 | ITEM01 | 1000 | R010| 100 | 50 | US \\10
S002 | 2 | R002 | ITEM01 | 400 | R011| 100 | 50 | US \\11
S002 | 2 | R002 | ITEM01 | 400 | R012| 100 | 50 | US \\12
S002 | 2 | R002 | ITEM01 | 400 | R013| 100 | 50 | US \\13
S002 | 2 | R002 | ITEM01 | 400 | R014| 100 | 50 | US \\14
Is there any way (Linq or looping) to get the above result? Thanks for your help!

It can be done with LINQ (which I assume you're after, since you've included the LINQ tag), but not in what I would consider a nice fashion.
Given two DataTable objects with the above formats and data, named grouped and detail, here's a LINQ expression that will stitch the data together in the way you want:
IEnumerable<object[]> qry =
(
from DataRow rDetail in detail.Rows
let dgrp = detail.Rows.IndexOf(rDetail) / 10
join DataRow rGroup in grouped.Rows
on dgrp equals grouped.Rows.IndexOf(rGroup)
orderby rDetail["RefNo"]
select new object[] {
rGroup["Shipment"], rGroup["Line"], rGroup["Remarks"], rGroup["ItemCode"], rGroup["TotalQty"],
rDetail["RefNo"], rDetail["Quantity"], rDetail["Weight"], rDetail["From"]
}
);
Now you need another DataTable to pump those results into:
DataTable res = new DataTable();
res.Columns.Add("Shipment", typeof(string));
res.Columns.Add("Line", typeof(Int32));
res.Columns.Add("Remarks", typeof(string));
res.Columns.Add("ItemCode", typeof(string));
res.Columns.Add("TotalQty", typeof(Int32));
res.Columns.Add("RefNo", typeof(string));
res.Columns.Add("Quantity", typeof(Int32));
res.Columns.Add("Weight", typeof(Int32));
res.Columns.Add("From", typeof(string));
And finally, fill the res table with the results of the LINQ query:
foreach (object[] rowdata in qry)
res.Rows.Add(rowdata);
The code above works for this specific set of data, but I can't promise you anything more than that. It is heavily dependent on the row order in the source tables, and because I'm using DataTable.Rows.IndexOf to get the order it's quite possible that this will be terribly slow on large collections of data.
But then you're already using DataTables instead of a properly typed collection, so all bets are off in the performance- and code-sanity stakes anyway.
This is one case where I'd suggest not using LINQ to perform the task. IMHO this would be better done as an iterative loop rather than a query. You don't get much (if any) improvement over the iterative version, you lose a lot of clarity, and you have all sorts of fun getting things set up just right before you can use it.
And because I can't leave well-enough alone, here's a full (long, lots of code) solution using a combination of LINQ, classes to hold the data being processed and iteration to generate the table:
public DataTable MergeShippingData(DataTable groupTable, DataTable detailTable)
{
// convert group table to array of GroupEntry objects
var groupList =
(
from DataRow grouprow in groupTable.Rows
let ent = GroupEntry.FromRow(grouprow)
where ent != null
select ent
).ToArray();
// convert detail table to sequence of DetailEntry objects
var detailSeq =
from DataRow detailrow in detailTable.Rows
let ent = DetailEntry.FromRow(detailrow)
where ent != null
select ent;
// Create output DataTable
DataTable output = CreateOutputTable();
// Process all detail lines into shippings
foreach (var detail in detailSeq)
{
// Find available shipping group for the item code with enough remaining capacity
var grp = groupList.First (g => g.ItemCode == detail.ItemCode && g.Remainder >= detail.Quantity);
if (grp == null)
throw new Exception("No available shipping found for detail item...");
// update remaining space in shipping group
grp.Remainder -= detail.Quantity;
// add data to output table
output.Rows.Add(new object[] {
grp.Shipment, grp.Line, grp.Remarks, grp.ItemCode, grp.TotalQty,
detail.RefNo, detail.Quantity, detail.Weight, detail.From
});
}
return output;
}
// Class to hold the shipping groups while processing
public class GroupEntry
{
// fields from source DataTable
public string ItemCode;
public int TotalQty;
public string Shipment;
public string Remarks;
public int Line;
// process variable, holds remaining quantity value
public int Remainder;
// Convert DataRow into GroupEntry
public static GroupEntry FromRow(DataRow r)
{
try
{
return new GroupEntry
{
ItemCode = r.Field<string>(0),
TotalQty = r.Field<int>(1),
Shipment = r.Field<string>(2),
Remarks = r.Field<string>(3),
Line = r.Field<int>(4),
Remainder = r.Field<int>(1)
};
}
catch { }
return null;
}
}
// Class to hold shipping Detail records during processing
public class DetailEntry
{
public string RefNo;
public string ItemCode;
public int Quantity;
public int Weight;
public string From;
// Convert DataRow into DetailEntry
public static DetailEntry FromRow(DataRow r)
{
try
{
return new DetailEntry
{
RefNo = r.Field<string>(0),
ItemCode = r.Field<string>(1),
Quantity = r.Field<int>(2),
Weight = r.Field<int>(3),
From = r.Field<string>(4)
};
}
catch { }
return null;
}
}
// Create output DataTable
public DataTable CreateOutputTable()
{
DataTable res = new DataTable();
res.Columns.Add("Shipment", typeof(string));
res.Columns.Add("Line", typeof(Int32));
res.Columns.Add("Remarks", typeof(string));
res.Columns.Add("ItemCode", typeof(string));
res.Columns.Add("TotalQty", typeof(Int32));
res.Columns.Add("RefNo", typeof(string));
res.Columns.Add("Quantity", typeof(Int32));
res.Columns.Add("Weight", typeof(Int32));
res.Columns.Add("From", typeof(string));
return res;
}
Add some error handling and you're good to go.

Querying highest value by keys from database

With the following table:
+-------------+-----------+---------+
| Parent_ID | Item_ID | Count |
+-------------+-----------+---------+
| 1 | 1 | 1 |
| 1 | 1 | 5 |
| 1 | 1 | 4 |
| 1 | 2 | 7 |
| 1 | 2 | 2 |
| 2 | 1 | 2 |
| 2 | 1 | 3 |
| 2 | 2 | 2 |
| 2 | 2 | 4 |
+-------------+-----------+---------+
I would like to get the highest available count for given Parent_ID and Item_ID, like the following:
+-------------+-----------+---------+
| Parent_ID | Item_ID | Count |
+-------------+-----------+---------+
| 1 | 1 | 5 |
| 1 | 2 | 7 |
| 2 | 1 | 3 |
| 2 | 2 | 4 |
+-------------+-----------+---------+
How would I go about doing this using LINQ/SQL in C#? For example, I would like the highest item counts for parent id 1. This would be something like:
int parentId = 1;
var counts = from c in database.Items where parentId == c.parentId
//this gets all counts from items for parent id 1, but I am just looking
//for the highest count per item for parent id 1

SELECT Parent_ID, Item_ID, MAX(Count)
FROM ...
GROUP BY Parent_Id, Item_ID

select parent_id,
item_id,
max(count) as count
from your_table
group by parent_id, item_id

To group by multiple fields, you can group using an anonymous object:
var counts = from item in database.Items
group item by new { item.ParentId, item.ItemId } into itemGroup
select new Item()
{
ParentId = itemGroup.Key.ParentId,
ItemId = itemGroup.Key.ItemId,
Count = itemGroup.Max(x => x.Count)
};

Using LINQ2SQL I think you want something like:
var counts = database.Items.GroupBy(p => p.parentId).Max(p => p.Key);

linq query sum products across multiple collections

I have two datasets that look like this:
+------------------------------------+
| Products |
+------------------------------------+
| Id | Name | Price |
+------------------------------------+
| 1 | apples | 1.00 |
| 2 | oranges | 2.00 |
| 3 | pomengrate | 3.00 |
+------------------------------------+
+-------------------------------+
| Sales |
+-------------------------------+
| CustId | ProductId | Quantity |
+-------------------------------+
| 1 | 1 | 5 |
| 1 | 2 | 4 |
| 1 | 3 | 2 |
| 2 | 1 | 8 |
| 2 | 3 | 7 |
+-------------------------------+
I want to get the amount that each customer is spending, essentially ending up with a result like this:
+----------------+
| CustId | Total |
+----------------+
| 1 | 19.00 |
| 2 | 29.00 |
+----------------+
I can do a sum across a single table but the Sum method in LINQ takes a lambda with only one argument: the reference to the table that the values being summed are in. These values are in different tables. How do I sum these together?

var totals =
from sale in Sales
group sale by sale.CustId into custSales
select new
{
CustId = custSales.Key,
Total = (
from custSale in custSales
select custSale.Product.Price *
custSale.Quantity)
.Sum()
};

Give this a shot. It gives the results you were looking for:
var results = sales.Join(products,
sale => sale.ProductID,
product => product.ID,
(sale, product) => new { CustID = sale.CustID, Total = sale.Quantity * product.Price })
.GroupBy(r => r.CustID)
.Select(g => new { CustID = g.Key, Total = g.Sum(gt => gt.Total) });

For completeness sake, here's the query syntax version (utilizing joins as opposed to a subselect):
var totals =
from sale in sales
join prod in product on sale.ProductId equals prod.Id
let saleProds = new { sale.CustId, Total = prod.Price * sale.Quantity }
group saleProds by saleProds.CustId into custSale
select new { Customer = custSale.Key, Total = custSale.Sum(tr => tr.Total) };
The key part is that you need to somehow transform the joined collection results (sale and prod) into a single entity that can then be grouped by.

Query tabels to sort sums across rows and count based on a value in LINQ

Here is my problem. i have 3-5 persons that is going to set a grade on one person and they use their own individual row to do so, and what I'm having trouble to do is to sum and average the grade from individual data across multiple rows on the same table.
in the select new statement i have made a pseudo answer of what i want
var users = from workRew in db.Reviews
select new
{
UserID = workRew.UserID.DistinctOfSomeSort
AvgGrade = workRew.Grade.Sum/CountOfSomeSort
};
Here i a illustration.
So if i have this table
| SomeID | UserID | Grade |
| 1 | 2 | 3 |
| 2 | 3 | 1 |
| 3 | 2 | 1 |
And this is the output i want from the LINQ query on the above (In theory ateast)
| UserID | AvgGrade |
| 2 | 2 |
| 3 | 1 |
EDIT: Simplified the whole case, to a great extent.

It should look something like this fragment:
group by user.UserID
select new
{
User = user.UserID
TotGradeCount = workRew.Grade.Sum()
Graders = workRew.Grade.Count()
}