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  • Lifetime issue of IDisposable unmanaged resources in a complex object graph?

    - by stakx
    This question is about dealing with unmanaged resources (COM interop) and making sure there won't be any resource leaks. I'd appreciate feedback on whether I seem to do things the right way. Background: Let's say I've got two classes: A class LimitedComResource which is a wrapper around a COM object (received via some API). There can only be a limited number of those COM objects, therefore my class implements the IDisposable interface which will be responsible for releasing a COM object when it's no longer needed. Objects of another type ManagedObject are temporarily created to perform some work on a LimitedComResource. They are not IDisposable. To summarize the above in a diagram, my classes might look like this: +---------------+ +--------------------+ | ManagedObject | <>------> | LimitedComResource | +---------------+ +--------------------+ | o IDisposable (I'll provide example code for these two classes in just a moment.) Question: Since my temporary ManagedObject objects are not disposable, I obviously have no control over how long they'll be around. However, in the meantime I might have Disposed the LimitedComObject that a ManagedObject is referring to. How can I make sure that a ManagedObject won't access a LimitedComResource that's no longer there? +---------------+ +--------------------+ | managedObject | <>------> | (dead object) | +---------------+ +--------------------+ I've currently implemented this with a mix of weak references and a flag in LimitedResource which signals whether an object has already been disposed. Is there any better way? Example code (what I've currently got): LimitedComResource: class LimitedComResource : IDisposable { private readonly IUnknown comObject; // <-- set in constructor ... void Dispose(bool notFromFinalizer) { if (!this.isDisposed) { Marshal.FinalReleaseComObject(comObject); } this.isDisposed = true; } internal bool isDisposed = false; } ManagedObject: class ManagedObject { private readonly WeakReference limitedComResource; // <-- set in constructor ... public void DoSomeWork() { if (!limitedComResource.IsAlive()) { throw new ObjectDisposedException(); // ^^^^^^^^^^^^^^^^^^^^^^^ // is there a more suitable exception class? } var ur = (LimitedComResource)limitedComResource.Target; if (ur.isDisposed) { throw new ObjectDisposedException(); } ... // <-- do something sensible here! } }

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  • HyperJAXB and IDREFs

    - by finrod
    I have eventually managed to fiddle HyperJAXB so that when XSD has complexType A and this has an IDREF to complexType B, then HyperJAXB will generate @OneToOne JPA annotations between the the two generated entities. However now I'm facing another problem: the XSD has complex type X that can IDREF to either complex type Y or complex type Z. In the end, I need instance of complex type X contain reference to either instance of class Y or class Z. Do you have any wild ideas how can this be done without manual alterations to the generated classes? And at the same time to make sure these entities are marshalled to a correct XML? How about using the JAXB plugin that allows generating classes so that they implement a particular interface? Could that lead anywhere?

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  • Protocol Buffers In C#: How Are Boxed Value Types Handled

    - by Greg Dean
    In the following examples: public class RowData { public object[] Values; } public class FieldData { public object Value; } I am curious as how either protobuf-net or dotnet-protobufs would handle such classes. I am more familiar with protobuf-net, so what I actually have is: [ProtoContract] public class RowData { [ProtoMember(1)] public object[] Values; } [ProtoContract] public class FieldData { [ProtoMember(1)] public object Value; } However I get an error saying "No suitable Default Object encoding found". Is there an easy way to treat these classes, that I am just not aware of? To elaborate more on the use case: This is a scaled down version of a data class used in remoting. So essentially it looks like this: FieldData data = new FieldData(); data.Value = 8; remoteObject.DoSomething(data); Note: I've omitted the ISerializable implementation for simplicity, but it is as you'd expect.

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  • What happens to date-times and booleans when using DbLinq with SQLite?

    - by DanM
    I've been thinking about using SQLite for my next project, but I'm concerned that it seems to lack proper datetime and bit data types. If I use DbLinq (or some other ORM) to generate C# classes, will the data types of the properties be "dumbed down"? Will date-time data be placed in properties of type string or double? Will boolean data be placed in properties of type int? If yes, what are the implications? I'm imaging a scenario where I need to write a whole second layer of classes with more specific data types and do a bunch of transformations and casts, but maybe it's not so bad. If you have any experience with this or a similar scenario, what are your "lessons learned"?

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  • Managing multiple .NET languages in a web application

    - by tomfanning
    I am part of a development team building a new ASP.NET 3.5 web application. Two of us are C# coders, and the other is a VB.NET coder. I know that we can mix languages on a per-project basis, and one can build classes in one language that inherit from classes written in the other language in a different project (which we are already doing), but I can see us getting into a situation where we might well end up with cyclic dependencies between our various project DLLs. Other than simply having a high number of projects (more seperation of concerns into more libraries), how have you managed this situation on your own projects? Note - I believe this question to be different enough from the only similar match I could find (this one) on the basis that we are not wanting to use different languages in order to take advantage of their specific features per se, but rather to make use of what developer resource is available to us (i.e. one dev just happens to be VB.NET only).

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  • How to get hibernate3-maven-plugin hbm2ddl to find JDBC driver?

    - by HDave
    I have a Java project I am building with Maven. I am now trying to get the hibernate3-maven-plugin to run the hbm2ddl tool to generate a schema.sql file I can use to create the database schema from my annotated domain classes. This is a JPA application that uses Hibernate as the provider. In my persistence.xml file I call out the mysql driver: <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/> When I run Maven, I see it processing all my classes, but when it goes to output the schema, I get the following error: ERROR org.hibernate.connection.DriverManagerConnectionProvider - JDBC Driver class not found: com.mysql.jdbc.Driver java.lang.ClassNotFoundException: com.mysql.jdbc.Driver I have the MySQL driver as a dependency of this module. However it seems like the hbm2ddl tool cannot find it. I would have guessed that the Maven plugin would have known to search the local Maven file repository for this driver. What gives? The relevant part of my pom.xml is this: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>hibernate3-maven-plugin</artifactId> <executions> <execution> <phase>process-classes</phase> <goals> <goal>hbm2ddl</goal> </goals> </execution> </executions> <configuration> <components> <component> <name>hbm2ddl</name> <implementation>jpaconfiguration</implementation> </component> </components> <componentProperties> <persistenceunit>my-unit</persistenceunit> </componentProperties> </configuration> </plugin>

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  • Would an ORM have any way of determining that a SQLite column contains date-times or booleans?

    - by DanM
    I've been thinking about using SQLite for my next project, but I'm concerned that it seems to lack proper datetime and bit data types. If I use DbLinq (or some other ORM) to generate C# classes, will the data types of the properties be "dumbed down"? Will date-time data be placed in properties of type string or double? Will boolean data be placed in properties of type int? If yes, what are the implications? I'm envisioning a scenario where I need to write a whole second layer of classes with more specific data types and do a bunch of transformations and casts, but maybe it's not as bad as I fear. If you have any experience with this or a similar scenario, how did you handle it?

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  • ASP.Net Layered app - Share Entity Data Model amongst layers

    - by Chris Klepeis
    How can I share the auto-generated entity data model (generated object classes) amongst all layers of my C# web app whilst only granting query access in the data layer? This uses the typical 3 layer approach: data, business, presentation. My data layer returns an IEnumerable<T> to my business layer, but I cannot return type T to the presentation layer because I do not want the presentation layer to know of the existence of the data layer - which is where the entity framework auto-generated my classes. It was recommended to have a seperate layer with just the data model, but I'm unsure how to seperate the data model from the query functionality the entity framework provides.

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  • What does Ruby have that Python doesn't, and vice versa?

    - by Lennart Regebro
    There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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  • C# xml serializer - Unable to generate a temporary class

    - by gosom
    I am trying to serialize an xml to a class with the following way: XmlSerializer ser = new XmlSerializer(typeof(PSW5ns.PSW5)); StringReader stringReader; stringReader = new StringReader(response_xml); XmlTextReader xmlReader; xmlReader = new XmlTextReader(stringReader); PSW5ns.PSW5 obj; obj = (PSW5ns.PSW5)ser.Deserialize(xmlReader); xmlReader.Close(); stringReader.Close(); the class PSW5 is generated automatically by xsd.exe using an PSW5.xsd file given to me. I have done the same for other classes and it works. Now i get the following error (during runtime) : {"Unable to generate a temporary class (result=1).\r\nerror CS0030: Cannot convert type 'PSW5ns.TAX_INF[]' to 'PSW5ns.TAX_INF'\r\nerror CS0029: Cannot implicitly convert type 'PSW5ns.TAX_INF' to 'PSW5ns.TAX_INF[]'\r\n"} I am confused because it works for other classes the same way. I would appreciate any suggestions. Thanks inadvance, Giorgos

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  • how to specify set of files to be copied in lib while creating war

    - by Jigar Shah
    This is my build target <target name="build-war" depends="build-java"> <war destfile="${dist.dir}/${std.war.file}" webxml="${resources.dir}/WEB-INF/web.xml"> <fileset dir="${jsp.dir}" /> <lib dir="${lib.dir}"/> <classes dir="${build.classes.dir}" /> </war> </target> Here for <lib> can i specify some how a fileset / pattern set ? Basically i want to copy different jar from different places. (Not in one directlry) And That fileset or patternset i want to be defined in another build file which actually imports this build file. <lib refid="${patternset.id}"/>

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  • Actionscript 3 Sprite AddChild

    - by Amy
    Im new to actionscript 3 and am a little confused about how the addchild function works. I want to draw 5 houses. each house has a roof and wall. Each wall has a door and a window. I have the following classes and this is how I grouped them class Main class House class Roof //a triangle class Wall //a rectangle class Door //a rectangle class Window //a square Im having trouble with inheritance of the classes. I cant made the wall class show up with a window and a door. Can someone point me to the right direction?

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  • graphviz segmentation fault

    - by LucaB
    Hi I'm building a graph with many nodes, around 3000. I wrote a simple python program to do the trick with graphviz, but it gives me segmentation fault and I don't know why, if the graph is too big or if i'm missing something. The code is: #!/usr/bin/env python # Import graphviz import sys sys.path.append('..') sys.path.append('/usr/lib/graphviz') import gv # Import pygraph from pygraph.classes.graph import graph from pygraph.classes.digraph import digraph from pygraph.algorithms.searching import breadth_first_search from pygraph.readwrite.dot import write # Graph creation gr = graph() file = open('nodes.dat', 'r') line = file.readline() while line: gr.add_nodes([line[0:-1]]) line = file.readline() file.close() print 'nodes finished, beginning edges' edges = open('edges_ok.dat', 'r') edge = edges.readline() while edge: gr.add_edge((edge.split()[0], edge.split()[1])) edge = edges.readline() edges.close() print 'edges finished' print 'Drawing' # Draw as PNG dot = write(gr) gvv = gv.readstring(dot) gv.layout(gvv,'dot') gv.render(gvv,'svg','graph.svg') and it crashes at the gv.layout() call. The files are somthing like: nodes: node1 node2 node3 edges_ok: node1 node2 node2 node3

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  • How to make this sub-sub-query work?

    - by Josh Weissbock
    I am trying to do this in one query. I asked a similar question a few days ago but my personal requirements have changed. I have a game type website where users can attend "classes". There are three tables in my DB. I am using MySQL. I have four tables: hl_classes (int id, int professor, varchar class, text description) hl_classes_lessons (int id, int class_id, varchar lessonTitle, varchar lexiconLink, text lessonData) hl_classes_answers (int id, int lesson_id, int student, text submit_answer, int percent) hl_classes stores all of the classes on the website. The lessons are the individual lessons for each class. A class can have infinite lessons. Each lesson is available in a specific term. hl_classes_terms stores a list of all the terms and the current term has the field active = '1'. When a user submits their answers to a lesson it is stored in hl_classes_answers. A user can only answer each lesson once. Lessons have to be answered sequentially. All users attend all "classes". What I am trying to do is grab the next lesson for each user to do in each class. When the users start they are in term 1. When they complete all 10 lessons in each class they move on to term 2. When they finish lesson 20 for each class they move on to term 3. Let's say we know the term the user is in by the PHP variable $term. So this is my query I am currently trying to massage out but it doesn't work. Specifically because of the hC.id is unknown in the WHERE clause SELECT hC.id, hC.class, (SELECT MIN(output.id) as nextLessonID FROM ( SELECT id, class_id FROM hl_classes_lessons hL WHERE hL.class_id = hC.id ORDER BY hL.id LIMIT $term,10 ) as output WHERE output.id NOT IN (SELECT lesson_id FROM hl_classes_answers WHERE student = $USER_ID)) as nextLessonID FROM hl_classes hC My logic behind this query is first to For each class; select all of the lessons in the term the current user is in. From this sort out the lessons the user has already done and grab the MINIMUM id of the lessons yet to be done. This will be the lesson the user has to do. I hope I have made my question clear enough.

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  • jQuery: Trying to write my first plugin, how can I pass a selector to my func?

    - by Jannis
    Hi, I am trying to start writing some simple jQuery plugins and for my first try if figured I would write something that does nothing else but apply .first & .last classes to passed elements. so for instance i want to ultimately be able to: $('li').firstnlast(); So that in this html structure: <ul> <li></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li></li> </ul> it would create the following: <ul> <li class="first"></li> <li></li> <li></li> <li class="last"></li> </ul> <ul> <li class="first"></li> <li class="last"></li> </ul> What i have written so far in my plugin is this: (function($) { $.fn.extend({ firstnlast: function() { $(this) .first() .addClass('first') .end() .last() .addClass('last'); } }); })(jQuery); However the above only returns this: <ul> <li class="first"></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li class="last"></li> </ul> It seems that passing only the li into the function it will look at all li elements on the entire page and then apply the classes to it. What I need to figure out is how i can basically make the function 'context aware' so that passing the above li into the function would apply the classes to those lis inside of the parent ul, not to the first and last li on the entire page. Any hints, ideas and help would be much appreciated. Thanks for reading, Jannis

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  • Cyclic References and WCF

    - by Kunal
    I have generated my POCO entities using POCO Generator, I have more than 150+ tables in my database. I am sharing POCO entities all across the application layers including the client. I have disabled both LazyLoading and ProxyCreation in my context.I am using WCF on top of my data access and business layer. Now, When I return a poco entity to my client, I get an error saying "Underlying connection was closed" I enabled WCF tracing and found the exact error : Contains cycles and cannot be serialized if reference tracking is disabled. I Looked at MSDN and found solutions like setting IsReference=true in the DataContract method atttribute but I am not decorating my POCO classes with DataContracts and I assume there is no need of it as well. I won't be calling that as a POCO if I decorate a class with DataContract attribute Then, I found solutions like applying custom attribute [CyclicReferenceAware] over my ServiceContracts.That did work but I wanted to throw this question to community to see how other people managed this and also why Microsoft didn't give built in support for figuring out cyclic references while serializing POCO classes

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  • Special kind of queue

    - by devoured elysium
    I am looking for something like a Queue that would allow me to put elements at the end of the queue and pop them out in the beggining, like a regular Queue does. The difference would be that I also need to compact the Queue from time to time. This is, let's assume I have the following items on my Queue (each character, including the dot, is an item in the Queue): e d . c . b . a (this Queue has 8 items) Then, I'd need for example to remove the last dot, so to get: e d . c . b a Is there anything like that in the Java Collection classes? I need to use this for a program I am doing where I can't use anything but Java's classes. I am not allowed to design one for myself. Currently I'm just using a LinkedList, but I thought maybe this would be more like a Queue than a LinkedList. Thanks

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  • Who pays developers of open-source software?

    - by darko petreski
    We are facing a lot of open source software. But someone needs to write that software. How are they payed? Do you know a good article about the open source politics and economy? Sometimes the big companies themselves release open source because they have some benefits. Then they sell support, advices ... My question is what is the real economy about open software? No professional will work for nothing. This software are couple of classes but thousand or may be millions of classes. If you are really a pro you will write software for money, because you have life, wife, kids, taxes, you must earn. Please do not tell me that they are doing this for pleasure or hobby!

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  • How to avoid having very large objects with Domain Driven Design

    - by Pablojim
    We are following Domain Driven Design for the implementation of a large website. However by putting the behaviour on the domain objects we are ending up with some very large classes. For example on our WebsiteUser object, we have many many methods - e.g. dealing with passwords, order history, refunds, customer segmentation. All of these methods are directly related to the user. Many of these methods delegate internally to other child object but this still results in some very large classes. I'm keen to avoid exposing lots of child objects e.g. user.getOrderHistory().getLatestOrder(). What other strategies can be used to avoid this problems?

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  • Update webreference gives troubles with different versions of dll

    - by Natrium
    In my application, I use some dll, let's say library.dll, version 1.0 In my webservice, I also use library.dll, but version 2.0 When I do an update of the webreference, the classes inside of the dll are also generated in the webreference. And this gives troubles because in my application, the classes that are defined in the dll now are also available in the reference and there is a mismatch. How can I solve this? I need to be able to tell the webservice to ignore the dll-code when updating the webreference in the one or the other way. I use Visual Studio 2008.

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  • MVC paths in Extjs

    - by Oleg
    I have got a ExtJs application (MVC). So, I define many controllers, models, views and stores. At now, the structure of my project is not easy. For example my model: Ext.define('KP.model.account.AccountList', { extend: 'Ext.data.Model', fields: ['parameter', 'string_value'] }); I define my store with model like this: Ext.define('KP.store.account.AccountList', { extend: 'Ext.data.Store', alias: 'store.s_AccountList', model: 'KP.model.account.AccountList', ...................................... }); If I want to move some .js files, I must rewrite many paths in classes definitions. So, how can I declare my classes (by alias maybe) and use them more effectively? It's need, If I move files on files tree. Thanks!

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