Develop Reference

Retrieving a row value based on other columns value using linq

I have three data tables that basically contain the following data:
table 1:
ID FContractID | WaitingTime
1 | 1 | 85
2 | 1 | 98
3 | 1 | 122
4 | 1 | 45
5 | 1 | 234
6 | 1 | 101
etc.
Table 2:
PricingCriterionItemId PricingCriterionName PricingCriterionUnit
1 | WaitingTimeMax | min
2 | WaitingTimePeriod | min
3 | WaitingTimeOverdue | €/period
4 | OverDuePriceMax | €
Table 3:
PricingCriterionId ContractID PricingCriterionItemId PricingCriterionValue
1 | 1 | 1 | 70
2 | 1 | 2 | 30
3 | 1 | 3 | 30,00
4 | 1 | 4 | 120,00
I want to add to the table 1 a column that contains waiting time cost. The waiting time cost would be calculated like
WaitingTimeCost = min(((WaitingTime - WaitingTimeMax) / WaitingTimePeriod) * WaitingTimeOverdue, OverDuePriceMax)
I can easily join tables 2 and 3 into one table:
Table 4
PricingCriterionId ContractID PricingCriterionName PricingCriterionValue PricingCriterionUnit
1 | 1 | WaitingTimeMax | 70 | min
2 | 1 | WaitingTimePeriod | 30 | min
3 | 1 | WaitingTimeOverdue | 30,00 | €/period
4 | 1 | OverDuePriceMax | 120,00 | €
Is it possible using linq to assign a column's value on a certain row using other columns value?
Something like
var result = from WaitingData in table1
join PricingCriteria in table4
on WaitingData.ContractId equals PricingCriteria.ContractId
let WaitingTimeMax = (select PricingCriterionValue from table4 where PricingCriterionName = "WaitingTimeMax")
let ...
let WaitingTimeCost = min(((WaitingTime - WaitingTimeMax) / WaitingTimePeriod) * WaitingTimeOverdue, OverDuePriceMax)
select new
{
ID,
WaitingTimeCost
}
How to formulate this properly using linq?

You don't need to do everything in the database query.
Database is only IO device, which responsible only for reading and writing data.
Load all required data and calculate.
var contractsId = waitingData.Select(data => data.ContractId).ToList();
var pricingCriterias = table4.Where(criteria => contractsId.Contains(criteria.ContractId)
.ToLookup(criteria => criteria.ContractId);
var maxWaitingTime =
pricingCriterias.SelectMany(group => group)
.Where(criteria => criteria.PricingCriterionName = "WaitingTimeMax")
.Max(criteria => criteria.PricingCriterionValue);
foreach (var waitingItem in waitingData)
{
// Calculate others waiting values
var waitingPerPeriod = (WaitingTime - maxWaitingTime) / WaitingTimePeriod);
var waitingPrice = waitingPerPeriod * WaitingTimeOverdue;
var WaitingTimeCost = Math.Min(waitingPrice, OverDuePriceMax)
}
Below example with DataTables.
However DataTable is heavy and not strongly typed data structure and as developer it takes more time to deal with it.
Instead transform data in DataTable to the plain strong typed objects with descriptive property names - you will get IntelliSense for free ;)
var contractsId =
waitingData.AsEnumerable()
.Select(row => row.Field<int>("ContractId"))
.ToList();
var pricingCriterias =
table4.AsEnumerable()
.Where(row => contractsId.Contains(row => row.Field<int>("ContractId"))
.ToLookup(row => row.Field<int>("ContractId"));
var maxWaitingTime =
pricingCriterias.SelectMany(group => group)
.Where(row => row.Field<string>("PricingCriterionName") = "WaitingTimeMax")
.Max(row => row.Field<int>("PricingCriterionValue"));
foreach (var waitingItem in waitingData)
{
// Calculate others waiting values
var waitingPerPeriod = (WaitingTime - maxWaitingTime) / WaitingTimePeriod);
var waitingPrice = waitingPerPeriod * WaitingTimeOverdue;
var WaitingTimeCost = Math.Min(waitingPrice, OverDuePriceMax)
}

Is there an easy way to INNER join , OUTER join , LEFT OUTER join, RIGHT OUTER join, or UNION two (or more) DataTables in C#?

I am writing a c# application that connects separate database systems. These systems could be flat-file db's, Oracle, Sql, Excel Files, ext. The job of the C# application is to provide an outlet for making all of these sources available in one spot. So basically, the application accepts a list of queries and connection settings for the respective database systems and collects a bunch of results.
The goal is to output a singe DataTable with the result of all these queries all joined/unioned together(depending on settings). Does C# provide an easy way to perform any join/union operations on a list of DataTables?
For example:
Table1:
__________________________________________________________
|tb1_pk_id| tb1_name | tb1_data1 | tb1_data2 |
|---------|---------------|---------------|---------------|
| 1 | tb1name_blah1 | tb1dat1_blah1 | tb1dat2blah1 |
| 2 | tb1name_blah2 | tb1dat1_blah2 | tb1dat2blah2 |
| 3 | tb1name_blah3 | tb1dat1_blah3 | tb1dat2blah3 |
-----------------------------------------------------------
Table2:
__________________________________________________________
|tb2_pk_id| tb2_name | tb2_data1 | tb2_data2 |
|---------|---------------|---------------|---------------|
| 1 | tb2name_blah1 | tb2dat1_blah1 | tb2dat2blah1 |
| 2 | tb2name_blah2 | tb2dat1_blah2 | tb2dat2blah2 |
| 3 | tb2name_blah3 | tb2dat1_blah3 | tb2dat2blah3 |
-----------------------------------------------------------
Join Results:
__________________________________________________________ _______________________________________________
|tb1_pk_id| tb1_name | tb1_data1 | tb1_data2 | tb2_name | tb2_data1 | tb2_data2 |
|---------|---------------|---------------|---------------|---------------|---------------|---------------|
| 1 | tb1name_blah1 | tb1dat1_blah1 | tb1dat2blah1 | tb2name_blah1 | tb2dat1_blah1 | tb2dat2blah1 |
| 2 | tb1name_blah2 | tb1dat1_blah2 | tb1dat2blah2 | tb2name_blah2 | tb2dat1_blah2 | tb2dat2blah2 |
| 3 | tb1name_blah3 | tb1dat1_blah3 | tb1dat2blah3 | tb2name_blah3 | tb2dat1_blah3 | tb2dat2blah3 |
-----------------------------------------------------------------------------------------------------------
So far I have found the following code online (here) to do a merge on all the data:
private DataTable MergeAll(IList<DataTable> tables, String primaryKeyColumn)
{
if (!tables.Any())
throw new ArgumentException("Tables must not be empty", "tables");
if (primaryKeyColumn != null)
foreach (DataTable t in tables)
if (!t.Columns.Contains(primaryKeyColumn))
throw new ArgumentException("All tables must have the specified primarykey column " + primaryKeyColumn, "primaryKeyColumn");
if (tables.Count == 1)
return tables[0];
DataTable table = new DataTable("TblUnion");
table.BeginLoadData(); // Turns off notifications, index maintenance, and constraints while loading data
foreach (DataTable t in tables)
{
table.Merge(t); // same as table.Merge(t, false, MissingSchemaAction.Add);
}
table.EndLoadData();
if (primaryKeyColumn != null)
{
// since we might have no real primary keys defined, the rows now might have repeating fields
// so now we're going to "join" these rows ...
var pkGroups = table.AsEnumerable()
.GroupBy(r => r[primaryKeyColumn]);
var dupGroups = pkGroups.Where(g => g.Count() > 1);
foreach (var grpDup in dupGroups)
{
// use first row and modify it
DataRow firstRow = grpDup.First();
foreach (DataColumn c in table.Columns)
{
if (firstRow.IsNull(c))
{
DataRow firstNotNullRow = grpDup.Skip(1).FirstOrDefault(r => !r.IsNull(c));
if (firstNotNullRow != null)
firstRow[c] = firstNotNullRow[c];
}
}
// remove all but first row
var rowsToRemove = grpDup.Skip(1);
foreach (DataRow rowToRemove in rowsToRemove)
table.Rows.Remove(rowToRemove);
}
}
return table;
}
This works fine for doing a union, but I don't know if an easier way to do that already exists in .NET that will let me do ANY kind of join or union on a group of seprate DataTables (not just the union as in the code above) or do I have to custom code each type of join/union?

No, there is not a simple .Net way of doing this....
LINQ can come close... you can create table joins in LINQ, but they are typically "inner joins". Doing a "left join" is a bit more complicated and requires the GroupJoin keyword.
https://msdn.microsoft.com/en-us/library/bb386969(v=vs.110).aspx
If you'd like "do it yourself" with ADO.Net DataRelations, you might take a look at this old VB.Net article:
http://www.emmet-gray.com/Articles/DataRelations.html

C# ObservableCollection get all values where Id is identical

How could I get all rows, where my Id (it is meant to be like that) is x.
Example list:
| Id | Key | Value |
----------------------
| 0 | FName | Peter |
| 0 | LName | Griff |
| 0 | Phone | 12345 |
| 1 | FName | Sasha |
| 1 | LName | Un |
| 1 | Mail | SU#m.c|
| 2 | FName | Laura |
...
From the list I want to get all 0 and 1... differently to insert them into Sharepoint list.
This data has been inserted to this Collection before and Id is used to keep information for specific person.
All I could come up currently is to use loops, to do that
for (int i = 0; i < _dataVm.ADData.Count; i++)
{
foreach (DataFromAD k in _dataVm.ADData)
{
// Not sure, how could I sort out specific data here
}
}

You have to group data on Id using groupby to get seperated items by Id:
var result = from d in _dataVm.ADData
group d by d.Id into g
select new
{
Id = g.Key,
Data = g.ToList()
}

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()
}