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IQueryable<> is losing its initial type after Linq Skip/Take

Can someone explain how to avoid the following situation?
I have a variable called data that is an IQueryable<>. As you can see before calling Skip/Take on it, the runtime knows of its exact type (IQueryable<...Module>).
After doing Skip/Take the variable data becomes an IQueryable< object>.
I want it to retain the original type it had before executing the Skip/Take. I do not know the exact type inside <> before a method that fills the data variable is executed. I know it afterwards and I can get the Type which I want to use in order to cast the Skip/Take back to the original type. How can I do that?
PS1: The collection has been returned by a method that returns an IQueryable< object>
PS2: Until the skip/take it behaves like an IQueryable< ...module>.

Your collection is of IQueryable<Object> prior to executing Skip and Take. You'll need to cast your collection to its exact type.

If your method returns an IQueryable<object>, that is all the code will know about. If you're sure of the type you can use an OfType<Module>() or Cast<Module>() linq call as appropriate to get them back to the type YOU expect rather than the type the code expects.
EDIT: After reading your comments more on the original post it almost sounds like your function that returns IQueryable<object> should actually be made into a generic function that returns IQueryable<T> so that you won't have this problem in the first place. This is quickly seeming more and more to be an XY problem. If this answer becomes invalid I'll remove it.

C#: return stong types from reflection

In the latest version of C#, is it possible to convert a dynamic type to a strong type, if you know the type in advance?
I'm using reflection to call a method on an object, which returns to a var:
var returnVal = context.GetType().InvokeMember(MethodName, BindingFlags.InvokeMethod, null, context, lParams.ToArray());
I can easily get the type being returned to returnVal. Is it possible to cast\convert thins to a more strongly typed version?
EDIT FOR CLARITY:
In this situation, I know the type being returned but only by string. To get the type, I have to do:
diAssemblies[k].GetType(diAssemblies[k].GetName().Name + "." + returnType)
Where returnType is the name of type being returned.
Ideally, I'd like to be able to get the result of the method invocation in to a strongly typed field.
CONTEXT
I'm loading assemblies containing .edmx files from a directory, then invoking methos on those contexts. At run time, the loader won't know what assemblies it's going to be loading. However, the person using the loader will be aware of the assemblies, methods and types.
This is to create a generic wrapper around database calls through entity framework (with stored procedures), that will be reused elsewhere.

If you don't know the Type statically, how could you use a statically typed reference? What you can do is have the returned type implement an interface you do know about statically, then cast to that interface.
So, if MyStrongType implements IMyStrongBehavior, you can cast the return value to IMyStrongBehavior and use that statically. The underlying value is already strongly typed, regardless of whether you cast it.
Alternately, you can store the return value in a dynamic variable (which will allow you to invoke known methods without an actual statically-typed interface.) The disadvantage here is that you don't get any Intellisense and any mistakes you make won't show up until runtime.

No, you can't get the advantages of a concrete type such as compile time checking and intellisense. This is because you are only actually working out what the type is at run time. It is late bound, which means that it's a job for dynamic and the DLR. You can cast it to an object that you know the actual object will inherit from (e.g. object), but you can't cast to the actual type. You might want to look into generics as an alternative if you had for example:
public T GetReturnVal<T>()
{
return (T)context.GetType().InvokeMember(MethodName, BindingFlags.InvokeMethod, null, context, lParams.ToArray());
}
You would at least be returning a concrete type to callers of type T. But this type has to be set at compile time, i.e. known in advance.
I recomend you read An Introduction to C# Generics as it does exactly what, from the context you've added, you need to do.

Declaring a LIST variable of an anonymous type in C#

I'm working with LINQ to SQL with ASP.NET 4 and C#. I've created a LINQ query that results in a new LIST (ie. ToList()). The returned LIST is of an ANONYMOUS type, because it's being created dynamically by the query. I want to be able to declare a variable at the page level in the code behind so I can use it in other functions and also on the front page using '<%= %>'.
Visual Studio tells me that the result is of an anonymous type, but gives me the classes names, for example: {CLASS1, CLASS2}.
How can I declare the variable of this anonymous type?

Anonymous types, by their very nature, can't be explicitly "declared". They're anonymous, unknown; you don't have a type to declare. As such, anonymous types, whether directly or as a generic type parameter, cannot be specified as parameters, used as a return type, or stored to any explicitly typed variable. You must use var to assign them, and that means you're pretty much limited to using the type in local scope.
Your only option, basically, is to convert your anonymous type into a collected type that can be explicitly declared (i.e. you must declare the type itself). Just create a simple DTO class, and before calling ToList, run the anonymous type through a Select() Linq node that uses the anonymous type to initialize your strong class.
If you are using .NET 4.0, you COULD go dynamic. The dynamic keyword, and any object that's been passed through a parameter or return type declared dynamic, basically tells the compiler not to try to verify any operation performed on it; you can try to use any operator, call any method, etc. HOWEVER, if the operator, member, or whatever other operation you are performing isn't valid for what the object actually is behind the scenes, you'll get runtime exceptions which you must handle very robustly. For this reason, the dynamic feature of .NET 4.0 is not to be used lightly.
The only other thing you can do, as Kratz said, is return an ArrayList, or an Object[] array, and use reflection to discover the anonymous type's structure. It's a no-no pretty much any way you slice it; you lose the strong typing of the collection, your code bloats considerably as you need several lines of code to perform even the simplest get or set operations, and reflection, again by its nature, can be up to 100x slower than the equivalent operation on a known static type.

You'll have to declare a type for the result, since there is no way I know of to outright declare an instance of an anonymous type. Even if you store it in a value, you would not be able to use it outside the scope where it was created.
You possible could use reflection to get at the values and just declare the variable as type IList, but that would be much more work than just creating a new type.

You could do a List<Object> and in your code you can test the type like :
if(myList[index].GetType() == typeof(Class1))
{
//put your code for class1
}
else if(myList[index].GetType() == typeof(Class2))
{
//put your code for class2
}

Reasons to specify generic types in LINQ extension methods

Just out of curiosity:
Many LINQ extension methods exist as both generic and non-generic variants, for example Any and Any<>, Where and Where<> etc. Writing my queries I usually use the non-generic variants and it works fine.
What would be the cases when one has to use generic methods?
--- edit ---
P.S.: I am aware of the fact that internally only generic methods are called and the compiler tries to resolve the content of the generic brackets <> during compilation.
My question is rather what are the cases then one has to provide the type explicitly and not to rely on the compiler's intuition?

Always. The C# compiler is smart enough to infer what the type of the method is based on the parameters. This is important when the type is anonymous, and thus has no name.
obj.SomeMethod(123); //these calls are the same
obj.SomeMethod<int>(123);
obj.SomeMethod(new { foo = 123 }); //what type would I write here?!
Edit: To be clear, you are always calling the generic method. It just looks like a non-generic method, since the compiler and Intellisense are smart.
Edit: To your updated question, you would want to be specific if you want to use a type that is not the type of the object you are passing. There are two such cases:
If the parameter implements an interface, and you want to operate on that interface, not the concrete type, then you should specify the interface:
obj.DoSomething<IEnumerable<Foo>>( new List<Foo>() );
If the parameter is implicitly convertible to another type, and you want to use the second type, then you should specify it:
obj.DoSomethingElse<long> ( 123 ); //123 is actually an int, but convertible to long
On the other hand, if you need a cast to do the conversion (or you insert one anyway), then you don't need to specify:
obj.DoYetAnotherThing( (Transformed)new MyThing() ); // calls DoYetAnotherThing<Transformed>

One example I ran into today:
ObjectSet<User> users = context.Users;
var usersThatMatch = criteria.Aggregate(users, (u, c) => u.Where(c));
The above code won't work because the .Where method doesn't return an ObjectSet<User>. You could get around this one of two ways. I could call .AsQueryable() on users, to make sure it's strongly typed as an IQueryable, or I could pass specific type arguments into the Aggregate method:
criteria.Aggregate<Func<User, bool>, IEnumerable<User>>(
PersonSet, (u, c) => u.Where(c));
Another couple of more common examples are the Cast and OfType methods, which have no way to infer what type you want, and in many cases are being called on a non-generic collection in the first place.
In general, the folks that designed the LINQ methods went out of their way to avoid the need to use explicit types in these generic methods, and for the most part you don't need to. I'd say it's best to know it's an option, but avoid doing it unless you find it necessary.

Anonymous Types

I have a Dictionary(TKey, TValue) like
Dictionary<int, ArrayList> Deduction_Employees =
new Dictionary<int, ArrayList>();
and later I add to that array list an anonymous type like this
var day_and_type = new {
TheDay = myDay,
EntranceOrExit = isEntranceDelay
};
Deduction_Employees[Employee_ID].Add(day_and_type);
Now how can I unbox that var and access those properties ??

First, you aren't unboxing the type. Anonymous types are reference types, not structures.
Even though you can technically create instances of the same type outside of the method they were declared in (as per section 7.5.10.6 of the C# 3.0 Language Specification, which states:
Within the same program, two anonymous
object initializers that specify a
sequence of properties of the same
names and compile-time types in the
same order will produce instances of
the same anonymous type.
) you have no way of getting the name of the type, which you need in order to perform the cast from Object back to the type you created. You would have to resort to a cast-by-example solution which is inherently flawed.
Cast-by-example is flawed because from a design standpoint, every single place you want to access the type outside the function it is declared (and still inside the same module), you have to effectively declare the type all over again.
It's a duplication of effort that leads to sloppy design and implementation.
If you are using .NET 4.0, then you could place the object instance in a dynamic variable. However, the major drawback is the lack of compile-time verification of member access. You could easily misspell the name of the member, and then you have a run-time error instead of a compile-time error.
Ultimately, if you find the need to use an anonymous type outside the method it is declared in, then the only good solution is to create a concrete type and substitute the anonymous type for the concrete type.

There are several ways.
Since the comments seems to indicate that I suggest you do this, let me make it clear: You should be creating a named type for your object since you intend to pass it around.
First, you can use Reflection, which another answer here has already pointed out.
Another way, which tricks .NET into giving you the right type is known as "cast by example", and it goes something like this: You need to pass your object through a generic method call, which will return the object as the right type, by inferring the right type to return.
For instance, try this:
private static T CastByExample<T>(T example, object value)
{
return (T)value;
}
and to use it:
var x = CastByExample(new { TheDay = ??, EntranceOrExit = ?? }, obj);
for the two ?? spots, you just need to pass something fitting the data type for those properties, the values will not be used.
This exploits the fact that multiple anonymous types containing the exact same properties, of the same type, in the same order, in the same assembly, will map to the same single type.
However, by this time you should be creating a named type instead.

An anonymous type has method scope. To pass an anonymous type, or a collection that contains anonymous types, outside a method boundary, you must first cast the type to object. However, this defeats the strong typing of the anonymous type. If you must store your query results or pass them outside the method boundary, consider using an ordinary named struct or class instead of an anonymous type.
Source: http://msdn.microsoft.com/en-us/library/bb397696.aspx

No you can't. You can only access the properties by using reflection. The compiler has no way of knowing what the type was, and since it's an anonymous type, you can't cast it either.

If you are using .NET 1.x - 3.x, you must use reflection.
If you use .NET 4.0, you could use a dynamic type and call the expected properties.
In neither case do you need to unbox; that's for value types. Anonymous types are always reference types.