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  • Row Source - combo box, filtering what pops up in a combo box by date

    - by primus285
    so I have a combo box that I want to pop up when somebody wants to search by year. It will allow them to see in that combo box only results that happened in a certain year. so far I have something like SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE (((Database_New.Date) >= DateValue('01/01/2001') AND (((Database_New.Date) <= DateValue('12/031/2001'))); or SELECT DISTINCT Database_New.ASEC FROM Database_New WHERE (((Database_New.Date) >= BETWEEN DateValue('01/01/2001') AND DateValue('12/31/2001’))); as you can see, the kicker is that I am already sorting the thing with SELECT DISTINCT under the ASEC field. But I want to filter it one more by year so a whole bunch of ASEC values that didnt happen in that year (and there are quite a few that happen rarely, or would onyl be associeted with one year) do not pop up as avalible. so far I get an error like "Syntax error in query expression '(((Database_New.Date) = DateValue('01/01/2001') AND (((Database_New.Date) <= DateValue('12/031/2001')))' and I am a VBA person, not quite as good at debuggin SQL. Is it something easy? or will it simply not work the way I have it set up.

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  • sqlalchemy relation through another (declarative)

    - by clayg
    Is anyone familiar with ActiveRecord's "has_many :through" relations for models? I'm not really a Rails guy, but that's basically what I'm trying to do. As a contrived example consider Projects, Programmers, and Assignments: from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker from sqlalchemy import Column, ForeignKey from sqlalchemy.types import Integer, String, Text from sqlalchemy.orm import relation from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Assignment(Base): __tablename__ = 'assignment' id = Column(Integer, primary_key=True) description = Column(Text) programmer_id = Column(Integer, ForeignKey('programmer.id')) project_id = Column(Integer, ForeignKey('project.id')) def __init__(self, description=description): self.description = description def __repr__(self): return '<Assignment("%s")>' % self.description class Programmer(Base): __tablename__ = 'programmer' id = Column(Integer, primary_key=True) name = Column(String(64)) assignments = relation("Assignment", backref='programmer') def __init__(self, name=name): self.name = name def __repr__(self): return '<Programmer("%s")>' % self.name class Project(Base): __tablename__ = 'project' id = Column(Integer, primary_key=True) name = Column(String(64)) description = Column(Text) assignments = relation("Assignment", backref='project') def __init__(self, name=name, description=description): self.name = name self.description = description def __repr__(self): return '<Project("%s", "%s...")>' % (self.name, self.description[:10]) engine = create_engine('sqlite://') Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session() Projects have many Assignments. Programmers have many Assignments. (understatement?) But in my office at least, Programmers also have many Projects - I'd like this relationship to be inferred through the Assignments assigned to the Programmer. I'd like the Programmer model to have a attribute "projects" which will return a list of Projects associated to the Programmer through the Assignment model. me = session.query(Programmer).filter_by(name='clay').one() projects = session.query(Project).\ join(Project.assignments).\ join(Assignment.programmer).\ filter(Programmer.id==me.id).all() How can I describe this relationship clearly and simply using the sqlalchemy declarative syntax? Thanks!

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  • Why put a DAO layer over a persistence layer (like JDO or Hibernate)

    - by Todd Owen
    Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top of mature ORM frameworks like JDO and Hibernate, and I wonder if that is really a good idea. I am developing a web service using JDO as the persistence layer, and am considering whether or not to introduce DAOs. I foresee a problem when dealing with a particular class which contains a map of other objects: public class Book { // Book description in various languages, indexed by ISO language codes private Map<String,BookDescription> descriptions; } JDO is clever enough to map this to a foreign key constraint between the "BOOKS" and "BOOKDESCRIPTIONS" tables. It transparently loads the BookDescription objects (using lazy loading, I believe), and persists them when the Book object is persisted. If I was to introduce a "data access layer" and write a class like BookDao, and encapsulate all the JDO code within this, then wouldn't this JDO's transparent loading of the child objects be circumventing the data access layer? For consistency, shouldn't all the BookDescription objects be loaded and persisted via some BookDescriptionDao object (or BookDao.loadDescription method)? Yet refactoring in that way would make manipulating the model needlessly complicated. So my question is, what's wrong with calling JDO (or Hibernate, or whatever ORM you fancy) directly in the business layer? Its syntax is already quite concise, and it is datastore-agnostic. What is the advantage, if any, of encapsulating it in Data Access Objects?

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  • Looking for good PHP editor or IDE with 'IntelliSense'

    - by Andrew
    Hello, I'm looking for suitable PHP Editor or IDE with syntax auto-completion. I've tried trial versions of programs like Zend Studio, PHPDesigner, NetBeans PHP, NuSphere PhpED, and similar -- but none of them fully satisfied me. I quite liked hint window with detailed info about what function does and what it returns. Also I liked the way NetBeans auto-complete code (for example inserts all required parameters in function declaration as "dummy fields" and then you can jump between them using TAB in order to edit them). On the other hand, environment of NetBeans doesn't belong to the nicest. In this regard I prefer PHPDesigner with its sleek and light interface. At this moment I don't use any of the debugging options, since I don't know yet how to use profiller, breakpoints, watches and what not, so at this point my only concern is good autocompletion. For this purpose NetBean would be great choice, but with future in mind I am not sure debugging will be good in NetBeans, especially as I would prefer to use remote Linux server for this. So in short, I'm looking for editor that: Have similar code auto-completion (IntelliSense) like NetBeans Allow you to debug code using remote server (or sets up own debugging server like PHPDesigner does) without need to run Apache and similar on local computer Is preferably easy to use / intuitive interface Any ideas?

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  • how do I make a portable isnan/isinf function.

    - by monkeyking
    I've been using isinf,isnan functions on linux platforms which worked perfectly. But this didn't work on osx, so I decided to use std::isinf std::isnan which works on both linux and osx. But the intel compiler doesn't recognize it, and I guess its a bug in the intel compiler according to http://software.intel.com/en-us/forums/showthread.php?t=64188 So now I just want to avoid the hassle and define my own isinf,isnan implementation. Does anyone know how this could be done Thanks edit: I ended up doing this in my sourcecode for making isinf/isnan working #include <iostream> #include <cmath> #ifdef __INTEL_COMPILER #include <mathimf.h> #endif int isnan_local(double x) { #ifdef __INTEL_COMPILER return isnan(x); #else return std::isnan(x); #endif } int isinf_local(double x) { #ifdef __INTEL_COMPILER return isinf(x); #else return std::isinf(x); #endif } int myChk(double a){ std::cerr<<"val is: "<<a <<"\t"; if(isnan_local(a)) std::cerr<<"program says isnan"; if(isinf_local(a)) std::cerr<<"program says isinf"; std::cerr<<"\n"; return 0; } int main(){ double a = 0; myChk(a); myChk(log(a)); myChk(-log(a)); myChk(0/log(a)); myChk(log(a)/log(a)); return 0; }

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  • Adding a ServiceReference programmatically during async postback

    - by Oliver
    Is it possible to add a new ServiceReference instance to the ScriptManager on the Page during an asynchronous postback so that subsequently I can use the referenced web service through client side script? I'm trying to do this inside a UserControl that sits inside a Repeater, that's why adding the ScriptReference programmatically during Page_Load does not work here. EDIT 2: This is the code I call from my UserControl which does not do what I expect (adding the ServiceReference to the ScriptManager during the async postback): private void RegisterWebservice(Type webserviceType) { var scm = ScriptManager.GetCurrent(Page); if (scm == null) throw new InvalidOperationException("ScriptManager needed on the Page!"); scm.Services.Add(new ServiceReference("~/" + webserviceType.Name + ".asmx")); } My goal is for my my UserControl to be as unobtrusive to the surrounding application as possible; otherwise I would have to statically define the ServiceReference in a ScriptManagerProxy on the containing Page, which is not what I want. EDIT: I must have been tired when I wrote this post... because I meant to write ServiceReference not ScriptReference. Updated the text above accordingly. Now I have: <asp:ScriptManagerProxy runat="server" ID="scmProxy"> <Services> <asp:ServiceReference Path="~/UsefulnessWebService.asmx" /> </Services> </asp:ScriptManagerProxy> but I want to register the webservice in the CodeBehind.

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  • How can I change some specific carps into croaks in Perl?

    - by sid_com
    I tried to catch a carp-warning: carp "$start is > $end" if (warnings::enabled()); ) with eval {} but it didn't work, so I looked in the eval documentation and I discovered, that eval catches only syntax-errors, run-time-errors or executed die-statements. How could I catch a carp warning? #!/usr/bin/env perl use warnings; use strict; use 5.012; use List::Util qw(max min); use Number::Range; my @array; my $max = 20; print "Input (max $max): "; my $in = <>; $in =~ s/\s+//g; $in =~ s/(?<=\d)-/../g; eval { my $range = new Number::Range( $in ); @array = sort { $a <=> $b } $range->range; }; if ( $@ =~ /\d+ is > \d+/ ) { die $@ }; # catch the carp-warning doesn't work die "Input greater than $max not allowed $!" if defined $max and max( @array ) > $max; die "Input '0' or less not allowed $!" if min( @array ) < 1; say "@array";

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  • Embedded Jetty resourceBase classpath URL

    - by drewzilla
    I'm embedding Jetty in a Spring based application. I configure my Jetty server in a Spring context file. The specific part of the configuration I'm having trouble with is this: <bean class="org.eclipse.jetty.webapp.WebAppContext"> <property name="contextPath" value="/" /> <property name="resourceBase" value="????????" /> <property name="parentLoaderPriority" value="true" /> </bean> If you see above, where I've put the ????????, I ideally want the resourceBase to reference a folder on my classpath. I'm deploying my application in a single executable JAR file and have a folder config/web/WEB-INF on my classpath. Jetty seems to be able to handle URLs defined in the resourceBase (e.g. jar:file:/myapp.jar!/config/web) but it doesn't seem to support classpath URLs. I get an IllegalArgumentException if I define something like classpath:config/web. This is a real pain for me. Does anyone know of anyway to achieve this functionality? Thanks, Andrew

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  • XML problem in the basic menu example

    - by arakn0
    Hi there, I am trying to create an app with some menus, an I am following the basic example available in the official android site: http://developer.android.com/guide/topics/ui/menus.html My problems appear when I define the menu in the XML. After creating the folder res/menu and creating the menu_option.xml file from eclipse.... The project (in general) gives an error that can be read from the Problems tab: Unparsed aapt error(s)! Check the console for output Android Packaging Problem So, changing to the Console tab to get more information about the problem, this can be read: [2010-06-02 11:35:54 - TestAudio] Error in an XML file: aborting build. [2010-06-02 11:35:54 - TestAudio] W/ResourceType(11566): Bad XML block: header size 63327 or total size -144759824 is larger than data size 0 [2010-06-02 11:35:54 - TestAudio] /home/User/workspace/TestAudio/res/menu/options_menu.xml:1: error: Error parsing XML: no element found The strange thing is that eclipse recognizes the menu items that I've defined in the XML,I can reference them in the code with no problems and my main activity builds. (and the rest of the files too). Could it be that when eclipse creates a file, for some reason, the Android SDK has problems to read it, or something similar?? The XML code is exactly the same as the one in the example, so I don't really know what is happening. The code in options_menu.xml is this: <menu xmlns:android="http://schemas.android.com/apk/res/android" <item android:id="@+id/new_game" android:title="New Game" / <item android:id="@+id/quit" android:title="Quit" / </menu Thanks in advance for your help!

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  • Python many-to-one mapping (creating equivalence classes)

    - by Adam Matan
    Hi, I have a project of converting one database to another. One of the original database columns defines the row's category. This coulmn should be mapepd to a new category in the new databse. For example, let's assume the original categories are:parrot, spam, cheese_shop, Cleese, Gilliam, Palin Now that's a little verbose for me, And I want to have these rows categorized as sketch, actor - That is, define all the sketches and all the actors as two equivalence classes. >>> monty={'parrot':'sketch', 'spam':'sketch', 'cheese_shop':'sketch', 'Cleese':'actor', 'Gilliam':'actor', 'Palin':'actor'} >>> monty {'Gilliam': 'actor', 'Cleese': 'actor', 'parrot': 'sketch', 'spam': 'sketch', 'Palin': 'actor', 'cheese_shop': 'sketch'} That's quite awkward- I would prefer having something like: monty={ ('parrot','spam','cheese_shop'): 'sketch', ('Cleese', 'Gilliam', 'Palin') : 'actors'} But this, of course, sets the entire tuple as a key: >>> monty['parrot'] Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> monty['parrot'] KeyError: 'parrot' Any ideas how to create an elegant many-to-one dictionary in Python? Thanks, Adam

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  • Creating circular generic references

    - by M. Jessup
    I am writing an application to do some distributed calculations in a peer to peer network. In defining the network I have two class the P2PNetwork and P2PClient. I want these to be generic and so have the definitions of: P2PNetwork<T extends P2PClient<? extends P2PNetwork<T>>> P2PClient<T extends P2PNetwork<? extends T>> with P2PClient defining a method of setNetwork(T network). What I am hoping to describe with this code is: A P2PNetwork is constituted of clients of a certain type A P2PClient may only belong to a network whose clients consist of the same type as this client (the circular-reference) This seems correct to me but if I try to create a non-generic version such as MyP2PClient<MyP2PNetwork<? extends MyP2PClient>> myClient; and other variants I receive numerous errors from the compiler. So my questions are as follows: Is a generic circular reference even possible (I have never seen anything explicitly forbidding it)? Is the above generic definition a correct definition of such a circular relationship? If it is valid, is it the "correct" way to describe such a relationship (i.e. is there another valid definition, which is stylistically preferred)? How would I properly define a non-generic instance of a Client and Server given the proper generic definition?

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  • Subclassing NSArrayController in order to limit size of arrangedObjects

    - by Simone Manganelli
    I'm trying to limit the number of objects in an array controller, but I still want to be able to access the full array, if necessary. A simple solution I came up with was to subclass NSArrayController, and define a new method named "limitedArrangedObjects", that returns a limited number of objects from the real set of arranged objects. (I've seen http://stackoverflow.com/questions/694493/limiting-the-number-of-objects-in-nsarraycontroller , but that doesn't address my problem.) I want this property to be observable via bindings, so I set a dependency to arrangedObjects on it. Problem is, when arrangedObjects is updated, limitedArrangedObjects seems not to be observing the value change in arrangedObjects. I've hooked up an NSCollectionView to limitedArrangedObjects, and zero objects are being displayed. (If I bind it to arrangedObjects instead, all the objects show up as expected.) What's the problem? Here's the relevant code: @property (readonly) NSArray *limitedArrangedObjects; - (NSArray *)limitedArrangedObjects; { NSArray *arrangedObjects = [super arrangedObjects]; NSUInteger upperLimit = 10000; NSUInteger count = [arrangedObjects count]; if (count > upperLimit) count = upperLimit; arrayToReturn = [arrangedObjects subarrayWithRange:NSMakeRange(0, count)]; return arrayToReturn; } + (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key; { NSSet *keyPaths = [super keyPathsForValuesAffectingValueForKey:key]; if ([key isEqualToString:@"limitedArrangedObjects"]) { NSSet *affectingKeys = [NSSet setWithObjects:@"arrangedObjects",nil]; keyPaths = [keyPaths setByAddingObjectsFromSet:affectingKeys]; } return keyPaths; }

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  • XML: what processing rules apply for values intertwined with tags?

    - by iCE-9
    I've started working on a simple XML pull-parser, and as I've just defuzzed my mind on what's correct syntax in XML with regards to certain characters/sequences, ignorable whitespace and such (thank you, http://www.w3schools.com/xml/xml_elements.asp), I realized that I still don't know squat about what can be sketched up as the following case (which Validome finds well-formed very much; note that I only want to use xml files for data storage, no entities, DTD or Schemas needed): <bookstore> <book id="1"> <author>Kurt Vonnegut Jr.</author> <title>Slapstick</title> </book> We drop a pie here. <book id="2">Who cares anyway? <author>Stephen King</author> <title>The Green Mile</title> </book> And another one here. <book id="3"> <author>Next one</author> <title>This time with its own title</title> </book> </bookstore> "We drop a pie here." and "And another one here." are values of the 'bookstore' element. "Who cares anyway?" is a value related to the second 'book' element. How are these processed, if at all? Will "We drop a pie here." and "Another one here." be concatenated to form one value for the 'bookstore' element, or are they treated separately, stored somewhere, affecting the outcome of the parsing of the element they belong to, or...?

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  • Java (or possibly other languages) learning path

    - by bgo
    I am familiar (as a self-learner) with C, python and php such that i can solve some problems involving simple steps (for example, i easily do calculations for physics lab reports with python which normally would take 4x-5x times longer with a calculator). The point here is, as doing such things, i learnt the idea / concepts of programming language and problem solving along with oop or fuctional programming etc. Recently i have started Java and, with the familiarity of other languages, i am doing well for starters but i need guidence. -I am thinking of learning syntax from sun java tutorials and then practicing with codingbat.com or similar sites. I need a reference book that i can study deeper aspects of the topics i am learning. What do you suggest about these? -The problem is (and always have been) the lack of practice. I need coding and problem-solving practices sources. I stuck at the point where i can't figure out what to do next. Can you suggest any source (possibly like codingbat)? If i could plan a learning trail, i can progress faster and efficiently. So i need ideas, comments, suggestions. Thanks in advance.

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  • Compiled Haskell libraries with FFI imports are invalid when imported into GHCI

    - by John Millikin
    I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. I'm using sys_siglist because it's present in a standard library on my system, but I don't believe the actual storage used matters (I discovered this while writing a binding to libidn). If it helps, sys_siglist is defined in <signal.h> as: extern __const char *__const sys_siglist[_NSIG]; I thought this type might be the problem, so I also tried wrapping it in a plain C procedure: #include<stdio.h> const char **test_ffi_import() { printf("C think sys_siglist = %X\n", sys_siglist); return sys_siglist; } However, importing that doesn't change the result, and the printf() call prints the same pointer value as show siglist_a. My suspicion is that it's something to do with static and dynamic library loading. Update: somebody in #haskell suggested this might be 64-bit specific; if anybody tries to reproduce it, can you mention your architecture and whether it worked in a comment? Code as follows: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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  • How to compile Open Flash Chart v.1?

    - by geehertush01
    Let me just say, that I'm a total beginner in anything related to flash. I would like to compile latest version of OFC1 (v.1.9.7). It can be downloaded here: link. Unfortunately no tutorial of how to do it can be found anywhere. I succeeded in compiling OFC2 (v.Lug-Wyrm-Charmer). I installed FlashDevelop, then I found .proj file in the OFC2 package, opened it in FlashDevelop and built the project. It worked fine (although I had to fix some code errors, but it was simple). Unfortunately there is no project file in OFC1 package. I tried to create a new project (Project-New Project-AS3 Project). It created .proj file and few folders (src,bin...). I deleted 'Main.as' from 'src' folder. Then I copied all files from 'actionscript' folder from OFC1 to 'src' project folder. I opened the project and set 'open-flash-char.as' as Document Class (right click on the file in the project tree and 'Set Document Class'). Then I tried to build the project, but got an syntax error with (in 'open-flash-char.as'): #include "prototype.drawCircle.as" #include "prototype.fillCircle.as" #include "String.prototype.replace.as" So I removed "#" signs. But then I got an error ...\ofc1\projtest4\src\open-flash-chart.as: Error: A file found in a source-path must have an externally visible definition. If a definition in the file is meant to be externally visible, please put the definition in a package. I have no idea of how to continue. Maybe I'm doing everything wrong, because OFC1 is written in AS2 (probably), not AS3. I don't know. So my question is: How to compile OFC v.1.9.7?

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  • Partial template specialization: matching on properties of specialized template parameter

    - by Kenzo
    template <typename X, typename Y> class A {}; enum Property {P1,P2}; template <Property P> class B {}; class C {}; Is there any way to define a partial specialization of A such that A<C, B<P1> > would be A's normal template, but A<C, B<P2> > would be the specialization? Replacing the Y template parameter by a template template parameter would be nice, but is there a way to partially specialize it based on P then? template <typename X, template <Property P> typename Y> class A {}; // template <typename X> class A<X,template<> Y<P2> > {}; <-- not valid Is there a way by adding traits to a specialization template<> B<P2> and then using SFINAE in A?

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  • FindControl in DataList Edit Mode

    - by Doug
    As a new .net/C# web begginner, I always get tripped up when I try to use FindControl. Blam -flat on my face. Here is my current FindControl problem: I have an .aspx page and Form, then ajax updatePanel, inside it there is my DataList (DataList1) that has an EditItemTemplate: that has the following: <EditItemTemplate> <asp:Label ID="thumbnailUploadLabel" runat="server" text="Upload a new thumbnail image:"/><br /> <asp:FileUpload ID="thumbnailImageUpload" runat="server" /> <asp:Button ID="thunbnailImageUploadButton" runat="server" Text="Upload Now" OnClick="thumbnailUpload"/><br /> </EditItemTemplate> In my C# code behind I have the OnClick code for the fileUpload object: protected void thumbnailUpload(object s, EventArgs e) { if (thumbnailImageUpload.HasFile) { //get name of the file & upload string imageName = thumbnailImageUpload.FileName; thumbnailImageUpload.SaveAs(MapPath("../../images/merch_sm/" + imageName)); //let'em know that it worked (or didn't) thumbnailUploadLabel.Text = "Image " + imageName + "has been uploaded."; } else { thumbnailUploadLabel.Text = "Please choose a thumbnail image to upload."; } So of course I'm getting "Object reference not set to an instance of an object" for the FileUpload and the Label. What is the correct syntax to find these controls, before dealing with them in the OnClick event? The only way Ive used FindControl is something like: label thumbnailUploadLabel = DataList1.FindControl("thumbnailUploadLabel") as Label; But of course this is throwing the "Object reference not set to an instance of an object" error. Any help is very much appreciated. (I've also seen the 'recursive' code out there that is supposed to make using FindControl easier. Ha! I'm so green at C# that I don't even know how to incorporate those into my project.) Thanks to all for taking a look at this.

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  • Help understanding .NET delegates, events, and eventhandlers

    - by Seth Spearman
    Hello, In the last couple of days I asked a couple of questions about delegates HERE and HERE. I confess...I don't really understand delegates. And I REALLY REALLY REALLY want to understand and master them. (I can define them--type safe function pointers--but since I have little experience with C type languages it is not really helpful.) Can anyone recommend some online resource(s) that will explain delegates in a way that presumes nothing? This is one of those moments where I suspect that VB actually handicaps me because it does some wiring for me behind the scenes. The ideal resource would just explain what delegates are, without reference to anything else like (events and eventhandlers), would show me how all everything is wired up, explain (as I just learned) that delegates are types and what makes them unique as a type (perhaps using a little ildasm magic)). That foundation would then expand to explain how delegates are related to events and eventhandlers which would need a pretty good explanation in there own right. Finally this resource could tie it all together using real examples and explain what wiring DOES happen automatically by the compiler, how to use them, etc. And, oh yeah, when you should and should not use delegates, in other words, downsides and alternatives to using delegates. What say ye? Can any of you point me to resource(s) that can help me begin my journey to mastery? EDIT One last thing. The ideal resource will explain how you can and cannot use delegates in an interface declaration. That is something that really tripped me up. Thanks for your help. Seth

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  • Dealing with Try/Catch Exceptions in Java bytecode? ("stack height inconsistent")

    - by Cogwirrel
    I am trying to do some error handling in java bytecode. I first tried to implement some catch-like subroutines, where I would check for the error condition, and jump to the appropriate subroutine, a little like: iconst_1 iconst_0 dup ifeq calldiverr goto enddivtest calldiverr: jsr divError enddivtest: idiv ...More instructions... divError: getstatic java/lang/System/out Ljava/io/PrintStream; ldc "Oh dear you divided by 0!" invokevirtual java/io/PrintStream/print(Ljava/lang/String;)V The problem with the above is that when I have multiple instructions that jump to this subroutine, I get an error message when running the bytecode, saying that the stack height is inconsistent. Perhaps using exceptions is the best way to get around this? From some googling I have found that you can create instances of Exception classes and initialise them with something like: new java/lang/Exception dup ldc "exception message!" invokespecial java/lang/Exception/<init>(Ljava/lang/String;)V I have also found that you can throw them with athrow and this seems ok. What is confusing me however is exactly how exceptions are caught. There seems to be a magical "Exception table" which glues the throwing and catching of exceptions together, but I do not know how to define one of these when writing bytecode from scratch (and assembling using Jasmin). Can somebody tell me the secret of creating an exception table? And possibly give me an example of exception handling that will assemble with jasmin?

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  • Understanding F# Asynchronous Programming

    - by Yin Zhu
    I kind of know the syntax of asynchronous programming in F#. E.g. let downloadUrl(url:string) = async { let req = HttpWebRequest.Create(url) // Run operation asynchronously let! resp = req.AsyncGetResponse() let stream = resp.GetResponseStream() // Dispose 'StreamReader' when completed use reader = new StreamReader(stream) // Run asynchronously and then return the result return! reader.AsyncReadToEnd() } In F# expert book (and many other sources), they say like let! var = expr simply means "perform the asynchronous operation expr and bind the result to var when the operation completes. Then continue by executing the rest of the computation body" I also know that a new thread is created when performing async operation. My original understanding was that there are two parallel threads after the async operation, one doing I/O and one continuing to execute the async body at the same time. But in this example, I am confused at let! resp = req.AsyncGetResponse() let stream = resp.GetResponseStream() What happens if resp has not started yet and the thread in the async body wants to GetResponseStream? Is this a possible error? So maybe my original understanding was wrong. The quoted sentences in the F# expert book actually means that "creating a new thread, hang the current thread up, when the new thread finishes, wake up the body thread and continue", but in this case I don't see we could save any time. In the original understanding, the time is saved when there are several independent IO operations in one async block so that they could be done at the same time without intervention with each other. But here, if I don't get the response, I cannot create the stream; only I have stream, I can start reading the stream. Where's the time gained?

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  • Enter ID instead of name on submit (form)

    - by Derek
    In my activities table, I have a user ID and a project ID. When a user (of admin level) creates an activity they select from a drop down menu a project. Here is the select query to draw up appropriate values: $sql = "SELECT usersprojects_tb.projectid, projects.projectname FROM projects INNER JOIN usersprojects on projects.projectid = usersprojects.projectid WHERE usersprojects.userid = '".$_SESSION['SESS_USERID']."'"; And for the tag with the dropdown menu, I have this: <?php echo $row['projectname']?> I have tried submitting the form with 'projectid' here instead and the project ID is stored successfully in my activies table. However, the user needs to see the project names (IDs arent exactly user-friendly!) And with 'projectname' as displayed, they can select the names of the available projects (to associate an activity with) but the project ID is not stored, how I link this up, so that when the project name is sent, the ID for this project is stored properly in my activities table. I'm also having the exact same problem with the users drop down. As the admin user selects a user from the drop down to assign the task to. I exactly what I want, but I think I may be using the wrong syntax! Any help is much appreciated. Thanks.

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  • How to nest joins with CakePHP?

    - by Daren Thomas
    I'm trying to behave. So, instead of using following SQL syntax: select * from tableA INNER JOIN tableB on tableA.id = tableB.tableA_id LEFT OUTER JOIN ( tableC INNER JOIN tableD on tableC.tableD_id = tableD.id) on tableC.tableA_id = tableA.id I'd like to use the CakePHP model->find(). This will let me use the Paginator too, since that will not work with custom SQL queries as far as I understand (unless you hardcode one single pagination query to the model which seems a little inflexible to me). What I've tried so far: /* inside tableA_controller.php, inside an action, e.g. "view" */ $this->paginate['recursive'] = -1; # suppress model associations for now $this->paginate['joins'] = array( array( 'table' => 'tableB', 'alias' => 'TableB', 'type' => 'inner', 'conditions' => 'TableB.tableA_id = TableA.id', ), array( 'table' => 'tableC', 'alias' => 'TableC', 'type' => 'left', 'conditions' => 'TableC.tableA_id = TableA.id', 'joins' = array( # this would be the obvious way to do it, but doesn't work array( 'table' => 'tableD', 'alias' => 'TableD', 'type' => 'inner', 'conditions' => 'TableC.tableD_id = TableD.id' ) ) ) ) That is, nesting the joins into the structure. But that doesn't work (CakePHP just ignores the nested 'joins' element which was kind of what I expected, but sad. I have seen hints in comments on how to do subqueries (in the where clause) using a statement builder. Can a similar trick be used here?

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  • Applying for .net jobs as a "self learner"

    - by DeanMc
    Hi All, I have recently started applying for .Net jobs. I currently work in a sales role with a large telco. I found out quite late that I like programming and as such bought my house and made commitments that mean college is not an option. What I would like to know is, is it harder to get a junior job as a self learner? I have gotten a few enquiries regarding my C.V but nothing concrete yet. I try to be involved in projects as I get the chance and tend to put up any worthwhile projects as I develop them. Some examples of my work are: A Xaml lexer and parser: http://www.xlight.mendhak.com A font obfuscation tool: http://www.silverlightforums.com/showthread.php?1516-Font-Obsfucation-Tool-ALPHA A tagger for m4a: http://projectaudiophile.codeplex.com/SourceControl/list/changesets I, of course think that these are great examples of my work but that is my opinion based on self learning. The other query is how much should I actually know? I've never used linked lists but I know that strings are immutable and I understand what that means. I am only touching on T-SQL but I understand things like how properties function in IL (as two standard methods :) ). I suppose I understand a lot of concepts but specific features need some looking up to implement as I may not know the syntax off the top of my head.

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  • Why do pure virtual base classes get direct access to static data members while derived instances do

    - by Shamster
    I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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