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Linq : Use variable in a GroupBy

I have help this LINQ request :
My c#:
var stats = UoW.Repository
.Get(echangeFilter)
.GroupBy(a => new
{
Id = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()).id : MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault()).id,
Tri = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()).Tri: MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault()).Tri,
SensAppel = a.echange_sens.nom
})
.Select(group => new
{
group.Key.Id,
group.Key.Tri,
group.Key.SensAppel,
Count = group.Count(),
})
.OrderBy(g => g.Tri)
.ToList();
It works but I want to remove this horrible duplication (Id and Tri) in this groupBy, how can I deal with that ? In the concept, I want to use a variable to call this ternary once

If you use the query syntax, you can declare variables.
This is how your query would look like in query syntax (please name your variables properly. I don't know what you are actually doing so I can't name them...):
var query = from a in UoW.Repository
.Get(echangeFilter)
group a by new
{
Id = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()).id : MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault()).id,
Tri = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()).Tri: MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault()).Tri,
SensAppel = a.echange_sens.nom
} into g
let b = new
{
group.Key.Id,
group.Key.Tri,
Count = group.Count(),
}
orderby g.Tri
select g;
var stats = query.ToList();
Now we can introduce a let:
var query = from a in UoW.Repository
.Get(echangeFilter)
let x = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()) : MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault())
group a by new
{
Id = x.id,
Tri = x.Tri,
SensAppel = a.echange_sens.nom
} into g
let b = new
{
g.Key.Id,
g.Key.Tri,
Count = g.Count(),
}
orderby g.Tri
select g;
var stats = query.ToList();

Is this what you're looking for?
var stats = UoW.Repository
.GroupBy(a => {
var repo = MyBLL.IsInComing(a.idSens) ? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault()) : MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault())
return new
{
Id = repo.id,
Tri = repo.Tri,
SensAppel = a.echange_sens.nom
}
})
.Select(group => new
{
group.Key.Id,
group.Key.Tri,
Count = group.Count(),
})
.OrderBy(g => g.Tri)
.ToList();

This works by first returning whatever model FindByNoContactModel returns per record and SensAppel, so you only have to call the IsIncoming and FindByNoContactModel once per row. Depending on how many rows you expect to be returned, you may find very quickly that you are better off pushing these lookups elsewhere, or letting the database do it.
var stats = UoW.Repository
.Get(echangeFilter)
.Select(a=> new {
Model = MyBLL.IsIncoming(a.idSens)
? MyBLL.FindByNoContactModel(a.change.idTo.GetValueOrDefault())
: MyBLL.FindByNoContactModel(a.change.idFrom.GetValueOrDefault()),
SensAppel = a.echange_sens.nom
})
.GroupBy(a => new
{
Id = a.Model.id,
Tri = a.Model.Tri,
SensAppel = a.SensAppel
})
.Select(group => new
{
group.Key.Id,
group.Key.Tri,
group.Key.SensAppel,
Count = group.Count(),
})
.OrderBy(g => g.Tri)
.ToList();

You can combine the sub-expressions by pulling out the common elements and then using an intermediate anonymous class to hold them (I am not sure how EF 6 will handle this (what does Get return?) as I don't know what MyBLL is):
var stats = UoW.Repository
.Get(echangeFilter)
.Select(a => new {
a.echange_sens.nom,
fncm = MyBLL.FindByNoContactModel(
(MyBLL.IsInComing(a.idSens)
? a.change.idTo
: a.change.idFrom)
.GetValueOrDefault())
})
.GroupBy(nf => new {
Id = nf.fncm.id,
Tri = nf.fncm.Tri,
SensAppel = nf.nom
})
.Select(group => new {
group.Key.Id,
group.Key.Tri,
Count = group.Count(),
})
.OrderBy(g => g.Tri)
.ToList();

Execute query using LINQ or EF to fetch records from multiple tables

I've been searching for a while now. But all the solutions seems to be different than what I expect.
So this is my query in SQL:-
Select * from
(
select Name,Description Descr from CourseTbl
union all
select MainDesc Name,MainDesc Descr from CoursedescTbl
union all
select SubHeading Name,SubDesc Descr from CourseSubDesc
union all
select Name,Descr as Descr from InternTbl
)A where A.Name like '%D%' or A.Descr like '%D%'
I want to execute the above query using LINQ or EF. and return the list in Json format. So I tried many failed attempts and this is one of them:-
public JsonResult SearchDetail()
{
string SearchKey = Request.Form["SearchName"].ToString();
IEnumerable<SearchList> QueryResult;
using (EBContext db = new EBContext())
{
try
{
QueryResult =
(from x in db.Courses
select new { A = x.Name, B = x.Description })
.Concat(from y in db.CourseDesc
select new { A = y.MainHeading, B = y.MainDesc })
.Concat(from z in db.CourseSubDesc
select new { A = z.SubDesc, B = z.SubHeading })
.Concat(from w in db.Interns
select new { A = w.Name, B = w.Descr })
.ToList();
}
catch (Exception ex)
{
return new JsonResult
{
Data = ex.Message,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
return new JsonResult
{
Data = QueryResult,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
}
And my SearchList Class is like this:-
public class SearchList
{
public string Name { get; set; }
public string Descr { get; set; }
}
I'm not able to put the where clause in linq query which will search in all table.
I'm getting error when I assign queryresult to my ef query. It says cannot cast to Innumerable.
Thanks in Advance.

Could you explain more on the error you are getting?
Also, have you tried using .Union() in linq?
QueryResult = db.Courses.Select(x=> new { A = x.Name, B= x.Description})
.Union(db.CourseDesc.Select(y=> new {A = y.MainHeading, B = y.MainDesc })
.Union( //so on
.ToList(); //this isn't necessary
Edit: There are two ways to input where clause, either with each search, or at the end:
QueryResult = db.Courses.Where(x=>x.Name == "Name").Select(x=> new { A = x.Name, B= x.Description})
.Union(db.CourseDesc.Where(y=>y.MainHeading == "Name").Select(y=> new {A = y.MainHeading, B = y.MainDesc })
.Union( //so on
.ToList();
Or:
QueryResult = db.Courses.Where(x=>x.Name == "Name").Select(x=> new { A = x.Name, B= x.Description})
.Union(db.CourseDesc.Where(y=>y.MainHeading == "Name").Select(y=> new {A = y.MainHeading, B = y.MainDesc })
.Union( //so on
//Where can go either before or after .ToList
.Where(item=>item.A == "Name")
.ToList();

You did not say what error/exception you are getting. But your QueryResult is of type IEnumerable<SearchList> and you appear to be assigning it an enumerable of anonymous type { A, B }.
Try this:
QueryResult = (from x in db.Courses
select new SearchList { Name = x.Name, Descr = x.Description })
.Concat(...)
.ToList();
Or
QueryResult = db.Courses.Select(x => new SearchList
{ Name = x.Name, Descr = x.Description})
.Concat(...)
.ToList();
UPDATE
Your #2 issue will be fixed if you changed your select to new up a SearchList as I did above, instead of new-ing an anonymous type.
As for your issue #1, you should insert the Where() before your Select():
result1 = db.Courses
.Where(x => x.Name.Contains('D') || x.Description.Contains('D'))
.Select(x => new SearchList { Name = x.Name, Descr = x.Description});
result2 = db.CourseDesc
.Where(y => y.MainHeading.Contains('D') || y.MainDesc.Contains('D'))
.Select(y => new SearchList { Name = y.MainHeading, Descr = y.MainDesc});
result3 = db.CourseSubDesc
.Where(...)
.Select(...);
QueryResult = result1.Concat(result2).Concat(result3).ToList();
Doing Where() as part of the query on each table is important so you do not fetch all records from that table, unlike if you do the Where() after Concat(). Also note that Concat() may throw an ArgumentNullException.

Take the lists Separately and query and concat
check this example
List<string> a = new List<string>() { "a", "b", "c" };
List<string> b = new List<string>() { "ab", "bb", "cb" };
IEnumerable<SearchList> QueryResult =
a.Where(x => x.Contains("a")).Select(x => new SearchList() { Name = x, Descr = x })
.Concat(b.Where(x => x.Contains("a")).Select(x => new SearchList() { Name = x, Descr = x }));

Filter and add values using C# using lambda expression

New to C# and appreciate any help. The issue is that I need to filter the results of my api call against an array (using an "allowedA" and "allowedB" array.) I don't know how to edit the lambda expression to check against the loop.
var activities = await _restClientTaxonomy.GetTaxonomyFullAsync(TAXONOMY_CLASSIFICATIONID_FOR_ACTIVITY);
var activityTypes = await _restClientTaxonomy.GetTaxonomyFullAsync(TAXONOMY_CLASSIFICATIONID_FOR_ACTIVITY_TYPES);
var documentEventxx = activities.Select(type => type.Id);
long [] allowedA = new long []{ 7137, 40385637};
long [] allowedB = new long []{ 7137, 40385637};
foreach (long value in documentEventxx)
{
foreach (var item in allowed)
{
if (item == value) {
//These are the values I am looking for -> values that are part of the documentEventxx and allowedB.
}
}
}
var result = activityTypes.Select(type => new CategoryViewModel
{
Id = type.Id,//This is where I want to add only items that are in the allowedA array
Text = type.Name,
Types = activities.Where(a => a.ParentId == type.Id).Select(t => new TaxonomyMemberTextItem
{
Id = t.Id, //This is where I want to add only items that are in the allowedB array
Text = t.Name
}).ToList()
}).ToArray();
I have been reading about lambda expressions and foreach loops so please don't just post a random link.
Thanks in advance.

Filter the values before Selecting.
activityTypes.Where(x=>allowedA.Contains(x.Id)).Select(type => new CategoryViewModel
{
Id = type.Id,
Text = type.Name,
Types = activities.Where(a => a.ParentId == type.Id && allowedB.Contains(a.Id)).Select(t => new TaxonomyMemberTextItem
{
Id = t.Id,
Text = t.Name
}).ToList()
})

To filter you use .Where. You .Select to create a list of new types. So in order to filter, then create the lists of objects you want:
var result = activityTypes.Where(type=>isAllowed(type.Id)).Select(type => new CategoryViewModel
{
Id = type.Id,//This is where I want to add only items that are in the allowedA array
Text = type.Name,
Types = activities.Where(a => a.ParentId == type.Id&&isAllowed(a.Id)).Select(t => new TaxonomyMemberTextItem
{
Id = t.Id, //This is where I want to add only items that are in the allowedB array
Text = t.Name
}).ToList()
}).ToArray();

Assign values from one list to another using LINQ

Hello I have a little problem with assigning property values from one lists items to anothers. I know i could solve it "the old way" by iterating through both lists etc. but I am looking for more elegant solution using LINQ.
Let's start with the code ...
class SourceType
{
public int Id;
public string Name;
// other properties
}
class DestinationType
{
public int Id;
public string Name;
// other properties
}
List<SourceType> sourceList = new List<SourceType>();
sourceList.Add(new SourceType { Id = 1, Name = "1111" });
sourceList.Add(new SourceType { Id = 2, Name = "2222" });
sourceList.Add(new SourceType { Id = 3, Name = "3333" });
sourceList.Add(new SourceType { Id = 5, Name = "5555" });
List<DestinationType> destinationList = new List<DestinationType>();
destinationList.Add(new DestinationType { Id = 1, Name = null });
destinationList.Add(new DestinationType { Id = 2, Name = null });
destinationList.Add(new DestinationType { Id = 3, Name = null });
destinationList.Add(new DestinationType { Id = 4, Name = null });
I would like to achieve the following:
destinationList should be filled with Names of corresponding entries (by Id) in sourceList
destinationList should not contain entries that are not present in both lists at once (eg. Id: 4,5 should be eliminated) - something like inner join
I would like to avoid creating new destinationList with updated entries because both lists already exist and are very large,
so no "convert" or "select new".
In the end destinationList should contain:
1 "1111"
2 "2222"
3 "3333"
Is there some kind of elegant (one line Lambda? ;) solution to this using LINQ ?
Any help will be greatly appreciated! Thanks!

I would just build up a dictionary and use that:
Dictionary<int, string> map = sourceList.ToDictionary(x => x.Id, x => x.Name);
foreach (var item in destinationList)
if (map.ContainsKey(item.Id))
item.Name = map[item.Id];
destinationList.RemoveAll(x=> x.Name == null);

Hope this will your desired result. First join two list based on key(Id) and then set property value from sourceList.
var result = destinationList.Join(sourceList, d => d.Id, s => s.Id, (d, s) =>
{
d.Name = s.Name;
return d;
}).ToList();

Barring the last requirement of "avoid creating new destinationList" this should work
var newList = destinationList.Join(sourceList, d => d.Id, s => s.Id, (d, s) => s);
To take care of "avoid creating new destinationList", below can be used, which is not any different than looping thru whole list, except that it probably is less verbose.
destinationList.ForEach(d => {
var si = sourceList
.Where(s => s.Id == d.Id)
.FirstOrDefault();
d.Name = si != null ? si.Name : "";
});
destinationList.RemoveAll(d => string.IsNullOrEmpty(d.Name));

Frankly, this is the simplest:
var dictionary = sourceList.ToDictionary(x => x.Id, x => x.Name);
foreach(var item in desitnationList) {
if(dictionary.ContainsKey(item.Id)) {
item.Name = dictionary[item.Id];
}
}
destinationList = destinationList.Where(x => x.Name != null).ToList();
You could do something ugly with Join but I wouldn't bother.

I hope this will be useful for you. At the end, destinationList has the correct data, without creating any new list of any kind.
destinationList.ForEach(x =>
{
SourceType newSource = sourceList.Find(s=>s.Id == x.Id);
if (newSource == null)
{
destinationList.Remove(destinationList.Find(d => d.Id == x.Id));
}
else
{
x.Name = newSource.Name;
}
});

Group By Multiple Columns

How can I do GroupBy multiple columns in LINQ
Something similar to this in SQL:
SELECT * FROM <TableName> GROUP BY <Column1>,<Column2>
How can I convert this to LINQ:
QuantityBreakdown
(
MaterialID int,
ProductID int,
Quantity float
)
INSERT INTO #QuantityBreakdown (MaterialID, ProductID, Quantity)
SELECT MaterialID, ProductID, SUM(Quantity)
FROM #Transactions
GROUP BY MaterialID, ProductID

Use an anonymous type.
Eg
group x by new { x.Column1, x.Column2 }

Procedural sample:
.GroupBy(x => new { x.Column1, x.Column2 })

Ok got this as:
var query = (from t in Transactions
group t by new {t.MaterialID, t.ProductID}
into grp
select new
{
grp.Key.MaterialID,
grp.Key.ProductID,
Quantity = grp.Sum(t => t.Quantity)
}).ToList();

For Group By Multiple Columns, Try this instead...
GroupBy(x=> new { x.Column1, x.Column2 }, (key, group) => new
{
Key1 = key.Column1,
Key2 = key.Column2,
Result = group.ToList()
});
Same way you can add Column3, Column4 etc.

Since C# 7 you can also use value tuples:
group x by (x.Column1, x.Column2)
or
.GroupBy(x => (x.Column1, x.Column2))

C# 7.1 or greater using Tuples and Inferred tuple element names (currently it works only with linq to objects and it is not supported when expression trees are required e.g. someIQueryable.GroupBy(...). Github issue):
// declarative query syntax
var result =
from x in inMemoryTable
group x by (x.Column1, x.Column2) into g
select (g.Key.Column1, g.Key.Column2, QuantitySum: g.Sum(x => x.Quantity));
// or method syntax
var result2 = inMemoryTable.GroupBy(x => (x.Column1, x.Column2))
.Select(g => (g.Key.Column1, g.Key.Column2, QuantitySum: g.Sum(x => x.Quantity)));
C# 3 or greater using anonymous types:
// declarative query syntax
var result3 =
from x in table
group x by new { x.Column1, x.Column2 } into g
select new { g.Key.Column1, g.Key.Column2, QuantitySum = g.Sum(x => x.Quantity) };
// or method syntax
var result4 = table.GroupBy(x => new { x.Column1, x.Column2 })
.Select(g =>
new { g.Key.Column1, g.Key.Column2 , QuantitySum= g.Sum(x => x.Quantity) });

You can also use a Tuple<> for a strongly-typed grouping.
from grouping in list.GroupBy(x => new Tuple<string,string,string>(x.Person.LastName,x.Person.FirstName,x.Person.MiddleName))
select new SummaryItem
{
LastName = grouping.Key.Item1,
FirstName = grouping.Key.Item2,
MiddleName = grouping.Key.Item3,
DayCount = grouping.Count(),
AmountBilled = grouping.Sum(x => x.Rate),
}

Though this question is asking about group by class properties, if you want to group by multiple columns against a ADO object (like a DataTable), you have to assign your "new" items to variables:
EnumerableRowCollection<DataRow> ClientProfiles = CurrentProfiles.AsEnumerable()
.Where(x => CheckProfileTypes.Contains(x.Field<object>(ProfileTypeField).ToString()));
// do other stuff, then check for dups...
var Dups = ClientProfiles.AsParallel()
.GroupBy(x => new { InterfaceID = x.Field<object>(InterfaceField).ToString(), ProfileType = x.Field<object>(ProfileTypeField).ToString() })
.Where(z => z.Count() > 1)
.Select(z => z);

var Results= query.GroupBy(f => new { /* add members here */ });

A thing to note is that you need to send in an object for Lambda expressions and can't use an instance for a class.
Example:
public class Key
{
public string Prop1 { get; set; }
public string Prop2 { get; set; }
}
This will compile but will generate one key per cycle.
var groupedCycles = cycles.GroupBy(x => new Key
{
Prop1 = x.Column1,
Prop2 = x.Column2
})
If you wan't to name the key properties and then retreive them you can do it like this instead. This will GroupBy correctly and give you the key properties.
var groupedCycles = cycles.GroupBy(x => new
{
Prop1 = x.Column1,
Prop2= x.Column2
})
foreach (var groupedCycle in groupedCycles)
{
var key = new Key();
key.Prop1 = groupedCycle.Key.Prop1;
key.Prop2 = groupedCycle.Key.Prop2;
}

group x by new { x.Col, x.Col}

.GroupBy(x => (x.MaterialID, x.ProductID))

.GroupBy(x => x.Column1 + " " + x.Column2)

For VB and anonymous/lambda:
query.GroupBy(Function(x) New With {Key x.Field1, Key x.Field2, Key x.FieldN })