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• How to customize a many-to-many inline model in django admin

  - by Jonathan

  I'm using the admin interface to view invoices and products. To make things easy, I've set the products as inline to invoices, so I will see the related products in the invoice's form. As you can see I'm using a many-to-many relationship. In models.py: class Product(models.Model): name = models.TextField() price = models.DecimalField(max_digits=10,decimal_places=2) class Invoice(models.Model): company = models.ForeignKey(Company) customer = models.ForeignKey(Customer) products = models.ManyToManyField(Product) In admin.py: class ProductInline(admin.StackedInline): model = Invoice.products.through class InvoiceAdmin(admin.ModelAdmin): inlines = [FilteredApartmentInline,] admin.site.register(Product, ProductAdmin) The problem is that django presents the products as a table of drop down menus (one per associated product). Each drop down contains all the products listed. So if I have 5000 products and 300 are associated with a certain invoice, django actually loads 300x5000 product names. Also the table is not aesthetic. How can I change it so that it'll just display the product's name in the inline table? Which form should I override, and how?

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• Reorganizing many to many relationships in Django

  - by Galen

  I have a many to many relationship in my models and i'm trying to reorganize it on one of my pages. My site has videos. On each video's page i'm trying to list the actors that are in that video with links to each time they are in the video(the links will skip to that part of the video) Here's an illustration Flash Video embedded here Actors... Ted smith: 1:25, 5:30 jon jones: 5:00, 2:00 Here are the pertinent parts of my models class Video(models.Model): actor = models.ManyToManyField( Actor, through='Actor_Video' ) # more stuff removed class Actor_Video(models.Model): actor = models.ForeignKey( Actor ) video = models.ForeignKey( Video) time = models.IntegerField() Here's what my Actor_Video table looks like, maybe it will be easier to see what im doing id actor_id video_id time (in seconds) 1 1 3 34 2 1 3 90 i feel like i have to reorganize the info in my view, but i cant figure it out. It doesn't seem to be possible in the template using djangos orm. I've tried a couple things with creating dictionaries/lists but i've had no luck. Any help is appreciated. Thanks.

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• How to save many to many fields by using an auto complete text box

  - by iHeartDucks

  If I have two models like class Author(models.Model): name = models.CharField(max_length=100) title = models.CharField(max_length=3, choices=TITLE_CHOICES) birth_date = models.DateField(blank=True, null=True) def __unicode__(self): return self.name class Book(models.Model): name = models.CharField(max_length=100) authors = models.ManyToManyField(Author) I can render the book form using a model form like this class BookForm(ModelForm): class Meta: model = Book widgets = { 'authors' : TextInput() } The authors fields is now rendered as a text box and I want to use an auto complete (where I can enter multiple authors) text box to populate the field. I am having a hard time to understand how I can save the authors in view function? I am thinking of using a hidden field to record all the author id's but I am having a hard time figuring out how to save it on the postback.

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• Add data to Django form class using modelformset_factory

  - by dean

  I have a problem where I need to display a lot of forms for detail data for a hierarchical data set. I want to display some relational fields as labels for the forms and I'm struggling with a way to do this in a more robust way. Here is the code... class Category(models.Model): name = models.CharField(max_length=160) class Item(models.Model): category = models.ForeignKey('Category') name = models.CharField(max_length=160) weight = models.IntegerField(default=0) class Meta: ordering = ('category','weight','name') class BudgetValue(models.Model): value = models.IntegerField() plan = models.ForeignKey('Plan') item = models.ForeignKey('Item') I use the modelformset_factory to create a formset of budgetvalue forms for a particular plan. What I'd like is item name and category name for each BudgetValue. When I iterate through the forms each one will be labeled properly. class BudgetValueForm(forms.ModelForm): item = forms.ModelChoiceField(queryset=Item.objects.all(),widget=forms.HiddenInput()) plan = forms.ModelChoiceField(queryset=Plan.objects.all(),widget=forms.HiddenInput()) category = "" < assign dynamically on form creation > item = "" < assign dynamically on form creation > class Meta: model = BudgetValue fields = ('item','plan','value') What I started out with is just creating a dictionary of budgetvalue.item.category.name, budgetvalue.item.name, and the form for each budget value. This gets passed to the template and I render it as I intended. I'm assuming that the ordering of the forms in the formset and the querset used to genererate the formset keep the budgetvalues in the same order and the dictionary is created correctly. That is the budgetvalue.item.name is associated with the correct form. This scares me and I'm thinking there has to be a better way. Any help would be greatly appreciated.

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• Django aggregate query generating SQL error

  - by meepmeep

  I'm using Django 1.1.1 on a SQL Server 2005 db using the latest sqlserver_ado library. models.py includes: class Project(models.Model): name = models.CharField(max_length=50) class Thing(models.Model): project = models.ForeignKey(Project) reference = models.CharField(max_length=50) class ThingMonth(models.Model): thing = models.ForeignKey(Thing) timestamp = models.DateTimeField() ThingMonthValue = models.FloatField() class Meta: db_table = u'ThingMonthSummary' In a view, I have retrieved a queryset called 'things' which contains 25 Things: things = Thing.objects.select_related().filter(project=1).order_by('reference') I then want to do an aggregate query to get the average ThingMonthValue for the first 20 of those Things for a certain period, and the same value for the last 5. For the first 20 I do: averageThingMonthValue = ThingMonth.objects.filter(turbine__in=things[:20],timestamp__range="2009-01-01 00:00","2010-03-00:00")).aggregate(Avg('ThingMonthValue'))['ThingMonthValue__avg'] This works fine, and returns the desired value. For the last 5 I do: averageThingMonthValue = ThingMonth.objects.filter(turbine__in=things[20:],timestamp__range="2009-01-01 00:00","2010-03-00:00")).aggregate(Avg('ThingMonthValue'))['ThingMonthValue__avg'] But for this I get an SQL error: 'Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.' The SQL query being used by django reads: SELECT AVG([ThingMonthSummary].[ThingMonthValue]) AS [ThingMonthValue__avg] FROM [ThingMonthSummary] WHERE ([ThingMonthSummary].[thing_id] IN (SELECT _row_num, [id] FROM ( SELECT ROW_NUMBER() OVER ( ORDER BY [AAAA].[id] ASC) as _row_num, [AAAA].[id] FROM ( SELECT U0.[id] FROM [Thing] U0 WHERE U0.[project_id] = 1 ) AS [AAAA]) as QQQ where 20 < _row_num) AND [ThingMonthSummary].[timestamp] BETWEEN '01/01/09 00:00:00' and '03/01/10 00:00:00') Any idea why it works for one slice of the Things and not the second? I've checked and the two slices do contain the desired Things correctly.

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• django admin how to limit selectbox values

  - by SledgehammerPL

  model: class Store(models.Model): name = models.CharField(max_length = 20) class Admin: pass def __unicode__(self): return self.name class Stock(Store): products = models.ManyToManyField(Product) class Admin: pass def __unicode__(self): return self.name class Product(models.Model): name = models.CharField(max_length = 128, unique = True) parent = models.ForeignKey('self', null = True, blank = True, related_name='children') (...) def __unicode__(self): return self.name mptt.register(Product, order_insertion_by = ['name']) admin.py: from bar.drinkstore.models import Store, Stock from django.contrib import admin admin.site.register(Store) admin.site.register(Stock) Now when I look at admin site I can select any product from the list. But I'd like to have a limited choice - only leaves. In mptt class there's function: is_leaf_node() -- returns True if the model instance is a leaf node (it has no children), False otherwise. But I have no idea how to connect it I'm trying to make a subclass: in admin.py: from bar.drinkstore.models import Store, Stock from django.contrib import admin admin.site.register(Store) class StockAdmin(admin.ModelAdmin): def queryset(self, request): qs = super(StockAdmin, self).queryset(request).filter(ihavenoideawhatfilter) admin.site.register(Stock, StockAdmin) but I'm not sure if it's right way, and what filter set.

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• Django: ordering by backward related field property

  - by Silver Light

  Hello! I have two models related one-to-many: a Post and a Comment: class Post(models.Model): title = models.CharField(max_length=200); content = models.TextField(); class Comment(models.Model): post = models.ForeignKey('Post'); body = models.TextField(); date_added = models.DateTimeField(); I want to get a list of posts, ordered by the date of the latest comment. If I would write a custom SQL query it would look like this: SELECT `posts`.`*`, MAX(`comments`.`date_added`) AS `date_of_lat_comment` FROM `posts`, `comments` WHERE `posts`.`id` = `comments`.`post_id` GROUP BY `posts`.`id` ORDER BY `date_of_lat_comment` DESC How can I do same thing using django ORM?

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• Edit the opposite side of a many to many relationship with django generic form

  - by Ed

  I have two models: class Actor(models.Model): name = models.CharField(max_length=30, unique = True) event = models.ManyToManyField(Event, blank=True, null=True) class Event(models.Model): name = models.CharField(max_length=30, unique = True) long_description = models.TextField(blank=True, null=True) In a previous question: http://stackoverflow.com/questions/2503243/django-form-linking-2-models-by-many-to-many-field, I created an EventForm with a save function: class EventForm(forms.ModelForm): class Meta: model = Event def save(self, commit=True): instance = forms.ModelForm.save(self) instance.actors_set.clear() for actor in self.cleaned_data['actors']: instance.actors_set.add(actors) return instance This allowed me to add m2m links from the other side of the defined m2m connection. Now I want to edit the entry. I've been using a generic function: def generic_edit(request, modelname, object_id): modelname = modelname.lower() form_class = form_dict[modelname] return update_object(request, form_class = form_class, object_id = object_id, template_name = 'createdit.html' ) but this pulls in all the info except the many-to-many selections saved to this object. I think I need to do something similar to this: http://stackoverflow.com/questions/1700202/editing-both-sides-of-m2m-in-admin-page, but I haven't figured it out. How do I use the generic update_object to edit the other side of many-to-many link?

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• Django Grouping Query

  - by Matt

  I have the following (simplified) models: class Donation(models.Model): entry_date = models.DateTimeField() class Category(models.Model): name = models.CharField() class Item(models.Model): donation = models.ForeignKey(Donation) category = models.ForeignKey(Category) I'm trying to display the total number of items, per category, grouped by the donation year. I've tried this: Donation.objects.extra(select={'year': "django_date_trunc('year', %s.entry_date)" % Donation._meta.db_table}).values('year', 'item__category__name').annotate(items=Sum('item__quantity')) But I get a Field Error on item__category__name. I've also tried: Item.objects.extra(select={"year": "django_date_trunc('year', entry_date)"}, tables=["donations_donation"]).values("year", "category__name").annotate(items=Sum("quantity")).order_by() Which generally gets me what I want, but the item quantity count is multiplied by the number of donation records. Any ideas? Basically I want to display this: 2010 - Category 1: 10 items - Category 2: 17 items 2009 - Category 1: 5 items - Category 3: 8 items

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• Dropdown sorting in django-admin

  - by Andrey

  I'd like to know how can I sort values in the Django admin dropdowns. For example, I have a model called Article with a foreign key pointing to the Users model, smth like: class Article(models.Model): title = models.CharField(_('Title'), max_length=200) slug = models.SlugField(_('Slug'), unique_for_date='publish') author = models.ForeignKey(User) body = models.TextField(_('Body')) status = models.IntegerField(_('Status')) categories = models.ManyToManyField(Category, blank=True) publish = models.DateTimeField(_('Publish date')) I edit this model in django admin: class ArticleAdmin(admin.ModelAdmin): list_display = ('title', 'publish', 'status') list_filter = ('publish', 'categories', 'status') search_fields = ('title', 'body') prepopulated_fields = {'slug': ('title',)} admin.site.register(Article, ArticleAdmin) and of course it makes the nice user select dropdown for me, but it's not sorted and it takes a lot of time to find a user by username.

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• django simple approach to multi-field search

  - by Scott Willman

  I have a simple address book app that I want to make searchable. The model would look something like: class Address(models.Model): address1 = models.CharField("Address Line 1", max_length=128) address2 = models.CharField("Address Line 2", max_length=128) city = models.CharField("City", max_length=128) state = models.CharField("State", max_length=24) zipCode = models.CharField("Zip Code", max_length=24) def __unicode__(self): return "%s %s, %s, %s, %s" % (self.address1, self.address2, self.city, self.state, self.zipCode) class Entry(models.Model): name = models.CharField("Official School Name", max_length=128) createdBy = models.ForeignKey(User) address = models.ForeignKey(Address, unique=True) def __unicode__(self): return "%s - %s, %s" % (self.name, self.address.city, self.address.state) I want the searching to be fairly loose, like: Bank of America Los Angeles 91345. It seems like I want a field that contains all of those elements into one that I can search, but that also seems redundant. I was hoping I could add a method to the Entry model like this: def _getSearchText(self): return "%s %s %s" % (self.name, self.address, self.mascot) searchText = property(_getSearchText) ...and search that as a field, but I suppose that's wishful thinking... How should I approach this using basic Django and SqLite (this is a learning exercise). Thank you!!

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• How to provide an inline model field with a queryset choices without losing field value for inline r

  - by Judith Boonstra

  The code displayed below is providing the choices I need for the app field, and the choices I need for the attr field when using Admin. I am having a problem with the attr field on the inline form for already saved records. The attr selected for these saved does show in small print above the field, but not within the field itself. # MODELS: Class Vocab(models.Model): entity = models.Charfield, max_length = 40, unique = True) Class App(models.Model): name = models.ForeignKey(Vocab, related_name = 'vocab_appname', unique = True) app = SelfForeignKey('self, verbose_name = 'parent', blank = True, null = True) attr = models.ManyToManyField(Vocab, related_name = 'vocab_appattr', through ='AppAttr' def parqs(self): a method that provides a queryset consisting of available apps from vocab, excluding self and any apps within the current app's dependent line. def attrqs(self): a method that provides a queryset consisting of available attr from vocab excluding those already selected by current app, 2) those already selected by any apps within the current app's parent line, and 3) those selected by any apps within the current app's dependent line. Class AppAttr(models.Model): app = models.ForeignKey(App) attr = models.ForeignKey(Vocab) # FORMS: from models import AppAttr def appattr_form_callback(instance, field, *args, **kwargs) if field.name = 'attr': if instance: return field.formfield(queryset = instance.attrqs(), *kwargs) return field.formfield(*kwargs) # ADMIN: necessary imports class AppAttrInline(admin.TabularInline): model = AppAttr def get_formset(self, request, obj = None, **kwargs): kwargs['formfield_callback'] = curry(appattr_form_callback, obj) return super(AppAttrInline, self).get_formset(request, obj, **kwargs) class AppForm(forms.ModelForm): class Meta: model = App def __init__(self, *args, **kwargs): super(AppForm, self).__init__(*args, **kwargs) if self.instance.id is None: working = App.objects.all() else: thisrec = App.objects.get(id = self.instance.id) working = thisrec.parqs() self.fields['par'].queryset = working class AppAdmin(admin.ModelAdmin): form = AppForm inlines = [AppAttrInline,] fieldsets = .......... necessary register statements

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• Django display manytomany field in form when definition is on other model

  - by John

  Hi I have the definition for my manytomany relationship on one model but want to display the field on the form of my other model. How do I do this? for example: # classes class modelA(models.Model): name = models.CharField(max_length=300) manytomany = models.ManyToManyField(modelA) class modelB(models.Model): name = models.CharField(max_length=300) # forms class modelBForm(forms.ModelForm): class Meta: model = modelB If I then used modelBForm it would show a select box with the models from modelA rather than just name. Thanks

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• Overwrite queryset which builds filter sidebar

  - by cw

  Hi, I'm writing a hockey database/manager. So I have the following models: class Team(models.Model): name = models.CharField(max_length=60) class Game(models.Model): home_team = models.ForeignKey(Team,related_name='home_team') away_team = models.ForeignKey(Team,related_name='away_team') class SeasonStats(models.Model): team = models.ForeignKey(Team) Ok, so my problem is the following. There are a lot of teams, but Stats are just managed for my Club. So if I use "list_display" in the admin backend, I'd like to modify/overwrite the queryset which builds the sidebar for filtering, to just display our home teams as a filter option. Is this somehow possible in Django? I already made a custom form like this class SeasonPlayerStatsAdminForm(forms.ModelForm): team = forms.ModelChoiceField(Team.objects.filter(club__home=True)) So now just the filtering is missing. Any ideas?

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• Django Aggregation Across Reverse Relationship

  - by Tom

  Given these two models: class Profile(models.Model): user = models.ForeignKey(User, unique=True, verbose_name=_('user')) about = models.TextField(_('about'), blank=True) zip = models.CharField(max_length=10, verbose_name='zip code', blank=True) website = models.URLField(_('website'), blank=True, verify_exists=False) class ProfileView(models.Model): profile = models.ForeignKey(Profile) viewer = models.ForeignKey(User, blank=True, null=True) created = models.DateTimeField(auto_now_add=True) I want to get all profiles sorted by total views. I can get a list of profile ids sorted by total views with: ProfileView.objects.values('profile').annotate(Count('profile')).order_by('-profile__count') But that's just a dictionary of profile ids, which means I then have to loop over it and put together a list of profile objects. Which is a number of additional queries and still doesn't result in a QuerySet. At that point, I might as well drop to raw SQL. Before I do, is there a way to do this from the Profile model? ProfileViews are related via a ForeignKey field, but it's not as though the Profile model knows that, so I'm not sure how to tie the two together. As an aside, I realize I could just store views as a property on the Profile model and that may turn out to be what I do here, but I'm still interested in learning how to better use the Aggregation functions.

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• Django: remove all m2m relations

  - by pistacchio

  Hi, if I have two simple models: class Tag(models.Model): name = models.CharField(max_length=100) class Post(models.Model): title = models.CharField(max_length=100) tags = models.ManyToManyField(Tag, blank=True) given a Post object with a number of Tags added to it, I know hot to remove any of them, but how to do a mass remove (remove all)? Thanks

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• Tallying records using annotate() not working as should.

  - by 47

  I have two classes: Vehicle and Issues....a Vehicle object can have several issues recorded in the Issues class. What I want to do is to have a list of all issues, with each vehicle appearing only once and the total number of issues shown, plus other details....clicking on the record will then take the user to another page with all those issues for a selected vehicle shown in detail now. I tried this out using annotate, but I could only access the count and vehicle foreign key, but none of the other fields in the Vehicle class. class Issues(models.Model): vehicle = models.ForeignKey(Vehicle) description = models.CharField('Issue Description', max_length=30,) type = models.CharField(max_length=10, default='Other') status = models.CharField(max_length=12, default='Pending') priority = models.IntegerField(default='8', editable=False) date_time_added = models.DateTimeField(default=datetime.today, editable=False) last_updated = models.DateTimeField(default=datetime.today, editable=False) def __unicode__(self): return self.description The code I was using to annotate is: issues = Issues.objects.all().values('vehicle').annotate(count=Count('id')) What could be the problem?

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• How to join the results of two tables in django python

  - by user1787524

  I have two models class Weather(model.model): region = models.ForeignKey(Region) district = models.ForeignKey(District) temp_max = models.IntegerField(blank=True, null=True, verbose_name='Max temperature (C)') temp_min = models.IntegerField(blank=True, null=True, verbose_name='Min temperature (C)') and class Plan(model.model): name = tinymce_models.HTMLField(blank=True, null=True) region = models.ForeignKey(Region) district = models.ForeignKey(District) Provided for every region and district have unique row. I want to combine the result so that i can get all the columns of both tables These two Models are not related to each other. ' I need to make the join like join weather w on w.region = A.region and w.distric = A.district so that result contains all the columns in everyobject like obj.temp_max etc

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• Config import on network-manager-openvpn

  - by Toki Tahmid

  I'm trying to use a free service using the OpenVPN protocol using OpenVPN's GUI module in the network manager. The config worked perfectly well as .ovpn on Windows. The behavior in Windows is such that I ran OpenVPN GUI and chose to connect to this particular VPN. It would then show the activity in the attempt to connect and opens a dialog box for username/password authentication. I've successfully imported all the configurations by changing the file type to .conf and using the import feature in network manager. However, attempting to connect would simply display the network manager's attempting to connect animation, but ultimately end with a notification of connection timing out. No prompt asking for authentication would appear at all, nor can I find any feature to prefix the authentication details. client dev tun proto tcp remote miami.proxpn.com 443 resolv-retry infinite nobind persist-key persist-tun ca ca.crt cert client.crt key client.key cipher BF-CBC keysize 512 comp-lzo verb 4 mute 5 tun-mtu 1500 mssfix 1450 auth-user-pass reneg-sec 0 # If you are connecting through an # HTTP proxy to reach the actual OpenVPN # server, put the proxy server/IP and # port number here. See the man page # if your proxy server requires # authentication. ;http-proxy-retry # retry on connection failures ;http-proxy [proxy server] [proxy port #] Needless to say, but I've downloaded all the required packages for setting up OpenVPN connections. By the way, as you can see above, .key and .crt files location are specified to be in the same directory as the config file. After importing the config file, if were to remove them, would it cause any problem? Note, I haven't removed them, so the problem I'm facing is not due to the absence of these files.

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• How to Assure an Effective Data Model

  As a general rule in my opinion the effectiveness of a data model can be directly related to the accuracy and complexity of a project’s requirements. For example there is no need to work on very detailed data models when the details surrounding a specific data model have not been defined or even clarified. Developing data models when the clarity of project requirements is limited tends to introduce designed issues because the proper details to create an effective data model are not even known. One way to avoid this issue is to create data models that correspond to the complexity of the existing project requirements so that when requirements are updated then new data models can be created based any new discoveries regarding requirements on a fine grain level.  This allows for data models to be composed of general entities to be created initially when a project’s requirements are very vague and then the entities are refined as new and more substantial requirements are defined or redefined. This promotes communication amongst all stakeholders within a project as they go through the process of defining and finalizing project requirements.In addition, here are some general tips that can be applied to projects in regards to data modeling.Initially model all data generally and slowly reactor the data model as new requirements and business constraints are applied to a project.Ensure that data modelers have the proper tools and training they need to design a data model accurately.Create a common location for all project documents so that everyone will be able to review a project’s data models along with any other project documentation.All data models should follow a clear naming schema that tells readers the intended purpose for the data and how it is going to be applied within a project.

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• Package Manager cannot access repositories but internet is working

  - by kazman

  I am currently at a conference in another country and my package manager cannot access repositories. My internet is working fine and I can ping the repositories or go to them in a browser, but package manager fails to access them. If I sudo apt-get update it throws Something wicked happened resolving 'wwwproxy:3128' (-5 - No address associated with hostname) (or Ign's). This proxy corresponds to my proxy at my office back at home, but I have disabled proxy in the package manager. Scanning for best repository doesn't work either, it doesn't manage to connect to any. I have searched for this online and have checked things about my apt.conf file. My apt.conf contains: Acquire::http::proxy "http://wwwproxy:3128/"; Acquire::https::proxy "https://wwwproxy:3128/"; Acquire::ftp::proxy "ftp://wwwproxy:3128/"; Acquire::socks::proxy "socks://wwwproxy:3128/"; If I remove apt.conf (or replace with blank), it makes no difference. I don't see that it should since I am connecting directly (and have set it so in my network options in Package manager network settings) I have also tried some things with resolv.conf (changing name address to primary and secondary dns) to no avail. (im not sure if this would help, following other advice) I am running 12.04. (I wrote this very quickly and wrote down everything I have tried to possibly shorten the troubleshooting process, have very limited time between lectures and need this sorted asap, my apologies)

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• Unable to cast transparent proxy to type &lt;type&gt;

  - by Rick Strahl

  This is not the first time I've run into this wonderful error while creating new AppDomains in .NET and then trying to load types and access them across App Domains. In almost all cases the problem I've run into with this error the problem comes from the two AppDomains involved loading different copies of the same type. Unless the types match exactly and come exactly from the same assembly the typecast will fail. The most common scenario is that the types are loaded from different assemblies - as unlikely as that sounds. An Example of Failure To give some context, I'm working on some old code in Html Help Builder that creates a new AppDomain in order to parse assembly information for documentation purposes. I create a new AppDomain in order to load up an assembly process it and then immediately unload it along with the AppDomain. The AppDomain allows for unloading that otherwise wouldn't be possible as well as isolating my code from the assembly that's being loaded. The process to accomplish this is fairly established and I use it for lots of applications that use add-in like functionality - basically anywhere where code needs to be isolated and have the ability to be unloaded. My pattern for this is: Create a new AppDomain Load a Factory Class into the AppDomain Use the Factory Class to load additional types from the remote domain Here's the relevant code from my TypeParserFactory that creates a domain and then loads a specific type - TypeParser - that is accessed cross-AppDomain in the parent domain:public class TypeParserFactory : System.MarshalByRefObject,IDisposable { …/// <summary> /// TypeParser Factory method that loads the TypeParser /// object into a new AppDomain so it can be unloaded. /// Creates AppDomain and creates type. /// </summary> /// <returns></returns> public TypeParser CreateTypeParser() { if (!CreateAppDomain(null)) return null; /// Create the instance inside of the new AppDomain /// Note: remote domain uses local EXE's AppBasePath!!! TypeParser parser = null; try { Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); } catch (Exception ex) { this.ErrorMessage = ex.GetBaseException().Message; return null; } return parser; } private bool CreateAppDomain(string lcAppDomain) { if (lcAppDomain == null) lcAppDomain = "wwReflection" + Guid.NewGuid().ToString().GetHashCode().ToString("x"); AppDomainSetup setup = new AppDomainSetup(); // *** Point at current directory setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory; //setup.PrivateBinPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"); this.LocalAppDomain = AppDomain.CreateDomain(lcAppDomain,null,setup); // Need a custom resolver so we can load assembly from non current path AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve); return true; } …} Note that the classes must be either [Serializable] (by value) or inherit from MarshalByRefObject in order to be accessible remotely. Here I need to call methods on the remote object so all classes are MarshalByRefObject. The specific problem code is the loading up a new type which points at an assembly that visible both in the current domain and the remote domain and then instantiates a type from it. This is the code in question:Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); The last line of code is what blows up with the Unable to cast transparent proxy to type <type> error. Without the cast the code actually returns a TransparentProxy instance, but the cast is what blows up. In other words I AM in fact getting a TypeParser instance back but it can't be cast to the TypeParser type that is loaded in the current AppDomain. Finding the Problem To see what's going on I tried using the .NET 4.0 dynamic type on the result and lo and behold it worked with dynamic - the value returned is actually a TypeParser instance: Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; object objparser = this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); // dynamic works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // casting fails parser = (TypeParser)objparser; So clearly a TypeParser type is coming back, but nevertheless it's not the right one. Hmmm… mysterious.Another couple of tries reveal the problem however:// works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // c:\wwapps\wwhelp\wwReflection20.dll (Current Execution Folder) string info3 = typeof(TypeParser).Assembly.CodeBase; // c:\program files\vfp9\wwReflection20.dll (my COM client EXE's folder) string info4 = dynParser.GetType().Assembly.CodeBase; // fails parser = (TypeParser)objparser; As you can see the second value is coming from a totally different assembly. Note that this is even though I EXPLICITLY SPECIFIED an assembly path to load the assembly from! Instead .NET decided to load the assembly from the original ApplicationBase folder. Ouch! How I actually tracked this down was a little more tedious: I added a method like this to both the factory and the instance types and then compared notes:public string GetVersionInfo() { return ".NET Version: " + Environment.Version.ToString() + "\r\n" + "wwReflection Assembly: " + typeof(TypeParserFactory).Assembly.CodeBase.Replace("file:///", "").Replace("/", "\\") + "\r\n" + "Assembly Cur Dir: " + Directory.GetCurrentDirectory() + "\r\n" + "ApplicationBase: " + AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "\r\n" + "App Domain: " + AppDomain.CurrentDomain.FriendlyName + "\r\n"; } For the factory I got: .NET Version: 4.0.30319.239wwReflection Assembly: c:\wwapps\wwhelp\bin\wwreflection20.dllAssembly Cur Dir: c:\wwapps\wwhelpApplicationBase: C:\Programs\vfp9\App Domain: wwReflection534cfa1f For the instance type I got: .NET Version: 4.0.30319.239wwReflection Assembly: C:\\Programs\\vfp9\wwreflection20.dllAssembly Cur Dir: c:\\wwapps\\wwhelpApplicationBase: C:\\Programs\\vfp9\App Domain: wwDotNetBridge_56006605 which clearly shows the problem. You can see that both are loading from different appDomains but the each is loading the assembly from a different location. Probably a better solution yet (for ANY kind of assembly loading problem) is to use the .NET Fusion Log Viewer to trace assembly loads.The Fusion viewer will show a load trace for each assembly loaded and where it's looking to find it. Here's what the viewer looks like: The last trace above that I found for the second wwReflection20 load (the one that is wonky) looks like this:*** Assembly Binder Log Entry (1/13/2012 @ 3:06:49 AM) *** The operation was successful. Bind result: hr = 0x0. The operation completed successfully. Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\V4.0.30319\clr.dll Running under executable c:\programs\vfp9\vfp9.exe --- A detailed error log follows. === Pre-bind state information === LOG: User = Ras\ricks LOG: DisplayName = wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null (Fully-specified) LOG: Appbase = file:///C:/Programs/vfp9/ LOG: Initial PrivatePath = NULL LOG: Dynamic Base = NULL LOG: Cache Base = NULL LOG: AppName = vfp9.exe Calling assembly : (Unknown). === LOG: This bind starts in default load context. LOG: Using application configuration file: C:\Programs\vfp9\vfp9.exe.Config LOG: Using host configuration file: LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\V4.0.30319\config\machine.config. LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind). LOG: Attempting download of new URL file:///C:/Programs/vfp9/wwReflection20.DLL. LOG: Assembly download was successful. Attempting setup of file: C:\Programs\vfp9\wwReflection20.dll LOG: Entering run-from-source setup phase. LOG: Assembly Name is: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null LOG: Binding succeeds. Returns assembly from C:\Programs\vfp9\wwReflection20.dll. LOG: Assembly is loaded in default load context. WRN: The same assembly was loaded into multiple contexts of an application domain: WRN: Context: Default | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: Context: LoadFrom | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: This might lead to runtime failures. WRN: It is recommended to inspect your application on whether this is intentional or not. WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue. Notice that the fusion log clearly shows that the .NET loader makes no attempt to even load the assembly from the path I explicitly specified. Remember your Assembly Locations As mentioned earlier all failures I've seen like this ultimately resulted from different versions of the same type being available in the two AppDomains. At first sight that seems ridiculous - how could the types be different and why would you have multiple assemblies - but there are actually a number of scenarios where it's quite possible to have multiple copies of the same assembly floating around in multiple places. If you're hosting different environments (like hosting the Razor Engine, or ASP.NET Runtime for example) it's common to create a private BIN folder and it's important to make sure that there's no overlap of assemblies. In my case of Html Help Builder the problem started because I'm using COM interop to access the .NET assembly and the above code. COM Interop has very specific requirements on where assemblies can be found and because I was mucking around with the loader code today, I ended up moving assemblies around to a new location for explicit loading. The explicit load works in the main AppDomain, but failed in the remote domain as I showed. The solution here was simple enough: Delete the extraneous assembly which was left around by accident. Not a common problem, but one that when it bites is pretty nasty to figure out because it seems so unlikely that types wouldn't match. I know I've run into this a few times and writing this down hopefully will make me remember in the future rather than poking around again for an hour trying to debug the issue as I did today. Hopefully it'll save some of you some time as well in the future.© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  COM   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Using Castle DynamicProxy is it possible to change the invocation target on class proxy?

  - by Gareth D

  Hi Using Castle DynamicProxy v2, I'd like to change the target of an invocation for a class proxy. The new target is simply a different instance of the same type as the original target. The target types do not implement a common interface so I cannot use the IProxyTargetAccessor as detailed in Krzysztof's post on the subject - I cannot cast from a class proxy invocator to a IProxyTargetAccessor. Is there a way to do this?

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• How do I set up a proxy object in the main application NIB?

  - by zoul

  Hello! I would like to set up a proxy object in the application NIB file. The problem is that the NIB file is the main application NIB that gets loaded automatically by the application and therefore I cannot set up the UINibProxiedObjectsKey dictionary as described in the documentation. Is there a way to set up a proxy object in the main application NIB? Or can I tap into the code that loads the main application NIB?

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• [Castle Dynamic Proxy] What really interceptors do with my c# class?

  - by Pandiya Chendur

  I was asked to implement castle dynamic proxy in my asp.net web application and i was going through couple of articles which i got from Castle Project and Code Project about castle dynamic proxy in asp.net web application.... Both articles delt with creating interceptors but i can't get the idea why interceptors are used with classes.... Why should i intercept my class which is behaving properly?

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