Do u find c# descent? - C# Discussion Boards

11-Apr-12 5:13

What i mean,
i keep finding out spots in c# where i think,
microsoft but why.

For example the ICollection-generic interface
which has been derived van IEnumerable and IEnumerable-generic
which let u implement the same named function only with a different return type and u think like, that can't be so how can i not implement icollection and list, dictionary etc while microsoft can.

Why is it that i need to cast a dictionary to ICollection-KeyValuePair first before i can call the dictionary's CopyTo method to get it's whole list and not just values or keys.

Or for instance when u work with an dictionary the way i do
in my latest program for my work i want copies of the retrieval
cause i need to detect chances against the dictionary.

I Used to make a getcopy function where i would pass the object
and would return a new instance filled with the data from the other.

Then when i was playing around a bit u find out that object
has MemberwiseClone only u can't access it normally.

I ended up writing the next for something which is present
on each object (should need less flags, wasn't in the mood to find out which i could skip)

private const System.Reflection.BindingFlags FullAccess = System.Reflection.BindingFlags.CreateInstance |
                                                          System.Reflection.BindingFlags.GetField |
                                                          System.Reflection.BindingFlags.GetProperty |
                                                          System.Reflection.BindingFlags.Instance |
                                                          System.Reflection.BindingFlags.InvokeMethod |
                                                          System.Reflection.BindingFlags.Public |
                                                          System.Reflection.BindingFlags.SetField |
                                                          System.Reflection.BindingFlags.SetProperty |
                                                          System.Reflection.BindingFlags.Static |
                                                          System.Reflection.BindingFlags.NonPublic;


public static T GetMemberWiseClone<T>(T ToClone)
{
    T Result = default(T);

    if (ToClone != null)
    {
        try
        {
            Result = (T)ToClone.GetType().GetMethod("MemberwiseClone", FullAccess).Invoke(ToClone, new object[] { });
        }
        catch { }
    }

    return Result;
}

All such small things just make me like, microsoft why do u hide
certain things, why do u make some things less accessible or unimplemetable
or is it just me?

BobJanova11-Apr-12 5:21

BobJanova

11-Apr-12 5:21

There's some rough edges around Collections.Generic because they had already implemented Collections (non-generic) in .Net 1 and they decided (rightly, in my view) that generic collections should play nicely with non-generic code and language constructs (e.g. foreach), so they have to implement the non-generic interfaces as well.

You can implement ICollection<T>, IEnumerable<T> etc by using explicit interface implementations for the non-generic interface.

MemberwiseClone is protected because it doesn't do what you think it does, and it's there as a piece of plumbing to make writing a proper clone method easier. Unless the target type is actually implementing MemberwiseClone to do something useful, you're introducing nasty subtle bugs by using it.

PIEBALDconsult11-Apr-12 5:41

PIEBALDconsult

11-Apr-12 5:41

There are some odd things in .net, but this isn't one of them.

You should not write a general-purpose cloner because some class hierarchies are cyclical (think of classes with parent/child relationships that refer to each other) and could cause a stack overflow.

If you have a specific class for which you want a cloner then write a specific clone method for that class.

Furthermore, swallowing the Exception in your method is nasty.

Mark Kruger11-Apr-12 6:13

11-Apr-12 6:13

The function written in my question was a 3 minute wrap, not yet formatted for my real program (which as i normally do tries to escape most errors by testing on validity before i make the call, besides that likely i'll introduce a boolean on return and the return value as an out variable)

But that about the function.
Does memberwiseclone does something different then copying fields bitwise and referenced objects by reference
?
And for the things i apply them are structures/classes which are only ment for data storage (iow abusing dictionaries for speedy retrieval of my mini in memory database like environment) i think that's more then enough.

Though if it can cause unwanted results it's handy to know that. But ain't that the same for createhandle and destroyhandle of a nativewindow etc. U need to know how to handle them and normally that would be by a good documentation of the function for everyone to read, which likely is present for memberwiseclone as well.

Eddy Vluggen11-Apr-12 7:04

Eddy Vluggen

11-Apr-12 7:04

Mark Kruger wrote:
But that about the function

MSDN[^]

Bastard Programmer from Hell Suspicious | :suss:

Mark Kruger11-Apr-12 7:38

11-Apr-12 7:38

Exactly

But still u know often when u just have enough with a shallow copy, cause u created the class/structure etc u need an not original reference instance from.
And that's exactly where i made the function for.
Just to let me not dumb re-re-re-re enter the same line of code over and over again, nor gives me need to inherit a base class which makes it public

BobJanova11-Apr-12 23:52

BobJanova

11-Apr-12 23:52

If you created the class you can provide a public Clone method which has an exactly specified interface and definition of its action.

If you are simply using an existing class, you can never know if MemberwiseClone will do what you want, because shallow copying private fields is dependent on the implementation of the class, and it is entirely legitimate for the class provider to update the private workings of the class in a way which will change how it operates.

For example, using a list: if the class you're using is simply a wrapper around an internal inner list class, you'll be getting essentially the same object after MemberwiseClone (and actions like Add will apply to both copies); if information is stored in fields of the class you're using, list modifying methods will (mostly) only apply to one copy. And you can't possibly tell which of those two it is going to be (you can use ILDASM or similar to find out what it is right now, but it might not be the same in the next release, or in the Compact Framework, or under Mono).

Mark Kruger12-Apr-12 1:29

12-Apr-12 1:29

A clear view i understand and agree with, thank you Smile | :)

Cause of the reactions yesterday ended up writing a field reader writer (including basetypes), which works on arrays and icollection(generic only) as well (and specially in those occations to make of copy of each cell) recursivly with an object array[,] to be able to detect when items and pointing to somethin' processed before in that case i place the copied variant on the spot. Implemented all real valuetypes (iow int, long, decimal, string) by individually copy lines to make sure those go well. Called my function GetDeadCopy and returns a boolean now whether it had succes or not. Have not implemented a field checker yet for combi with collection to see what's touched. But the total function does already a lot more then were i wrote the thing for. Being more easily able to use data packages in dictionaries and lists without having the need to give each package an own copy constructor (or clone however you want to name it).

Anyways thanx for the responds and the reason for me to look a bit deeper.

Re: solid edge programming

V.11-Apr-12 21:04

11-Apr-12 21:04

Please use "you" instead of "u".
thanks.

solid edge programming

issSTE11-Apr-12 3:48

issSTE

11-Apr-12 3:48

where to get tutorials or ebook. Laugh | :laugh:

Richard MacCutchan11-Apr-12 5:06

Richard MacCutchan

11-Apr-12 5:06

Have you heard of Google[^]?

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: solid edge programming

ZurdoDev11-Apr-12 8:34

ZurdoDev

11-Apr-12 8:34

It's a fad.

There are only 10 types of people in the world, those who understand binary and those who don't.

Re: solid edge programming

Richard MacCutchan11-Apr-12 21:54

Richard MacCutchan

11-Apr-12 21:54

Yeah, I wonder if it'll last?
Wink | ;)

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

find solution for deadlock

numeracy11-Apr-12 0:21

numeracy

11-Apr-12 0:21

can anybody help me in solving this deadlock?

class Program
    {
        readonly static object obj1 = new object();
        readonly static object obj2 = new object();

        static void F1()
        {
            lock (obj1)
                lock (obj2)
                {
                    Console.Write("1");
                }
        }
        static void F2()
        {
            lock (obj2)
                lock (obj1)
                {
                    Console.Write("2");
                }
        }

        static void Main(string[] args)
        {
            Task[] tasks = new[]
            {
                Task.Factory.StartNew(() => { for (int i = 0; i < 100; i++) F1(); }),
                Task.Factory.StartNew(() => { for (int i = 0; i < 100; i++) F2(); }),
            };
            Task.WaitAll(tasks);
            Console.WriteLine();
            Console.WriteLine("all done");
        }
    }

Pete O'Hanlon11-Apr-12 0:28

Pete O'Hanlon

11-Apr-12 0:28

Rather than using the locks the way you are doing it, try using Monitor.TryEnter instead. That provides a timeout that allows you to set how long it needs to wait before it gives up trying to acquire the lock.

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numeracy11-Apr-12 0:34

numeracy

11-Apr-12 0:34

can you clearly write your repaired code here?

Wes Aday11-Apr-12 0:45

Wes Aday

11-Apr-12 0:45

numeracy wrote:
write your repaired code

I am sure that he could, but why would he? Are your fingers broken?

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