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Controlling LINQ query order based on other list of integers

I'm doing a LINQ query where I select the video info from table Videos. The query selects only those videos whose IDs are present in the following list:
List<int> results; //Has some values
var query = from l in dataContext.Videos
where results.Contains(l.ID)
select l;
Now how do I order the items(Video infos) in the query such the their IDs follow the same order as the List results?
I am able to do this as:
List<int> results; //Has some values
var query = from k in results
from l in dataContext.Videos
where k==l.ID
select l;
But this is slow, I need something faster.

Use a join, it's much faster
var orderedByIDList = from k in results
join l in dataContext.Videos
on k equals l.Id
select l;
Addon/Edit due to #MarcinJuraszek and #Phil comments, thanks guys.
Basically grab your data first, then sort so here's what I got:
var myList = (from l in dataContext.Videos
where results.Contains(l.ID)
select l).ToList(); //grab data and resolve to list or array
var orderedByIDList = from k in results
join l in myList
on k equals l.Id
select l; //result type IEnumerable<Video>

Here's my alternative attempt (probably not as fast as a join), which retrieves the minimum set of rows and then orders the data locally.
var results = new List<int>{ 9, 2, 3, 6, 8 };
// record the original order
var results2 = results.Select ((r, index) => new {r, index});
// get results and convert to list
var videos = dataContext.Videos.Where(v => results.Contains(v.Id)).ToList();
// order according to results order
var ordered = videos.Select (v =>
new {v, results2.Single (r => r.r == v.Id).index})
.OrderBy (v => v.index).Select (v => v.v)

Remove items from list that exist in another list

Both the following lists contain a QuoteID field. What is the best way to eliminate items from the currentQuotes list that have a QuoteID that exists in the quoteData list? Thanks.
//Establish - Instantiate lists
IList<QuotePaneView> currentQuotes = new List<QuotePaneView>();
IList<Quote> quoteData = new List<Quote>();
//Fill lists
currentQuotes = theQuotePaneService.GetAllQuotePanelStuff();
quoteData = theQuoteDataService.GetAllQuoteData();

A simple piece of Linq can help here:
Consider the following:
var list1 = new List<int>();
list1.Add(1);
list1.Add(3);
list1.Add(5);
var list2 = new List<int>();
list2.Add(1);
list2.Add(2);
list2.Add(3);
var diff = list1.Except(list2);

You can use Except to get the set difference based on the ID. Then you only have to join the result(the unique ID's that are not in quoteData) to the currentQuotes list.
var notInQuoteData = currentQuotes.Select(q => q.QuoteID).Except(quoteData.Select(q => q.QuoteID));
var result = (from qUnique in notInQuoteData
join q in currentQuotes on qUnique equals q.QuoteID
select q).ToList();

Get records which do not start with an alphabetical character in linq

I need to get a list of records that do not start with an alphabetical character, i.e. which either starts with a numerical character or any special character.
Whats the simple LINQ query to get this list?

List<string> Entries = new List<string>();
Entries.Add("foo");
Entries.Add("bar");
Entries.Add("#foo");
Entries.Add("1bar");
var NonAlphas = (from n in Entries
where !char.IsLetter(n.ToCharArray().First())
select n);
For Linq-to-sql you could hydrate your retrieval from the database by by enumerating the query (call ToList). From that point on, your operations will be against in-memory objects and those operations will not be translated into SQL.
List<string> Entries = dbContext.Entry.Where(n => n.EntryName).ToList();
var NonAlphas = Entries.Where(n => !char.IsLetter(n.First()));

Something like this?
List<string> lst = new List<string>();
lst.Add("first");
lst.Add("second");
lst.Add("third");
lst.Add("2abc");
var result = from i in lst where !char.IsLetter(i[0]) select i;
List<string> output = result.ToList();
Edit: I realized that using Regex here was overkill and my solution wasn't perfect anyway.

string[] x = new string[3];
x[0] = "avb";
x[1] = "31df";
x[2] = "%dfg";
var linq = from s in x where !char.IsLetter(s.ToString().First()) select s;
List<string> simplelist = new List<string>(linq);
/* in simple list you have only "31df" & "dfg" */

One thing to note is that you don't need to convert the string to a chararray to use linq on it.
The more consise version would be:
var list = new List<string> {"first","third","second","2abc"};
var result = list.Where(word => !char.IsLetter(word.First()));

Working on lambda expression

I am squaring each integer in a List. Here is the code.
class SomeIntgs
{
List<int> newList = new List<int>();
public List<int> get()
{
IEnumerable<int> intrs = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 };
newList.AddRange(intrs);
return newList;
}
}
I am getting error in Main()
SomeIntgs stg = new SomeIntgs();
var qry = from n in stg.get() where (P => P*P) select n;
Error : "Can not convert lambda expression to type bool ".
Help Please.
Also help me, how can i handle lambda in general context

You don't need the where, try this:
SomeIntgs stg = new SomeIntgs();
var qry = from n in stg.get() select n*n;
or
var qry = stg.get().Select(P => P*P);
Enumerable.Where is used to filter elements from a sequence - what you really want to do is project a new sequence of elements like I have shown above.

The lambda that the where clause takes specifies how you match an item from your IQueryable. Any member of the IQueryable that satisfies the expression you supply will be returned. (This is why your compiler is complaining about bools).
As others have mentioned, you can drop the where clause to square each item in the list.
var ints = new int []{1,2,3,4,5,6,7,8};
var squares = ints.Select(x => x*x);
var evenSquares = ints.Where(x => (x % 2) == 0).Select(x => x*x); // only square
//the even numbers in the list

SomeIntgs stg = new SomeIntgs();
var qry = from n in stg.get() select n*n;

Count occurrences of values across multiple columns

I am having a terrible time finding a solution to what I am sure is a simple problem.
I started an app with data in Lists of objects. It's pertinent objects used to look like this (very simplified):
class A {
int[] Nums;
}
and
List<A> myListOfA;
I wanted to count occurrences of values in the member array over all the List.
I found this solution somehow:
var results
from a in myListOfA
from n in a.Nums
group n by n into g
orderby g.Key
select new{ number = g.Key, Occurences = g.Count}
int NumberOfValues = results.Count();
That worked well and I was able to generate the histogram I wanted from the query.
Now I have converted to using an SQL database. The table I am using now looks like this:
MyTable {
int Value1;
int Value2;
int Value3;
int Value4;
int Value5;
int Value6;
}
I have a DataContext that maps to the DB.
I cannot figure out how to translate the previous LINQ statement to work with this. I have tried this:
MyDataContext myContext;
var results =
from d in myContext.MyTable
from n in new{ d.Value1, d.Value2, d.Value3, d.Value4, d.Value5, d.Value6 }
group n by n into g
orderby g.Key
select new { number = g.Key, Occurences = g.Count() };
I have tried some variations on the constructed array like adding .AsQueryable() at the end - something I saw somewhere else. I have tried using group to create the array of values but nothing works. I am a relative newbie when it come to database languages. I just cannot find any clue anywhere on the web. Maybe I am not asking the right question. Any help is appreciated.

I received help on a microsoft site. The problem is mixing LINQ to SQL with LINQ to Objects.
This is how the query should be stated:
var results =
from d in MyContext.MyTable.AsEnumerable()
from n in new[]{d.Value1, d.Value2, d.Value3, d.Value4, d.Value5, d.Value6}
group n by n into g
orderby g.Key
select new {number = g.Key, Occureneces = g.Count()};
Works like a charm.

If you wish to use LINQ to SQL, you could try this "hack" that I recently discovered. It isn't the prettiest most cleanest code, but at least you won't have to revert to using LINQ to Objects.
var query =
from d in MyContext.MyTable
let v1 = MyContext.MyTable.Where(dd => dd.ID == d.ID).Select(dd => dd.Value1)
let v2 = MyContext.MyTable.Where(dd => dd.ID == d.ID).Select(dd => dd.Value2)
// ...
let v6 = MyContext.MyTable.Where(dd => dd.ID == d.ID).Select(dd => dd.Value6)
from n in v1.Concat(v2).Concat(v3).Concat(v4).Concat(v5).Concat(v6)
group 1 by n into g
orderby g.Key
select new
{
number = g.Key,
Occureneces = g.Count(),
};

How about creating your int array on the fly?
var results =
from d in myContext.MyTable
from n in new int[] { d.Value1, d.Value2, d.Value3, d.Value4, d.Value5, d.Value6 }
group n by n into g
orderby g.Key
select new { number = g.Key, Occurences = g.Count() };

In a relational database, such as SQL Server, collections are represented as tables. So you should actually have two tables - Samples and Values. The Keys table would represent a single "A" object, while the Values table would represent each element in A.Nums, with a foreign key pointing to the one of the records in the Samples table. LINQ to SQL
's O/R mapper will then create a "Values" property for each Sample object, which contains a queryable collection of the attached Values. You would then use the following query:
var results =
from sample in myContext.Samples
from value in sample.Values
group value by value into values
orderby values.Key
select new { Value = values.Key, Frequency = values.Count() };