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MVC - Joining multiple table using LINQ / lambda - Using EF

I am implementing a controller and I need to get all staff members which have a certain RiskTypeID, which will be selected by the user when they click on Navigation Item.
Here is how I would create the joins in SQL
SQL
Select
RTHG.RiskTypeID,
SM.FullName
From RiskTypeHasGroup RTHG
Inner join RiskGroup RG On RTHG.RiskGroupID = RG.ID
Inner join RiskGroupHasGroupMembers RGHGM ON RG.ID = RGHGM.RiskGroupID
Inner Join GroupMember GM ON RGHGM.GroupMemberID = GM.ID
Inner Join GroupMemberHasStaffMember GMHSM ON GM.ID = GMHSM.GroupMemberID
Inner Join StaffMember SM ON GMHSM.StaffMemberID = SM.ID
Where RTHG.RiskTypeID = 1
I’ve pulled back data before using Linq and lambda but only using simple expressions, I now need to be able to make a call which will bring back the same data as the sql outlined above, I’ve searched online but can’t find anything similar to my requirement.
Here is my Controller, I placed comments inside as guidance
Controller
public ActionResult ViewRiskTypes(int SelectedRiskTypeID)
{
var RiskTypes = _DBContext.RiskTypes.ToList(); // Get all of the current items held in RiskTypes tables, store them as a List in Var RiskTypes
var ViewModel = new List<RiskTypeWithDetails>(); // Create colletion which holds instances of RiskTypeWithDetails and pass them to the ViewModel
var Details = new RiskTypeWithDetails(); // Create a new instance of RiskType with details and store the instance in var Details
foreach (var RiskType in RiskTypes) // Loop through each Item held in var RiskTypes
{
Details.RiskTypes.Add(new RiskTypesItem { ID = RiskType.ID, Description = RiskType.Description }); // assign each items ID & Description to the same feilds in a new
// instance of RiskTypeItems (which is a property of RiskTypeWithDetails)
}
foreach (var RiskType in RiskTypes) // Loop through each item in RiskTypes
{
if (RiskType.ID == SelectedRiskTypeID) // Check Item ID matches SelectedRiskTypeID value
{
//var Details = new RiskTypeWithDetails();
Details.RiskTypeDescription = RiskType.Description; //assign the Risk type Descripton to RiskTypeWithDetails RiskTypeDescription Property
Details.RiskDetails = _DBContext
.RiskTypeHasGroups
//.GroupMemberTypeHasGroupMembers
.Where(r => r.RiskTypeID == SelectedRiskTypeID) // Where RiskTypeId matches Selected ID bring back following data from Db
.Select(r => new RiskDetails
{
RiskGroupDescription = r.RiskGroup.Description,
GroupMembers = r.RiskGroup.RiskGroupHasGroupMembers
.Select(v => v.GroupMember).ToList(),
//StaffMembers = r.RiskGroup.RiskTypeHasGroups
// .Join(r.RiskGroup.RiskTypeHasGroups,
// a => a.RiskGroupID , b => b.RiskGroup.ID,
// (a, b) => new {a, b})
// .Join(r.RiskGroup.RiskGroupHasGroupMembers,
// c => c.) // Dosent join as I would expect... no idea what to do here
}).ToList();
ViewModel.Add(Details); //Add all data retrieved to the ViewModel (This creates one item in the collection)
}
}
return View(ViewModel);
}
As you will see I want to get all Staff Members with a match for the selected RiskTypeID. I need some assistance in converting the above SQL to work within my controller as a lambda expression
Thanks in advance

You were on the right track with your commented out code! For starters, LINQ has two different sytaxes: query and method chain. You were using the method chain syntax and it can get really unmaintainable really quickly.
For an instance like this, query syntax is where it's at.
Here's the result:
from rhtg in _dbContext.RiskTypeHasGroup
where rhtg.RiskTypeID == 1
join rg in _dbContext.RiskGroup
on rhtg.RiskGroupID equals rg.ID
join rghgm in _dbContext.RiskGroupHasGroupMembers
on rg.ID equals rhtg.ID
join gm in _dbContext.GroupMember
on rg.ID equals gm.ID
join gmhsm in _dbContext.GroupMemberHasStaffMember
on gm.ID equals gmhsm.GroupMemberID
join sm in _dbContext.StaffMember
on gmhsm.StaffMemberID equals sm.ID
select new
{
rhtg.RiskTypeId,
sm.FullName
};
Do note, that I used .Net conventions for the different variables.
Here's some documentation on the query syntax:
https://msdn.microsoft.com/en-us/library/gg509017.aspx

You can write the exact same query in linq as follows:
var query = (from RTHG in _DBContext.RiskTypeHasGroup RTHG
join RG in _DBContext.RiskGroup on RTHG.RiskGroupID equals RG.ID
join RGHGM in _DBContext.RiskGroupHasGroupMembers on RG.ID equals RGHGM.RiskGroupID
join GM in _DBContext.GroupMember on RGHGM.GroupMemberID = GM.ID
join GMHSM in _DBContext.GroupMemberHasStaffMember on GM.ID equals GMHSM.GroupMemberID
join SM in _DBContext.StaffMember on GMHSM.StaffMemberID equals SM.ID
where RTHG.RiskTypeID == 1
select new {RTHG.RiskTypeID,SM.FullName});

Save the result of LINQ query to list

I'm trying to create handler to save the result of LINQ query to list and that what i reached to
public static List<string> Get()
{
LesamisContainer LC = new LesamisContainer();
List<string> list = (from pb in LC.PayBills
join c in LC.Customers on pb.CustomerId equals c.Id
join d in LC.Departments on pb.DepartmentId equals d.Id
select new { pb.Id, c.FullName, d.Name, pb.Discount, pb.TotalAmount, pb.Details, pb.Date, pb.CustomerId, pb.DepartmentId } into x
select x).Tolist();
return list;
}
but i got this exception
http://i60.tinypic.com/2lxu2o.png
Cannnot convert type 'System.Collections.Generic.List' to 'System.Collections.Generic.List'

You're creating an anonymous type with
select new { pb.Id, c.FullName, d.Name, pb.Discount, pb.TotalAmount, pb.Details, pb.Date, pb.CustomerId, pb.DepartmentId } into x
The select x just returns this type. To get a List<string> you would need to return on of the properties from this instead, eg: select x.FullName
That would be a pretty odd way of doing things though, and probably not what you really intend. I assume you don't actually want a List<string>.
In which case, since you're returning the result from the method it should be declared and not anonymous:
public class PayBillModel
{
public int Id {get;set;}
...
}
then
select new PayBillModel() { pb.Id, c.FullName, d.Name, pb.Discount, pb.TotalAmount, pb.Details, pb.Date, pb.CustomerId, pb.DepartmentId }
This way, you end up with a List<PayBillModel>.

You're getting multiple types. Try changing the List type to object instead of string
List<object> list = (from pb in LC.PayBills
join c in LC.Customers on pb.CustomerId equals c.Id
join d in LC.Departments on pb.DepartmentId equals d.Id
select new { pb.Id, c.FullName, d.Name, pb.Discount, pb.TotalAmount, pb.Details, pb.Date, pb.CustomerId, pb.DepartmentId } into x
select x).Tolist();
You can then browse through the list by:
foreach (object item in list)
{
if (item is pb.Id)
{
//do something
}
//or
//if (item.GetType() == typeof(PayBills)) { }
}

Manipulate two list of objects in c#

I have an objectA with an ID property and a Status property.
I have a ListA which is a collection of objectA.
I also have an objectB with an ID property and a Status property.
I have a ListB which is a collection of objectB.
I need to match listA collection with listB collection based on ID and if there is a match update the Status from ListB to ListA.
What is the best way to do this without foreach loop?
Thanks for the help.

You can use LINQ for this:
var objectsForUpdate = (from a in listA
join b in listB
on a.Id equals b.Id
select new { a, b });
foreach (var obj in objectsForUpdate)
{
obj.a.Status = obj.b.Status;
}
Note this cannot be achieved without using the foreach statement.

I had a similar scenario. I had cartProducts and productsPurchasePrices.
I used linq to join the two collections:
//join currentCart...
var p = currentCart.Rows.Join(
productsPurchasePrices, //... with productsPurchasePrices
row => row.ProductCode, //first collection key
purchasePrice => purchasePrice.Key, //second collection key
(row, purchasePrice) => new
{
productCode = row.ProductCode,
productMargin = purchasePrice.ProductMargin
});
References:
http://msdn.microsoft.com/en-us/library/bb397941.aspx
http://code.msdn.microsoft.com/LINQ-Join-Operators-dabef4e9

LINQ using dictionary in where clause

er have the following query in linq...
Whenever I try to run it I get a No comparison operator for type System.Int[] exception.
It's got something to do with the dictionary I am sure, but I don't understand why this isn't valid and was wondering if someone could explain?
// As requested... not sure it will help though.
var per = (
from p in OtherContext.tblPeriod
where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode)
select p).ToArray();
var com = (
from c in MyContext.tblService
join sce in MyContext.tblServiceExtension
on c.ServiceExtensionCode equals sce.ServiceExtensionCode
join sc in MyContext.tblServiceContract
on sce.ServiceContractCode equals sc.ContractCode
group sc by c.Period into comG
select new
{
PeriodNumber = comG.Key,
Group = comG,
}).ToArray();
var code =
(from c in com
join p in per on c.PeriodNumber equals p.PeriodNumber
select new
{
p.Code,
c.Group
}).ToArray();
var payDictionary = new Dictionary<int, int[]>();
// This is another linq query that returns an anonymous type with
// two properties, and int and an array.
code.ForEach(c => payDictionary.Add(c.Code, c.Group.Select(g => g.Code).ToArray()));
// MyContext is a LINQ to SQL DataContext
var stuff = (
from
p in MyContext.tblPaySomething
join cae in MyContext.tblSomethingElse
on p.PaymentCode equals cae.PaymentCode
join ca in MyContext.tblAnotherThing
on cae.SomeCode equals ca.SomeCode
where
// ca.ContractCode.Value in an int?, that should always have a value.
payDictionary[p.Code].Contains(ca.ContractCode.Value)
select new
{
p.Code,
p.ExtensionCode,
p.IsFlagged,
p.Narrative,
p.PayCode,
ca.BookCode,
cae.Status
}).ToList();

You won't be able to do this with a dictionary. The alternative is to join the three linq queries into one. You can do this with minimal impact to your code by not materializing the queries with ToArray. This will leave com and code as IQueryable<T> and allow for you compose other queries with them.
You will also need to use a group rather than constructing a dictionary. Something like this should work:
var per = (
from p in OtherContext.tblPeriod
where activeContractList.Select(c => c.DomainSetExtensionCode).Contains(p.DomainSetExtensionCode)
select p.PeriodNumber).ToArray(); // Leave this ToArray because it's materialized from OtherContext
var com =
from c in MyContext.tblService
join sce in MyContext.tblServiceExtension on c.ServiceExtensionCode equals sce.ServiceExtensionCode
join sc in MyContext.tblServiceContract on sce.ServiceContractCode equals sc.ContractCode
group sc by c.Period into comG
select new
{
PeriodNumber = comG.Key,
Group = comG,
}; // no ToArray
var code =
from c in com
where per.Contains(c.PeriodNumber) // have to change this line because per comes from OtherContext
select new
{
Code = c.PeriodNumber,
c.Group
}; // no ToArray
var results =
(from p in MyContext.tblPaySomething
join cae in MyContext.tblSomethingElse on p.PaymentCode equals cae.PaymentCode
join ca in MyContext.tblAnothThing on cae.SomeCode equals ca.SomeCode
join cg in MyContext.Codes.GroupBy(c => c.Code, c => c.Code) on cg.Key equals p.Code
where cg.Contains(ca.ContractCode.Value)
select new
{
p.ContractPeriodCode,
p.DomainSetExtensionCode,
p.IsFlagged,
p.Narrative,
p.PaymentCode,
ca.BookingCode,
cae.Status
})
.ToList();
Side Note: I also suggest using navigation properties where possible instead of joins. It makes it much easier to read and understand how objects are related and create complex queries.

How to get back result from a session

Work on entity frame work vs2010
After execute my linq query get a list of records ,want to put this record in session .Now from session Want to get back my record list ,what to do how to get back record from a session
Linq query
public IEnumerable GetSearchUserGroupPermissionData(int userID = 0)
{
var query = from p in this.Context.CmnPermissionGroupUsers
join q in this.Context.CmnPermissionGroups on p.PermissionGroupID equals q.PermissionGroupID
join r in this.Context.CmnPermissionGroupDocs on p.PermissionGroupID equals r.PermissionGroupID
join s in this.Context.CmnUserInfoes on p.UserID equals s.UserID
join t in this.Context.CmnDocLists on r.DocListID equals t.DocListID
//join u in this.Context.CmnModuleFormCompanies on t.ModuleID equals u.ModuleID
//join v in this.Context.CmnModuleLists on u.ModuleID equals v.ModuleID
//join w in this.Context.CmnFormLists on u.FormID equals w.FormID
where p.IsDeleted == false
select new
{
RecordID = p.PermissionGroupUserRecordID,
s.UserID,
s.UserFirstName,
q.PermissionGroupName,
p.EffectiveDate,
p.StatusID,
t.DocListID,
t.DocName,
t.ModuleID,
// v.ModuleName,
// u.FormID,
// t.FormName,
// w.FormName,
t.ParentID,
t.Sequence,
t.IsApprovalRequired,
t.CompanyCategoryID,
t.DocTypeID
//p.CreateBy,
//p.CreateOn,
//p.CreatePc,
//p.UpdateBy,
//p.UpdateOn,
//p.UpdatePc,
//p.IsDeleted,
//p.DeleteBy,
//p.DeleteOn,
//p.DeletePc,
//p.Transfer
};
return query.WhereIf(userID != 0, w => w.UserID == userID).ToList();
}
Put result in session
Session["UserPermission"] = new PermissionGroupUserController().GetSearchUserGroupPermissionData(objEntity.UserID);
Now ,want to get back the record set from session.bellow foreach syntax area as a item contain each row all properties and values but can not assign in a variable just like bellow ,why can not assign an AnonymousType variable value to a variable.
var o = Session["UserPermission"] as IEnumerable; //use casting
foreach (var area in o)
{
//int a = area.UserID;
}
Note:sabove syntax how me error
message:foreach statement cannot operate on variables of type 'object'
because 'object' does not contain a public definition for
'GetEnumerator'
If have any query please ask.

Did you try typecasting oto IEnumerable?
Apart from that, in your foreach loop, you have to use dynamic instead of var. This is required because your type is anonymous.
But i would still strongly suggest you to use normal types instead of Anonumous ones atleast for two reasons
Code reusability.
Better code readability.