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convert trans-sql to LINQ LEFT JOIN and Where Clause

How would you convert this trans-sql to LINQ?
I've tried it with the DefaultIfEmpty() but it seems to not be working for me.
Any help is appreciated.
SELECT s.Status
FROM EducationModule M
LEFT JOIN EducationModuleStatus S ON M.CourseID = S.CourseID
AND M.ModuleID = S.ModuleID
AND S.StudentID = '1506'
WHERE M.courseid = 2
Thanks in advance.

Joining on multiple columns in Linq to SQL is a little different.
You have to take advantage of anonymous types and compose a type for the multiple columns you wish to compare against, and under the sheet this will generate the type of join you are looking for.
var abcd = from tl in db.EducationModule
join s in db.EducationModuleStatus
on new { t1.CourseID, t1.ModuleID } equals new {s.CourseID, s.ModuleID}
into tl_s
where tl.CourseID == 2 AND s.StudentID == '1506'
from s in tl_s.DefaultIfEmpty()
select new
{
Status = s.Status
};

Can we use if statement in linq for deciding to join or not?

I want to include a table in some conditions in Linq.
I am looking for sth like this:
var query = from x in context.Messages
if(x.senderID != 0)
{
join et in context.ETs on x.senderID equals et.ID
}
where x.Getter == SSN
select new { x.id, x.message}
Is this kind of approach possible or do I have to write two different linq queries and then I will combine them?

var query = from a in context.Messages
join b in context.ETs
on a.senderID equals b.ID
into temp
from b in temp.DefaultIfEmpty()
where a.Getter == SSN
select new { a.id, a.message}

Multiple table linq query?

Could you help me translate this SQL query in Linq and Lambda expression.
SELECT * FROM User
JOIN UserIdentifier ON User.id = UserIdentifier.user_fk
JOIN UserPassword ON User.id = UserPassword.user_fk
WHERE UserIdentifier.identifier_value = "key" AND UserPassword.password = "1234"
I already wrote this
var query = from u in context.Users
join ui in context.UserIdentifiers on u.id equals ui.user_fk into Joined
from j in Joined.DefaultIfEmpty()
join up in context.UserPasswords on u.id equals up.user_fk into Joined2
from ???
select new { id = u.id, identifier = j.identifier_value, password = Joined2.???}
with help of http://paragy.wordpress.com/2010/11/18/multiple-joins-with-linq-and-lambda/
I'm not a happy user of linq. Actually I don't like linq because of this kind of request. This one is simple but when you try complex request linq is a nightmare. It's even worst with dynamic request. I always have problem with linq syntax and the web doesn't really help. I don't find a correct documentation to write queries.
I guess I'm not the first one to ask this question but all the documentation I found seems wrong or doesn't help me. This is a simple query and I don't find correct help. I'm still waiting someone prove me that link is not just another POC.

You're missing a where clause.
And your SQL joins are regular INNER JOINs, so you don't need these join ... into g from x in g.DefaultIfEmpty() -> that's how you do an equivalent of LEFT OUTER JOIN.
var query = from u in context.Users
join ui in context.UserIdentifiers on u.id equals ui.user_fk
join up in context.UserPasswords on u.id equals up.user_fk
where ui.identifier_value == "key" && up.password == "1234"
select new
{
id = u.id,
identifier = ui.identifier_value,
password = up.password
};

Left Join using Linq with condition

I am trying to create a left join with a condition in my C# code. I can write it in SQL Server, but I am having problems writing it as a lambda expression. Here is a rough part of my SQL Code:
Select x.RequestId, aud.DepartmentId
From Requests x
Left Join UserDepartment ud on x.AssignedToTeam = ud.DepartmentId and ud.User = 'Joe'
I know how to write the Left Join but am unfamiliar with how or if it is possible to add the condition.

I suspect you want something like this:
var query = from request in db.Requests
join department in db.UserDepartments
.Where(dep => dep.User == "Joe")
on request.AssignedToTeam equals department.DepartmentId
into departments
from dep in departments.DefaultIfEmpty()
select new { request.RequestId,
DepartmentId = dep == null ? null : (int?) dep.DepartmentId
};
(Obviously change how you want to handle the absence of a department ID if necessary.)

Check out the MSDN article: How to: Perform Left Outer Joins (C# Programming Guide)

var request = db.View.Join(
db.UserDepartment.Where(w=>w.User=="Joe"),
a=>a.AssignedToTeam,
b=>b.DepartmentId,
(a,b)=> new {View = a, UserDepartment = b});

using Case or if statment in LINQ?

I have a LINQ query (using with EF)
I have the following LINQ query. Kindly guide me how I can use case or if statement in this query.
var selectedResults=
from InvoiceSet in Invoices
join BookedAreasSet in BookedAreas
on InvoiceSet.InvoiceID equals BookedAreasSet.InvoiceID
join AreaSet in Areas on BookedAreasSet.AreaID equals AreaSet.AreaID
select new
{
InvoiceSet.InvoiceNumber,
InvoiceSet.Amount,
InvoiceSet.TotalDiscount,
InvoiceSet.GST,
InvoiceSet.PaymentDate,
InvoiceSet.ShoppingCentreID,
BookedAreasSet.BookedAreaID,
AreaSet.Name //Here I want to use Case/ If statment based on some other column
};
Please guide.
Thanks

You can do it like this but using ternary operator ?
var selectedResults=
from InvoiceSet in Invoices
join BookedAreasSet in BookedAreas
on InvoiceSet.InvoiceID equals BookedAreasSet.InvoiceID
join AreaSet in Areas on BookedAreasSet.AreaID equals AreaSet.AreaID
select new {InvoiceSet.InvoiceNumber,InvoiceSet.Amount,InvoiceSet.TotalDiscount,InvoiceSet.GST, InvoiceSet.PaymentDate,InvoiceSet.ShoppingCentreID,BookedAreasSet.BookedAreaID,
AreaSet.Name, YourColumn = AreaSet.YourColumnName == yourVariable ? "firstResult" : "other result?"}
You can combine multiple conditions this way.
AreaSet.YourColumnName == yourVariable ? "firstResult" :
AreaSet.YourColumnName == YoursecondVariable ? "Some result" : "Some
other result"