Browse questions answered by Jon Skeet

Can't seem to change properties of objects in winforms C#

This is a bit of a confusing scenario. Basically, I'm trying to set a button's color when I use setter for a private variable that I store its color in. First off, I have a...

Did I do something wrong? Yes. Your setter is just fetching the existing property value: this.btn_input.BackColor = buttonColor; this._buttonColor = buttonColor; You meant to use value, which is the implicit parameter name for the... more 5/17/2017 6:13:04 PM

Cannot convert dbconnection to sqlconnection

I have created a generic method which will work with all database like sql server,mysql and oracle and execute my sql query and return datatable. private Datatable GetData(string...

Basically, when you call new SqlCommand(), that will only work with a SqlConnection. It's not going to work for MySqlConnection, or for anything from Oracle etc. SqlCommand is tightly coupled to SqlConnection. So either you need a... more 5/16/2017 12:35:05 PM

Where do Java exceptions came from?

Until now, I thought that every Java exception has to be created somewhere by a constructor, as I can create on my own, custom exceptions: throw new Exception(); But now it...

The exception being declared isn't about what that implementation can throw - it's about what that implementation or the implementation in subclasses can throw. Service is an abstract class - and so are the two direct subclasses... more 5/16/2017 11:32:09 AM

ZoneId and LocalDateTime

I am running this piece of code in Paris right now, where its 12:40, where ECT = ECT - Europe/Paris LocalDateTime creationDateTime = LocalDateTime.now(Clock.systemUTC()); ...

No, you shouldn't. You've asked for a ZonedDateTime with the same LocalDateTime that you started with, but associated with a particular time zone. From the docs for LocalDateTime.atZone: This returns a ZonedDateTime formed from this... more 5/16/2017 10:51:08 AM

Why is `this` not available in C# 6.0 Auto Property Initialization?

I have the following code class: public class Foo { public Nested Bar { get; } = new Nested(this); public class Nested { public Nested(Foo foo) { ...

Why is it so? Isn't Auto-Property Initializer actually translated into constructor code in IL? The rules for automatically implemented property initializers are the same as those for field initializers, for the same reason. Note that... more 5/15/2017 10:33:24 AM

Why does BigDecimal divide cause rounding when it should fit within the significant digits?

Why does BigDecimal divide cause rounding to happen even though the value should fit comfortably in 4 significant digits? BigDecimal realPercent = new BigDecimal(1.25, new...

From the Javadoc of divide(BigDecimal, RoundingMode): Returns a BigDecimal whose value is (this / divisor), and whose scale is this.scale() The last part is important - the scale of your initial value is 2 (the unscaled value is... more 5/15/2017 8:32:00 AM

Is there anyway to get MethodDeclarationSyntax based on InvocationExpressionSyntax in Roslyn?

I want to write code refactor by roslyn so I wrote a code like class Program { [Obsolete()] public static void A() { } static void Main(string[] args) { ...

I suspect you just want to get the semantic model, ask it for the symbol, and get the attributes: // After you've made sure that you've got an InvocationExpressionSyntax var model = await context.Document ... more 5/14/2017 6:46:34 PM

tying multiple events to one handler:a function with 2 object params

This is my handler function: protected static void textChange(object sender,Label labe1, EventArgs e) { var text = sender as TextBox; if...

Assuming you're trying to associate each text box with a different label, you'll need to write a method that constructs an EventHandler for the relevant label, e.g. public EventHandler CreateVisibilityHandler(Label label) { return... more 5/14/2017 11:38:39 AM

WPF async await

I'm trying to use async click event: private async void Button_Click(object sender, RoutedEventArgs e) { MessageBox.Show(Thread.CurrentThread.ManagedThreadId + " ...

You're explicitly starting a new task using Task.Factory.StartNew(). That's almost always going to run in a non-UI thread. The async/await way of doing this is not to start a new task on a different thread, not to use the dispatcher, and... more 5/13/2017 10:22:09 AM

Unary operator precedence in java

Now, according to this website, Unary post-increment has more precedence than Unary pre-increment. I presume it meant, that x++ is done before ++x. However, when tried with the...

I presume it meant, that x++ is done before ++x. No, it doesn't mean that. I've previously blogged about how I find viewing precedence in terms of execution order is problematic. It may well be valid in a computer-science-strict way,... more 5/12/2017 2:40:14 PM