linq-to-objects

Look the code below. I'd like to replace USERNAME by the field name received in the parameter field . This method must be able to make some search on several fields. Thank, public void Searching(string field, string stringToSearch) { var res = from user in _dataContext.USERs where user.USERNAME.Contains(stringToSearch) select new { Id = user.ID, Username = user.USERNAME }; } You need to forget about the anonymous type, maybe use Tuple<int,string> instead; but: how about: IQueryable<Foo> source = // YOUR SOURCE HERE // in-memory dummy example: // source = new[] { // new Foo {Id = 1, Bar = "abc"

Is it possible to write a query where we get all those characters that could be parsed into int from any given string? For example we have a string like: "$%^DDFG 6 7 23 1" Result must be "67231" And even slight harder: Can we get only first three numbers? This will give you your string string result = new String("y0urstr1ngW1thNumb3rs". Where(x => Char.IsDigit(x)).ToArray()); And for the first 3 chars use .Take(3) before ToArray() The following should work. var myString = "$%^DDFG 6 7 23 1"; //note that this is still an IEnumerable object and will need // conversion to int, or whatever type

Here is the data that I would like to group. Start End 2 4 26 30 5 9 20 24 18 19 Because I have 18 - 19 and 20 - 24. I would add these two together as 18 - 24. In this case the rule is (a, b) => b.start - a.end = 1 and the result would be Start End 18 24 2 9 26 30 EDIT added last result row per comments below. So we'll start with a helper method called GroupWhile . It will be provided with a predicate accepting two items from the sequence, the previous and the current. If that predicate returns true, the current item goes into the same group as the previous item. If not, it starts a new group.

When solving an interview question Question A six digit number need to be found in such a manner when it is multiplied by an integer between 2 and 9 gives the original six digit number when its digits are reversed. Example: Suppose I multiply 219978 * 4 i get 879912 ,when reverse 879912 I will get 219978 back. I solved it using for (long l = 100000; l < 999999; l++) { var num = l.ToString(); for (int i = 3; i < 9; i++) { var mul = l * i; string str = mul.ToString(); char[] splitDigits = str.ToCharArray(); string reversedDigit = new string(splitDigits.Reverse().ToArray()); if (reversedDigit

Is there an equivalent of a SQL IN statement in LINQ to objects? Yes - Contains . var desiredNames = new[] { "Jon", "Marc" }; var people = new[] { new { FirstName="Jon", Surname="Skeet" }, new { FirstName="Marc", Surname="Gravell" }, new { FirstName="Jeff", Surname="Atwood" } }; var matches = people.Where(person => desiredNames.Contains(person.FirstName)); foreach (var person in matches) { Console.WriteLine(person); } (In LINQ to SQL this ends up as an "IN" query.) Note that in LINQ to Objects the above isn't really very efficient. You'd be better off with a join: var matches = from person in

I have an IQueryable whose Entity Framework 4 objects I would like to project to their DTO equivalents. One such object 'Person' is an EF4 class, and the corresponding POCO PersonP is a class I've defined. I am using Automapper to map between them. However, when I try the following code: IQueryable<Person> originalModel = _repo.QueryAll(); IQueryable<PersonP> projection = originalModel.Select(e => Mapper.Map<Person, PersonP>(e)); The projection generates this error at runtime: LINQ to Entities does not recognize the method 'TestSite.Models.PersonP Map[Person,PersonP](TestSite.DataLayer.Model

In many cases, I want to do some filtering (and sometimes projection) on the server side and then switch to client-side for operations that the LINQ provider doesn't natively support. The naive approach (which is basically what I do now) is to just break it up into multiple queries, similar to: var fromServer = from t in context.Table where t.Col1 = 123 where t.Col2 = "blah" select t; var clientSide = from t in fromServer.AsEnumerable() where t.Col3.Split('/').Last() == "whatever" select t.Col4; However, there are many times where this is more code/trouble than it's really worth. I'd really