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• Asp.net error object not set to a reference

  - by Frank

  Hi all, Because I rush in development (a lot of whip cracking here) and declare my objects at the top of the function and instantiate inside my try-catch block, I get a lot of the good old "object not set to an instance of an object" errors while doing TDD, and later if I do miss a branch that object was used in (doing VB now, would prefer C#) or just in every day coding, object not set to an instance of an object is a bit vague. Sure the stack trace sends me to the line the error occured at, but it would be nice if I could modify my logging to either name the object or its type because sometimes I have multiple objects on the same line. It's not the end of the world, but in the end it would save me a few minutes each day. Any ideas on how I can pass the info on which object wasn't set? Thanks

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• Django check for any exists for a query

  - by Hulk

  In django how to check whether any entry exists for a query sc=scorm.objects.filter(Header__id=qp.id) This was how it was done in php if(mysql_num_rows($resultn)) { } else { }

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• Assign C++ instance method to a global-function-pointer ?

  - by umanga

  Greetings, My project structure is as follows: \- base (C static library) callbacks.h callbacks.c paint_node.c . . * libBase.a \-app (C++ application) main.cpp In C library 'base' , I have declared global-function-pointer as: in singleheader file callbacks.h #ifndef CALLBACKS_H_ #define CALLBACKS_H_ extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); #endif /* CALLBACKS_H_ */ in single C file they are initialized as callbacks.c #include "callbacks.h" void (*putPixelCallBack)(); void (*putImageCallBack)(); Other C files access this callback-functions as: paint_node.c #include "callbacks.h" void paint_node(node *node,int index){ //Call callbackfunction . . putPixelCallBack(node->x,node->y,index); } I compile these C files and generate a static library 'libBase.a' Then in C++ application, I want to assign C++ instance method to this global function-pointer: I did something like follows : in Sacm.cpp file #include "Sacm.h" extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); void Sacm::doDetection() { putPixelCallBack=(void(*)())&paintPixel; //call somefunctions in 'libBase' C library } void Sacm::paintPixel(int x,int y,int index) { qpainter.begin(this); qpainter.drawPoint(x,y); qpainter.end(); } But when compiling it gives the error: sacmtest.cpp: In member function ‘void Sacm::doDetection()’: sacmtest.cpp:113: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say ‘&Sacm::paintPixel’ sacmtest.cpp:113: error: converting from ‘void (Sacm::)(int, int, int)’ to ‘void ()()’ Any tips?

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• DataMapper: using auto_migrate! with many-to-many dependencies?

  - by pschuegr

  Hi, I'm trying to migrate my app from MySql to Postgresql, using Rails3-pre and the latest DataMapper. I have several models which are related through many-to-many relationships using :through = Resource, which means that DataMapper creates a join table with foreign keys for both models. I can't auto_migrate! these changes, because I keep getting this: ERROR: cannot drop table users because other objects depend on it DETAIL: constraint artist_users_owner_fk on table artist_users depends on table users constraint site_users_owner_fk on table site_users depends on table users HINT: Use DROP ... CASCADE to drop the dependent objects too. I have tried everything I can think of, and thought I had things working when I added :constraint = :skip to the field definition, but I keep getting that error back when I try and run auto_migrate. I thought that :skip meant that it would ignore the dependents, but maybe that only applies for deleting rows and not dropping tables? I should mention that I can run auto_migrate after i nuke the db once, but after that, errors. Any suggestions or advice much appreciated.

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• Sort/Enumerate an NSArray from somewhere in the middle?

  - by Kenny Winker

  I have an NSArray, with objects ordered like so: a b c d e f I would like to enumerate through this array in this order: c d e f a b i.e. starting at some point that is not the beginning, but hitting all the items. I imagine this is a matter of sorting first and then enumerating the array, but I'm not sure if that's the best technique... or, frankly, how to sort the array like this. Edit Adding details: These will be relatively small arrays, varying from 3 to 10 objects. No concurrent access. I'd like to permanently alter the sort order of the array each time I do this operation.

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• Help With LINQ: Mixed Joins and Specifying Default Values

  - by Corey O.

  I am trying to figure out how to do a mixed-join in LINQ with specific access to 2 LINQ objects. Here is an example of how the actual TSQL query might look: SELECT * FROM [User] AS [a] INNER JOIN [GroupUser] AS [b] ON [a].[UserID] = [b].[UserID] INNER JOIN [Group] AS [c] ON [b].[GroupID] = [c].[GroupID] LEFT JOIN [GroupEntries] AS [d] ON [a].[GroupID] = [d].[GroupID] WHERE [a].[UserID] = @UserID At the end, basically what I would like is an enumerable object full of GroupEntry objects. What am interested is the last two tables/objects in this query. I will be displaying Groups as a group header, and all of the Entries underneath their group heading. If there are no entries for a group, I still want to see that group as a header without any entries. Here's what I have so far: So from that I'd like to make a function: public void DisplayEntriesByUser(int user_id) { MyDataContext db = new MyDataContext(); IEnumberable<GroupEntries> entries = ( from user in db.Users where user.UserID == user_id join group_user in db.GroupUsers on user.UserID = group_user.UserID into a from join1 in a join group in db.Groups on join1.GroupID equals group.GroupID into b from join2 in b join entry in db.Entries.DefaultIfEmpty() on join2.GroupID equals entry.GroupID select entry ); Group last_group_id = 0; foreach(GroupEntry entry in entries) { if (last_group_id == 0 || entry.GroupID != last_group_id) { last_group_id = entry.GroupID; System.Console.WriteLine("---{0}---", entry.Group.GroupName.ToString().ToUpper()); } if (entry.EntryID) { System.Console.WriteLine(" {0}: {1}", entry.Title, entry.Text); } } } The example above does not work quite as expected. There are 2 problems that I have not been able to solve: I still seem to be getting an INNER JOIN instead of a LEFT JOIN on the last join. I am not getting any empty results, so groups without entries do not appear. I need to figure out a way so that I can fill in the default values for blank sets of entries. That is, if there is a group without an entry, I would like to have a mostly blank entry returned, except that I'd want the EntryID to be null or 0, the GroupID to be that of of the empty group that it represents, and I'd need a handle on the entry.Group object (i.e. it's parent, empty Group object). Any help on this would be greatly appreciated. Note: Table names and real-world representation were derived purely for this example, but their relations simplify what I'm trying to do.

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• Set sprite width or height without scaling it's children

  - by Gabi Barrientos

  I am trying to dynamically change the width and height of a Sprite object, which is a container for other similar Sprite objects. The container object automatically changes it's size according to the size of it's children, but when I change the position of the children objects, the size of the container stays the same and it's children appear to be placed outside of the container. I tried to solve this problem by using something like this: if (container.width < (child.x + child.width)) { container.width = (child.x + child.width); } but when I use this code, the container object's children are scaled. Is there a way to change the container's size without scaling it's children?

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• [C#] Finding the index of a queue that holds a member of a containing object for a given value

  - by Luke Mcneice

  I have a Queue that contains a collection of objects, one of these objects is a class called GlobalMarker that has a member called GlobalIndex. What I want to be able to do is find the index of the queue where the GlobalIndex contains a given value (this will always be unique). Simply using the .contains function shown bellow returns a bool. How can I obtain the queue index of this match? RealTimeBuffer.OfType<GlobalMarker>().Select(o => o.GlobalIndex).Contains(INT_VALUE);

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• Are we using IoC effectively?

  - by Juliet

  So my company uses Castle Windsor IoC container, but in a way that feels "off": All the data types are registered in code, not the config file. All data types are hard-coded to use one interface implementation. In fact, for nearly all given interfaces, there is and will only ever be one implementation. All registered data types have a default constructor, so Windsor doesn't instantiate an object graph for any registered types. The people who designed the system insist the IoC container makes the system better. We have 1200+ public classes, so its a big system, the kind where you'd expect to find a framework like Windsor. But I'm still skeptical. Is my company using IoC effectively? Is there an advantage to new'ing objects with Windsor than new'ing objects with the new keyword?

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• How to create a generic list in this wierd case in c#

  - by Marc Bettex

  Hello, In my program, I have a class A which is extended by B, C and many more classes. I have a method GetInstance() which returns a instance of B or C (or of one of the other child), but I don't know which one, so the return type of the method is A. In the method CreateGenericList(), I have a variable v of type A, which is in fact either a B, a C or another child type and I want to create a generic list of the proper type, i.e. List<B> if v is a B or List<C> if v is a C, ... Currently I do it by using reflection, which works, but this is extremely slow. I wanted to know if there is another way to to it, which doesn't use reflection. Here is an example of the code of my problem: class A { } class B : A { } class C : A { } // More childs of A. class Program { static A GetInstance() { // returns an instance of B or C } static void CreateGenericList() { A v = Program.GetInstance(); IList genericList = // Here I want an instance of List<B> or List<C> or ... depending of the real type of v, not a List<A>. } } I tried the following hack. I call the following method, hoping the type inferencer will guess the type of model, but it doesn't work and return a List<A>. I believe that because c# is statically typed, T is resolved as A and not as the real type of model at runtime. static List<T> CreateGenericListFromModel<T>(T model) where T : A { return new List<T> (); } Does anybody have a solution to that problem that doesn't use reflection or that it is impossible to solve that problem without reflection? Thank you very much, Marc

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• Choosing a design pattern for a class that might change it's internal attributes

  - by the_drow

  I have a class that holds arbitrary state and it's defined like this: class AbstractFoo { }; template <class StatePolicy> class Foo : public StatePolicy, public AbstractFoo { }; The state policy contains only protected attributes that represent the state. The state might be the same for multiple behaviors and they can be replaced at runtime. All Foo objects have the same interface to abstract the state itself and to enable storing Foo objects in containers. I would like to find the least verbose and the most maintainable way to express this.

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• Java Concurrency in practice sample question

  - by andy boot

  I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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• Mocking imported modules in Python

  - by Evgenyt

  I'm trying to implement unit tests for function that uses imported external objects. For example helpers.py is: import os import pylons def some_func(arg): ... var1 = os.path.exist(...) var2 = os.path.getmtime(...) var3 = pylons.request.environ['HTTP_HOST'] ... So when I'm creating unit test for it I do some mocking (minimock in my case) and replacing references to pylons.request and os.path: import helpers def test_some_func(): helpers.pylons.request = minimock.Mock("pylons.request") helpers.pylons.request.environ = { 'HTTP_HOST': "localhost" } helpers.os.path = minimock.Mock(....) ... some_func(...) # assert ... This does not look good for me. Is there any other better way or strategy to substitute imported function/objects in Python?

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• What is the easiest way to get the property value from a passed lambda expression in an extension me

  - by Andrew Siemer

  I am writing a dirty little extension method for HtmlHelper so that I can say something like HtmlHelper.WysiwygFor(lambda) and display the CKEditor. I have this working currently but it seems a bit more cumbersome than I would prefer. I am hoping that there is a more straight forward way of doing this. Here is what I have so far. public static MvcHtmlString WysiwygFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression) { return MvcHtmlString.Create(string.Concat("<textarea class=\"ckeditor\" cols=\"80\" id=\"", expression.MemberName(), "\" name=\"editor1\" rows=\"10\">", GetValue(helper, expression), "</textarea>")); } private static string GetValue<TModel, TProperty>(HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression) { MemberExpression body = (MemberExpression)expression.Body; string propertyName = body.Member.Name; TModel model = helper.ViewData.Model; string value = typeof(TModel).GetProperty(propertyName).GetValue(model, null).ToString(); return value; } private static string MemberName<T, V>(this Expression<Func<T, V>> expression) { var memberExpression = expression.Body as MemberExpression; if (memberExpression == null) throw new InvalidOperationException("Expression must be a member expression"); return memberExpression.Member.Name; } Thanks!

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• Webservice and ORM Framework?

  - by Sebastian

  Does anybody know a good web framework that includes an ORM mapper and allows straight forward implementation of web services? I'm looking for a framework written in PHP or C++. I'm looking for the following features (not all of them required, some will do nicely) data definition in one place used by database and web service WSDL generation XML output/JSON output boilerplate code generation So what I would like is a framework that let's me specify the objects, the web service functions on those objects and then generate everything that is required leaving me to fill the business logic (connecting the database to the web service). Anything like that out there? Background information for why I need this: I'm looking into creating a web project: the client is a rich web application that fetches all its data using AJAX. It will be completely custom made using only a low level javascript library. The server back end is supposed to serve static content and javascript (basically the rich web application) and to provide a RESTful web service API (which I would like to implement using aforementioned framework).

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• Looking for a free tool to visualize object relationships for C#

  - by vfilby

  Here is my ideal solution: a free tool that reads a .csporj or .sln and generates a pretty picture that shows all the objects and how they are related. By relationships, I don't mean inheritance but rather dependency. For example, if we have a Car object and Car has a member variable Wheel, I would like that Car depends on Wheel to be visualized in the graph. I know visual studio can do inheritance graphs, but that is only half of what I am looking for. Is what I am looking for possible? Are there any tools that do something similar? Related question for java: http://stackoverflow.com/questions/1824261/are-there-any-tools-to-visualize-the-objects-being-used-in-a-program

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• Django: order by count of a ForeignKey field?

  - by AP257

  This is almost certainly a duplicate question, in which case apologies, but I've been searching for around half an hour on SO and can't find the answer here. I'm probably using the wrong search terms, sorry. I have a User model and a Submission model. Each Submission has a ForeignKey field called user_submitted for the User who uploaded it. class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) My question is pretty simple: how can I get a list of the three users with the most Submissions? I trued creating a num_submissions method on the User model: def num_submissions(self): num_submissions = Submission.objects.filter(uploaded_by=self).count() return num_submissions and then doing: top_users = User.objects.filter(problem_user=False).order_by('num_submissions')[:3] but this fails, as do all the other things I've tried. Can I actually do it using a smart database query? Or should I just do something more hacky in the views file?

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• what is this 'map' mean..in django

  - by zjm1126

  this is the code: def create(request, form_class=MapForm, template_name="maps/create.html"): map_form = form_class(request.POST or None) if map_form.is_valid(): map = map_form.save(commit=False) and the map_form is : class MapForm(forms.ModelForm): slug = forms.SlugField(max_length=20, help_text = _("a short version of the name consisting only of letters, numbers, underscores and hyphens."), #error_message = _("This value must contain only letters, numbers, underscores and hyphens.")) ) def clean_slug(self): if Map.objects.filter(slug__iexact=self.cleaned_data["slug"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that slug.")) return self.cleaned_data["slug"].lower() def clean_name(self): if Map.objects.filter(name__iexact=self.cleaned_data["name"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that name.")) return self.cleaned_data["name"] class Meta: model = Map fields = ('name', 'slug', 'description')

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• P/Invoke declarations should not be safe-critical

  - by Bobrovsky

  My code imports following native methods: DeleteObject, GetFontData and SelectObject from gdi32.dll GetDC and ReleaseDC from user32.dll I want to run the code in full trust and medium trust environments (I am fine with exceptions being thrown when these imported methods are indirectly used in medium trust environments). When I run Code Analysis on the code I get warnings like: CA5122 P/Invoke declarations should not be safe-critical. P/Invoke method 'GdiFont.DeleteObject(IntPtr)' is marked safe-critical. Since P/Invokes may only be called by critical code, this declaration should either be marked as security critical, or have its annotation removed entirely to avoid being misleading. Could someone explain me (in layman terms) what does this warning really mean? I tried putting these imports in static SafeNativeMethods class as internal static methods but this doesn't make the warnings go away. I didn't try to put them in NativeMethods because after reading this article I am unsure that it's the right way to go because I don't want my code to be completely unusable in medium trust environments (I think this will be the consequence of moving imports to NativeMethods). Honestly, I am pretty much confused about the real meaning of the warning and consequences of different options to suppressing it. Could someone shed some light on all this? EDIT: My code target .NET 2.0 framework. Assembly is marked with [assembly: AllowPartiallyTrustedCallers] Methods are declared like this: [DllImport("gdi32")] internal static extern int DeleteObject(HANDLE hObject);

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• fluent interface program in Ruby

  - by intern

  we have made the following code and trying to run it. class Numeric def gram self end alias_method :grams, :gram def of(name) ingredient = Ingredient.new(name) ingredient.quantity=self return ingredient end end class Ingredient def initialize(n) @@name= n end def quantity=(o) @@quantity = o return @@quantity end def name return @@name end def quantity return @@quantity end end e= 42.grams.of("Test") a= Ingredient.new("Testjio") puts e.quantity a.quantity=90 puts a.quantity puts e.quantity the problem which we are facing in it is that the output of puts a.quantity puts e.quantity is same even when the objects are different. what we observed is that second object i.e 'a' is replacing the value of the first object i.e. 'e'. the output is coming out to be 42 90 90 but the output required is 42 90 42 can anyone suggest why is it happening? it is not replacing the object as object id's are different..only the values of the objects are replaced.

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• fluent interface program in Ruby

  - by intern

  we have made the following code and trying to run it. class Numeric def gram self end alias_method :grams, :gram def of(name) ingredient = Ingredient.new(name) ingredient.quantity=self return ingredient end end class Ingredient def initialize(n) @@name= n end def quantity=(o) @@quantity = o return @@quantity end def name return @@name end def quantity return @@quantity end end e= 42.grams.of("Test") a= Ingredient.new("Testjio") puts e.quantity a.quantity=90 puts a.quantity puts e.quantity the problem which we are facing in it is that the output of puts a.quantity puts e.quantity is same even when the objects are different. what we observed is that second object i.e 'a' is replacing the value of the first object i.e. 'e'. the output is coming out to be 42 90 90 but the output required is 42 90 42 can anyone suggest why is it happening? it is not replacing the object as object id's are different..only the values of the objects are replaced.

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• Reflection in unit tests for checking code coverage

  - by Gary

  Here's the scenario. I have VO (Value Objects) or DTO objects that are just containers for data. When I take those and split them apart for saving into a DB that (for lots of reasons) doesn't map to the VO's elegantly, I want to test to see if each field is successfully being created in the database and successfully read back in to rebuild the VO. Is there a way I can test that my tests cover every field in the VO? I had an idea about using reflection to iterate through the fields of the VO's as part of the solution, but maybe you guys have solved the problem before? I want this test to fail when I add fields in the VO, and don't remember to add checks for it in my tests.

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• PropertyGrid - is it customizable?

  - by serhio

  I have a project in that we have to represent some graphic objects on a usercontrol in WYSIWYG. Also is required to edit each objects properties(Color, Location, etc). I hesitate between using PropertyGrid ('direct' properties edit) and custom forms on DoubleClick ('indirect' edit). The PropertyGrid is very well but should correspond a some criteria: Only selected properties are Displayed (by e.g. if I have TextRectangle want display only Text and Location); Property names should be customizable and internationalizable (by e.g. TextRectangle Text property should be named "Company Name" or "???????? ???????????"). Now about is it possible I think the answer could be Yes, but is it reasonable to use it if we have not a lot of time. What could be quicker implemented, custom forms or Property panel?

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