Browse questions answered by Jon Skeet

LINQ Statement that parses multiple collection and gets a single List

I would like to know if there is a better/faster way to write the following LINQ Statement. First let me show you my class definition: public class FooA { public...

Well, in terms of efficiency that's creating a lot of extra objects for the sake of transparent identifiers in the translation from query expressions to SelectMany calls. You could convert it to: var fooDs = ListFooA.SelectMany(a =>... more 2/25/2014 11:46:18 AM

List thread safe?

Can the following be considered thread safe due to the atomic operation appearance of the code. My main concern is if the lists needs to be re-sized it becomes non-thread safe...

No. List<T> is explicitly documented not to be thread-safe: It is safe to perform multiple read operations on a List, but issues can occur if the collection is modified while it’s being read. To ensure thread safety, lock the... more 2/25/2014 10:41:31 AM

Multiple iterations of random double numbers tend to get smaller

I am creating a stock trading simulator where the last days's trade price is taken as opening price and simulated through out the current day. For that I am generating random...

Firstly, calling Thread.Sleep like this is not a good way of getting a different seed. It would be better to use a single instance of Random per thread. See my article on randomness for some suggested approaches. However, your code is... more 2/25/2014 10:37:09 AM

How does different spacing affect the unary operator?

Can anyone explain me how different spacing affects the unary operator? int i = 1; int j = i+ + +i; // this will print j=2 int k = i++ +i; // this will print k=3 int l = i+++i;...

First, let's separate this into three separate cases which can't interact: int i = 1; System.out.println(i+ + +i); // 2 int j = 1; System.out.println(j++ +j); // 3 int k = 1; System.out.println(k+++k); // 3 Now let's rewrite them... more 2/25/2014 9:43:21 AM

SqlCeCommand Parameters not working

I have a SQL Server Compact database and I'm trying to insert a record into it using cmd.ExecuteNonQuery(). This method worked perfectly fine in another project, but it doesn't...

Two problems: Firstly, your SQL is specifying literal values because of the quotes. It should be: INSERT INTO Profiles (ProfileName, ProfilePath, ProfileDescription) VALUES (@name, @path, @desc) That way the SQL refers to the... more 2/25/2014 9:01:27 AM

Linq query correct way

I want a list of people who share the same first Name, but have birth year either before 1960 or after 1970. It is just a practice query, i was working with intersect, through...

I suspect you just need to reverse your where and group by clauses. Filter first, then group: var result = from contact in contacts where contact.DateOfBirth.Year > 1970 || contact.DateOfBirth.Year <... more 2/25/2014 8:12:49 AM

Get local time for a user

I have an application in VC++ which is used by different users in different timezones. I have to convert this logic to C# now. I am struck up with the dateformats respective to...

I will have the offset for each user That's broken to start with. You can't have an offset for each user, because offsets change over time - and they don't all change at the same time. Your current code assumes that all users will... more 2/25/2014 8:05:51 AM

size is not compared when input taken from a text file

I've the below code. import java.io.File; import java.math.BigInteger; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import...

This is the problem: ArrayList<BigInteger> a=new ArrayList<BigInteger>(); ArrayList<BigInteger> b=new ArrayList<BigInteger>(); for(int j=0;j<2;j++){ // Stuff } You're reusing the same lists for each test... more 2/25/2014 7:53:28 AM

What's the access modifier of the default constructor in java?

We all know that if we don't specifically define a constructor, the compiler inserts an invisible zero-parameter constructor. I thought its access modifier was public, but in...

I thought its access modifier is public, but when I deal with a inner class issue, I found maybe I was wrong. Yup. Indeed, I found myself in the same situation a couple of years ago. I was surprised by an error (through Guice... more 2/25/2014 7:16:26 AM

VB.NET Listen for TCP connections without wasting processor usage

I am creating a voice server with VB.NET using TCPListener. To check for incoming connections I have created an infinite loop in Form Load method and whenever a connection is...

Any time you find yourself reaching for Application.DoEvents, you should try to reconsider - it's generally a workaround. At least this time you already know you're in a bad situation :) If you're happy to do everything synchronously, I... more 2/25/2014 7:04:20 AM