Develop Reference

Is there any way to make right to left value assigning in linq or in any other way

The title is pretty unclear. But I couldn't find the proper words. Generally Linq works in the below syntax
MyList.Where().Select(x => {MyFunction(x);})
It is good in ordinary conditions but in some situation like in my case. I am creating a tree structure using dictionary. In this if I want to add a set
Set.Foreach(x => {(MyDict[logEvent.level][logEvent.event][logEvent.subevent][logEvent.filePath]).Add(x);});
But it would be nice if I can do like below
(MyDict[logEvent.level][logEvent.event][logEvent.subevent][logEvent.filePath]).Add(MySet.Foreach(x => {return x;}));
Is there any way possible to dothis ?

You can do it, if object stored in Dict has AddRange method which accepts IEnumerable<T>. But you should ski[ ForEach and just pass MySet:
MyDict[logEvent.level][logEvent.event][logEvent.subevent][logEvent.filePath]).AddRange(MySet);

Difficulty in Removing Items From List?

I have two lists. The first is of all students and the second is of selected students. I want if I one time select some student they will remove from the all-student list. Here is my code but it doesn't. Students won't get removed.
foreach (var li in ListSelectedStudents.ToList())
{
if (ListAllStudents.Contains(li))
{
ListAllStudents.Remove(li);
}
}

Contains will use equality to determine what is "equal", I am assuming here that your custom class hasn't provided a custom equality implementation, which means the default equatable will be provided for that type and it's just using reference equality. So even though you think two things are "equal", the Contains method doesn't and so doesn't step into the Remove call.
To get that particular code to behave what you need to do is provide an implementation of IEquatable<Student> on the Student class, as described in the remarks here.
In this instance, Contains isn't actually required as Remove will do the same checks. If there is nothing to remove, the Remove call will be transparent, effectively doing nothing.
As has been caught in the comments before I had chance to provide the information, Remove will also rely on IEquatable<Student> (docs) so you still need to provide an implementation, but it will make your code look a little cleaner:
foreach (var li in ListSelectedStudents.ToList())
{
ListAllStudents.Remove(li);
}
There may be various ways to do this without the need to implement the interface, but you won't be able to use your current code for it. I'll leave other answers to field those alternatives as it's Friday and my brain is not yet functioning properly.

have you tried using linq:
ListAllStudents.RemoveAll(m => ListSelectedStudents.Contains(m));
if it does not work, it could be something wrong with the default comparison implemented in the object, and you could either fix the comparer, or do something like:
ListAllStudents.RemoveAll(m => ListSelectedStudents.Any(n=>n.Id == m.Id)); // Assume the Id is the primary key of the object...

Try this:
ListSelectedStudents = ListSelectedStudents.Where(a => !ListSelectedStudents.Contains(a)).Select(a => a).ToList();

DbSortClause expressions must have a type that is order comparable parameter Name :Key

I am using Linq to entity and have the following query
IQueryable<DomainModel.User> userResult =
userResult.OrderBy(u => u.UserClientRoles.OrderBy(r => r.Role.RoleName));
But I am getting this error
DbSortClause expressions must have a type that is order comparable
parameter Name :Key
and it returns an empty collection.
Any idea what's going on?

.OrderBy(), when working with databases, is supposed to take in a delegate that returns only a single property that represents a column in your database. I'm not sure what you're trying to do, but it looks like
u.UserClientRoles.OrderBy(r => r.Role.RoleName)
Will return an enumeration of values, which can't be ordered.

I had the same problem, I solved it using this:
your code:
IQueryable<DomainModel.User> userResult = userResult.OrderBy(u => u.UserClientRoles.OrderBy(r => r.Role.RoleName));
my code:
List<Membership> results = new List<Membership>();
results.AddRange(memberships.OrderBy(m => m.Roles));
memberships = results.AsQueryable();
coincidences:
*.OrderBy(m => m.Roles)
solution:
*.OrderBy(m => m.Roles.Select(r => r.RoleId).FirstOrDefault())
possible problem's reason:
Maybe, you did what I did, and cause that 1 user/member could have more than 1 role in the same membership. That made a conflict with/to OrderBy() because the application can just "order" a single element at the time, when she call the Role (which is an ICollection of elements) the instead receive more than 1 element with no kind of priority's levels (even when we could assume that the application will take the role's index as priority's base level, actually its don't).
solution's explaination:
When you add the *.Select(r => r.RoleId), you are specifying to the application which element will be used to OrderBy(). But, as you shall see when you maybe reached at this point, just by using the *.Select(r => r.RoleId) could be not enough, because the application is still receiving multiple results with the same priority's level. Adding *.Select(r => r.RoleId).FirstOrDefault() you are basically saying: "...I don't care how many results you received from that element, just the focus on the first result, or order them by its default..." (default normally means EMPTY or NULL).
additional information:
I used non-official's simple concepts/meanings to explain a complex solution with simple words, which means that you could maybe have problems to find similar posts in the web by using the words/concepts used in this "answer". Otherwise, the code itself works and you shouldn't not have any problem by applying it and/or modifying it by yourself. GOOD LUCK!!! (^_^)

In my case, I was accidentally trying to order by an object instead of ordering by one of it's properties.
You should you use
var query = from Foo in Bar
orderby Foo.PropertyName
select Foo;
Instead of
var query = from Foo in Bar
orderby Foo
select Foo;
Note: you will get the same behaviour event if there is an override on Foo's ToString() method.

Issue with IQueryable<object> and List<string>

How to convert Object to List.
Can anybody tell me how to fix this issue.
This is the Error I am getting.

The problem is that your list is a List<string>, but your query returns a collection of baObject. You need to either use ToString() on this, or change your query to return a specific member.
The first option would look like:
descList.AddRange(query2.Select(ba => ba.ToString()).ToList());
The second (more likely option) could be as simple as:
descList.AddRange(query2.Select(ba => ba.Name).ToList());
(This is assuming baObject.Name is the property you want to list.)

Common problem for me in C#, is my solution good, stupid, reasonable? (Advanced Beginner)

Ok, understand that I come from Cold Fusion so I tend to think of things in a CF sort of way, and C# and CF are as different as can be in general approach.
So the problem is: I want to pull a "table" (thats how I think of it) of data from a SQL database via LINQ and then I want to do some computations on it in memory. This "table" contains 6 or 7 values of a couple different types.
Right now, my solution is that I do the LINQ query using a Generic List of a custom Type. So my example is the RelevanceTable. I pull some data out that I want to do some evaluation of the data, which first start with .Contains. It appears that .Contains wants to act on the whole list or nothing. So I can use it if I have List<string>, but if I have List<ReferenceTableEntry> where ReferenceTableEntry is my custom type, I would need to override the IEquatable and tell the compiler what exactly "Equals" means.
While this doesn't seem unreasonable, it does seem like a long way to go for a simple problem so I have this sneaking suspicion that my approach is flawed from the get go.
If I want to use LINQ and .Contains, is overriding the Interface the only way? It seems like if there way just a way to say which field to operate on. Is there another collection type besides LIST that maybe has this ability. I have started using List a lot for this and while I have looked and looked, a see some other but not necessarily superior approaches.
I'm not looking for some fine point of performance or compactness or readability, just wondering if I am using a Phillips head screwdriver in a Hex screw. If my approach is a "decent" one, but not the best of course I'd like to know a better, but just knowing that its in the ballpark would give me little "Yeah! I'm not stupid!" and I would finish at least what I am doing completely before switch to another method.
Hope I explained that well enough. Thanks for you help.

What exactly is it you want to do with the table? It isn't clear. However, the standard LINQ (-to-Objects) methods will be available on any typed collection (including List<T>), allowing any range of Where, First, Any, All, etc.
So: what is you are trying to do? If you had the table, what value(s) do you want?
As a guess (based on the Contains stuff) - do you just want:
bool x= table.Any(x=>x.Foo == foo); // or someObj.Foo
?

There are overloads for some of the methods in the List class that takes a delegate (optionally in the form of a lambda expression), that you can use to specify what field to look for.
For example, to look for the item where the Id property is 42:
ReferenceTableEntry found = theList.Find(r => r.Id == 42);
The found variable will have a reference to the first item that matches, or null if no item matched.
There are also some LINQ extensions that takes a delegate or an expression. This will do the same as the Find method:
ReferenceTableEntry found = theList.FirstOrDefault(r => r.Id == 42);

Ok, so if I'm reading this correctly you want to use the contains method. When using this with collections of objects (such as ReferenceTableEntry) you need to be careful because what you're saying is you're checking to see if the collection contains an object that IS the same as the object you're comparing against.
If you use the .Find() or .FindAll() method you can specify the criteria that you want to match on using an anonymous method.
So for example if you want to find all ReferenceTableEntry records in your list that have an Id greater than 1 you could do something like this
List<ReferenceTableEntry> listToSearch = //populate list here
var matches = listToSearch.FindAll(x => x.Id > 1);
matches will be a list of ReferenceTableEntry records that have an ID greater than 1.
having said all that, it's not completely clear that this is what you're trying to do.

Here is the LINQ query involved that creates the object I am talking about, and the problem line is:
.Where (searchWord => queryTerms.Contains(searchWord.Word))
List<queryTerm> queryTerms = MakeQueryTermList();
public static List<RelevanceTableEntry> CreateRelevanceTable(List<queryTerm> queryTerms)
{
SearchDataContext myContext = new SearchDataContext();
var productRelevance = (from pwords in myContext.SearchWordOccuranceProducts
where (myContext.SearchUniqueWords
.Where (searchWord => queryTerms.Contains(searchWord.Word))
.Select (searchWord => searchWord.Id)).Contains(pwords.WordId)
orderby pwords.WordId
select new {pwords.WordId, pwords.Weight, pwords.Position, pwords.ProductId});
}
This query returns a list of WordId's that match the submitted search string (when it was List and it was just the word, that works fine, because as an answerer mentioned before, they were the same type of objects). My custom type here is queryTerms, a List that contains WordId, ProductId, Position, and Weight. From there I go about calculating the relevance by doing various operations on the created object. Sum "Weight" by product, use position matches to bump up Weights, etc. My point for keeping this separate was that the rules for doing those operations will change, but the basic factors involved will not. I would have even rather it be MORE separate (I'm still learning, I don't want to get fancy) but the rules for local and interpreted LINQ queries seems to trip me up when I do.
Since CF has supported queries of queries forever, that's how I tend to lean. Pull the data you need from the db, then do your operations (which includes queries with Aggregate functions) on the in-memory table.
I hope that makes it more clear.