Code Puzzler: How quickly can you figure out why this acting "weird"?
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And no, this isn't a programming question in the lounge. I started asking this question in the QA forum because it had me totally stumped. As I was filling out the "What I've tried" I had a major :doh: :doh: :doh: :doh: moment. To prove I'm not asking for help on the lounge, I posted a solution on [my blog](https://marcclifton.wordpress.com/2018/05/31/the-fix/). You'll need to use the password "fizbin" as the blog post is specifically for this lounge post and eventually I'll delete the post. It is a fun one though. Here's the code:
public class ModelDataContext : DataContext { public static ModelDataContext Context; public ModelDataContext(DbConnection conn) : base(conn) { Context = this; } } class Program { static ModelDataContext mdc = new ModelDataContext(new SqlConnection("\[some string\]")); static void CreateNewContext(DataContext context, out SqlConnection conn, out DataContext newContext) { conn = new SqlConnection(context.Connection.ConnectionString); newContext = (DataContext)Activator.CreateInstance(context.GetType(), new object\[\] { conn }); Console.WriteLine(context == newContext); } static void Main(string\[\] args) { SqlConnection conn2; DataContext newdc; CreateNewContext(ModelDataContext.Context, out conn2, out newdc); Console.WriteLine(ModelDataContext.Context == newdc); } }and the result is: False True Why is the second equality True when the first is False??? And for the bonus prize, what's a fix?
Latest Article - Building a Prototype Web-Based Diagramming Tool with SVG and Javascript Learning to code with python is like learning to swim with those little arm floaties. It gives you undeserved confidence and will eventually drown you. - DangerBunny Artificial intelligence is the only remedy for natural stupidity. - CDP1802
It took about a minute to solve. Assigning over the static for each constructor call is a WTF (as others have called out). Way too many statics in this Program, if it was rewritten to eliminate all of the statics, then the Program instance would hold a single context and the Main would look like this:
Main(...)
{
new Program().Run();
}If new instances of the "context" are really needed, then create a Copy constructor to reuse the default context settings on a new instance. Or use your favorite IOC container.
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You probably could, with a bit of thinking about it - it's obvious when you see it, but it's a stinker to spot if you didn't write the code (and probably even harder if you did if you are anything like me: I tend to see what I meant to write, rather than what I did :-O )
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OriginalGriff wrote:
I tend to see what I meant to write, rather than what I did
Yup that's me! As an answer: I haven't gone further in the thread, but at first glance the FALSE comes from comparing 2 different instances, where the TRUE result is comparing the same instance to itself? Fix: the first comparison is not necessary
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And no, this isn't a programming question in the lounge. I started asking this question in the QA forum because it had me totally stumped. As I was filling out the "What I've tried" I had a major :doh: :doh: :doh: :doh: moment. To prove I'm not asking for help on the lounge, I posted a solution on [my blog](https://marcclifton.wordpress.com/2018/05/31/the-fix/). You'll need to use the password "fizbin" as the blog post is specifically for this lounge post and eventually I'll delete the post. It is a fun one though. Here's the code:
public class ModelDataContext : DataContext { public static ModelDataContext Context; public ModelDataContext(DbConnection conn) : base(conn) { Context = this; } } class Program { static ModelDataContext mdc = new ModelDataContext(new SqlConnection("\[some string\]")); static void CreateNewContext(DataContext context, out SqlConnection conn, out DataContext newContext) { conn = new SqlConnection(context.Connection.ConnectionString); newContext = (DataContext)Activator.CreateInstance(context.GetType(), new object\[\] { conn }); Console.WriteLine(context == newContext); } static void Main(string\[\] args) { SqlConnection conn2; DataContext newdc; CreateNewContext(ModelDataContext.Context, out conn2, out newdc); Console.WriteLine(ModelDataContext.Context == newdc); } }and the result is: False True Why is the second equality True when the first is False??? And for the bonus prize, what's a fix?
Latest Article - Building a Prototype Web-Based Diagramming Tool with SVG and Javascript Learning to code with python is like learning to swim with those little arm floaties. It gives you undeserved confidence and will eventually drown you. - DangerBunny Artificial intelligence is the only remedy for natural stupidity. - CDP1802
It's the assignment of the static member from the instance constructor. HUGE no-no. If you want to make a singleton without using a DI framework, at least make the constructor private and have the static "Context" member be a property that will create a new object if one doesn't exist, and set it to a backing field. Something like this (might need to make Current a method instead of property if you need to pass constructor arguments, but you get the idea):
public class Singleton
{
private Singleton _current;public Singleton Current { get { if (\_current == null) { \_current = new Singleton(); } return \_current; } } private Singleton() { }}
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And no, this isn't a programming question in the lounge. I started asking this question in the QA forum because it had me totally stumped. As I was filling out the "What I've tried" I had a major :doh: :doh: :doh: :doh: moment. To prove I'm not asking for help on the lounge, I posted a solution on [my blog](https://marcclifton.wordpress.com/2018/05/31/the-fix/). You'll need to use the password "fizbin" as the blog post is specifically for this lounge post and eventually I'll delete the post. It is a fun one though. Here's the code:
public class ModelDataContext : DataContext { public static ModelDataContext Context; public ModelDataContext(DbConnection conn) : base(conn) { Context = this; } } class Program { static ModelDataContext mdc = new ModelDataContext(new SqlConnection("\[some string\]")); static void CreateNewContext(DataContext context, out SqlConnection conn, out DataContext newContext) { conn = new SqlConnection(context.Connection.ConnectionString); newContext = (DataContext)Activator.CreateInstance(context.GetType(), new object\[\] { conn }); Console.WriteLine(context == newContext); } static void Main(string\[\] args) { SqlConnection conn2; DataContext newdc; CreateNewContext(ModelDataContext.Context, out conn2, out newdc); Console.WriteLine(ModelDataContext.Context == newdc); } }and the result is: False True Why is the second equality True when the first is False??? And for the bonus prize, what's a fix?
Latest Article - Building a Prototype Web-Based Diagramming Tool with SVG and Javascript Learning to code with python is like learning to swim with those little arm floaties. It gives you undeserved confidence and will eventually drown you. - DangerBunny Artificial intelligence is the only remedy for natural stupidity. - CDP1802
The first 'true' you receive you explicitly cast the object on the function call to a DataContext type. The second you're comparing a ModelDataContext.Context object - which I'm not sure if it's a DataContext type - if not - then you're comparing unlike objects and the call will fail. Try explicitly casting the ModelDataContext.Context, and for overkill the newdc to a DataContext type and do the comparison that way. ie: Console.WriteLine((DataContext) ModelDataContext.Context == (DataContext) newdc);
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And no, this isn't a programming question in the lounge. I started asking this question in the QA forum because it had me totally stumped. As I was filling out the "What I've tried" I had a major :doh: :doh: :doh: :doh: moment. To prove I'm not asking for help on the lounge, I posted a solution on [my blog](https://marcclifton.wordpress.com/2018/05/31/the-fix/). You'll need to use the password "fizbin" as the blog post is specifically for this lounge post and eventually I'll delete the post. It is a fun one though. Here's the code:
public class ModelDataContext : DataContext { public static ModelDataContext Context; public ModelDataContext(DbConnection conn) : base(conn) { Context = this; } } class Program { static ModelDataContext mdc = new ModelDataContext(new SqlConnection("\[some string\]")); static void CreateNewContext(DataContext context, out SqlConnection conn, out DataContext newContext) { conn = new SqlConnection(context.Connection.ConnectionString); newContext = (DataContext)Activator.CreateInstance(context.GetType(), new object\[\] { conn }); Console.WriteLine(context == newContext); } static void Main(string\[\] args) { SqlConnection conn2; DataContext newdc; CreateNewContext(ModelDataContext.Context, out conn2, out newdc); Console.WriteLine(ModelDataContext.Context == newdc); } }and the result is: False True Why is the second equality True when the first is False??? And for the bonus prize, what's a fix?
Latest Article - Building a Prototype Web-Based Diagramming Tool with SVG and Javascript Learning to code with python is like learning to swim with those little arm floaties. It gives you undeserved confidence and will eventually drown you. - DangerBunny Artificial intelligence is the only remedy for natural stupidity. - CDP1802
It is a simple newb mistake. Basically, you have written overly complex code making it hard for you to debug. Simplify the syntax as much as possible and the symantec issues will reveal themselves ;)
