Browse questions answered by Jon Skeet

check if collection of objects where each contain another collection of objects contain all values of List<string> via LINQ

I have a collection of objects where each object contains another collection of objects. I need to find out the fastest way to check if it contains all values of...

With your current code, you logically want: IEnumerable<Video> result = from vid in videos where selectedTags.All(tag => vid.Tags.Any(t => t.Name == tag)) ... more 3/26/2014 3:53:44 PM

Why arrays needs dimension set at define time?

I am just wondering, why can't we just define something like this: int[] arr = new int[]; arr[0] = 1; Like a list, to resize automatically. What i want to know is why is this...

List<T>'s resizing is based on creating a new array behind the scenes when it needs to. Think about what the underlying implementation looks like here. When you allocate an array, it reserves a chunk of memory, and the reference... more 3/26/2014 9:26:38 AM

Correct API approach for long processing time

I am making an HTTP web API that's mainly fed by a database. Simplified, the db contains userobjects. These objects have a last_online (when the user was online) and last_checked...

One fairly "old-school" way of handling this would be to return a continuation token - basically a job ID saying, "Check this periodically; sooner or later it'll come back with a result." Given that even 30 seconds is quite a long time,... more 3/26/2014 8:49:43 AM

Settings file types converting

I would like to save the user radio- button preference in the Settings file. Therefore, I have created a setting property called radioButtonIsChecked boolean typed. ...

Assuming the retrieved value will be of the right type, just cast it: radioButton.Checked = (bool) Properties.Settings.Default[radioButton.Name + "IsChecked"]; more 3/25/2014 12:21:32 PM

Error in DateTime insertion

I have encountered below mentioned problem while trying to enter DateTime programatically using c#. ERROR MESSAGE: The conversion of a nvarchar data type to a datetime data...

This is the problem: SqlParameter pa2 = new SqlParameter("@DTime", DbType.DateTime); pa2.Value = DateTime.Now.ToString(); You've said the parameter is a DateTime, but then you're converting it to a string - and quite possibly doing so... more 3/25/2014 11:17:41 AM

Cannot find symbol variable java

I am trying to do the following program in Java where I'm writing a recursive and an iterative method to compute the sum of all odd numbers from n to m import...

This method is the problem: public static int recursivesum(int n, int m) { if (n < m) { int s = n; // Variable declared here... scoped to the if s += recursivesum(n+2, m); } else { if (m < n) { ... more 3/25/2014 9:38:23 AM

Class Inside Method

public class Demo { public void met(Object d) { class my { public String Work(String s){ return s+",JAVA"; } } ...

can I create object of my class from main method and How? No. Only the met method knows anything about the class. If you want to use the class outside that method, you should declare it either as a nested class within Demo, or as a... more 3/25/2014 8:03:35 AM

Difference between creating an object within the constructor vs outside of the constructor?

Within my program, I am trying to create a toolbar within a frame. Within the toolbar, I have three buttons that are represented with a picture instead of text. The problem is...

In the first case, you just have three local variables declared in the constructor. In the second case, your Tool class has three fields. You can then refer to those fields in other methods, and they are part of the state of the... more 3/24/2014 6:54:30 PM

What does it mean to call a function without being bound to an identifier

I understand Lambda expressions in the sense of: delegate int del(int i); static void Main() { del myDelegate = x => x * x; int j = myDelegate(2); ...

() => is the start of a lambda expression that doesn't have any parameters. It's important to understand that a lambda expression can't exist in a vacuum - it's always part of a conversion to either a delegate type or an expression tree... more 3/24/2014 5:12:11 PM

Is there a difference between cast and strong type assignment?

I sort of ran into this today when writing some code. Take the following as an example: long valueCast = (long)(10 + intVariable); long valueTyped = 10L + intVariable; Is...

Yes, there's a big difference between those two. Not for those particular values, but the exact same expression with different values will show the difference. In the first version, the addition is done in 32-bit arithmetic, and then the... more 3/24/2014 2:57:43 PM