Browse questions answered by Jon Skeet

are destructors necessary in C#?

I have a concern. I'm a first year student of computer science. Normally I'm very inquisitive in class but, not always my teacher has an answer, or not always knows the answer....

Destructors (or finalizers) are good to have in the language - but you should almost never use them. Basically you should only need them if you have a direct handle on an unmanaged resource, and not only is that incredibly rare, but using... more 4/12/2014 6:23:37 AM

Referencing an object more than once in a line

So I'm writing my version of Tetris. Here's what I'd like to do: screen[0][1].setColor(Color.RED); screen[0][1].setStatus(1); Is there a way to do this in only one line?

A few options spring to mind: Write a method in whatever class this is which knows about both the status and the color: // Implicitly sets color to red. Consider using an enum for statuses screen[0][1].setStatus(1); Write a method... more 4/12/2014 6:19:03 AM

Linq/C#: How to split List into variable length chunks based on list item information?

I am trying to split up a list of type Record in Linq into sub lists based on certain Type information. There is always one record with type "a" before and one with type "b" after...

You can't cleanly do this with normal LINQ, as far as I'm aware. The streaming operators within LINQ rely on you being able to make a decision about an item (e.g. whether or not to filter it, how to project it, how to group it) based on... more 4/11/2014 10:45:56 PM

Windows javac path env issues

I have my javac under my project directory. Lets say at C:\workspace\myworkspace\java\bin\javac what i want to do is, in ant, use that particular javac for building. so i...

Two potential problems... Firstly, it's possible that this: <exec executable="java\bin\javac"> ... is making Ant look for a file called java\bin\javac within the directory c:\workspace\myworkspace, where it doesn't exist. It's... more 4/11/2014 10:27:54 PM

Why is following Java naming conventions not required for compilation

Why is it not needed for a Java application to follow the Java naming conventions? In other words, why doesn't the Java compiler raise an error when the conventions are not...

Why is it not needed for a Java application to follow the Java naming conventions? Because they're conventions rather than rules. It would be very odd for naming conventions to be enshrined in a language specification as actual rules... more 4/11/2014 6:51:57 PM

Webservices : Cannot implicitly convert type 'System.Xml.Linq.XElement' to 'System.Xml.XmlElement'

I have a scenario where i have created a web service, which returns the first name and last name of the username passed through client(webservice consumer). but im getting an...

Well the error message seems reasonably clear - GetUserDetails is returning XElement (from LINQ to XML) rather than XmlDocument (from the older API). This shouldn't be a problem though, as basically you just need to select an element and... more 4/11/2014 12:53:58 PM

C# LINQ to objects query to change the field value based on List

I have the follwing objects objItem (id,name,qty) - list<items> objSel(selId) - list<int> objSel.selId is the selected item id of objItem. How to write...

Your pseudo-code is quite confusing, but I suspect you want something like: List<Item> items = ...; List<int> selectedIds = ...; foreach (var item in items.Where(x => !selectedIds.Contains(x.Id))) { item.Quantity = 0;... more 4/11/2014 10:07:04 AM

Where should I declare my variables?

When declaring my variables at the beginning of the class, I can't use them in a conditional statement in other methods. I tried declaring them inside the method it works but I...

There's no "one size fits all" answer here because there are different reasons for declaring variables. Static variables (declared directly within the class, with the static modifier) are class-wide, rather than specific to a single... more 4/11/2014 8:25:02 AM

Get Distinct Category Name From Class

I have a class with following structure :- public class Gallery { private string _category; public string Category { ...

If you just need the category names, you need to project from the list of galleries to a sequence of category names - and then Distinct will work: // Variable name changed to match C# conventions List<Gallery> galleryList =... more 4/11/2014 6:16:16 AM

Getting data value using date condition

I get Syntax error (missing operator) in query expression string strSql2 = "Select N_Serie,MacID from " + cmdb_ModelStock2.Text + " WHERE Date_Ajout = " + cmdb_Date2.Text; I...

The first thing to do is to stop constructing your SQL like that. If you really need to pick the table dynamically, you should make sure you use a whitelist of valid ones... but for the "where" clause you should use parameterized SQL -... more 4/11/2014 2:14:20 AM