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  • OptimisticLockException in inner transaction ruins outer transaction

    - by Pace
    I have the following code (OLE = OptimisticLockException)... public void outer() { try { middle() } catch (OLE) { updateEntities(); outer(); } } @Transactional public void middle() { try { inner() } catch (OLE) { updateEntities(); middle(); } @Transactional public void inner() { //Do DB operation } inner() is called by other non-transactional methods which is why both middle() and inner() are transactional. As you can see, I deal with OLEs by updating the entities and retrying the operation. The problem I'm having is that when I designed things this way I was assuming that the only time one could get an OLE was when a transaction closed. This is apparently not the case as the call to inner() is throwing an OLE even when the stack is outer()->middle()->inner(). Now, middle() is properly handling the OLE and the retry succeeds but when it comes time to close the transaction it has been marked rollbackOnly by Spring. When the middle() method call finally returns the closing aspect throws an exception because it can't commit a transaction marked rollbackOnly. I'm uncertain what to do here. I can't clear the rollbackOnly state. I don't want to force create a transaction on every call to inner because that kills my performance. Am I missing something or can anyone see a way I can structure this differently? EDIT: To clarify what I'm asking, let me explain my main question. Is it possible to catch and handle OLE if you are inside of an @Transactional method? FYI: The transaction manager is a JpaTransactionManager and the JPA provider is Hibernate.

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  • are custom classes imported API included in .class files?

    - by kyrogue
    i have a question, i have a custom class which imports java.sql.; and i am creating a jsp page, in the jsp page, i did a page import of the custom class , however when i tried to call my custom class database methods it cant work. only when i did a page import of java.sql. did it work. so are custom classes imported API included in .class files? An error occurred at line: 6 in the jsp file: /resetpw.jsp Statement cannot be resolved to a type 3: 4: <% 5: db.connect(); 6: Statement stmt = db.getConnection().createStatement(); 7: ResultSet rs = stmt.executeQuery("SELECT * FROM created_accounts"); 8: 9: An error occurred at line: 7 in the jsp file: /resetpw.jsp ResultSet cannot be resolved to a type 4: <% 5: db.connect(); 6: Statement stmt = db.getConnection().createStatement(); 7: ResultSet rs = stmt.executeQuery("SELECT * FROM created_accounts"); 8: 9: 10: Stacktrace: org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:93) org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:330) org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:451) org.apache.jasper.compiler.Compiler.compile(Compiler.java:319) org.apache.jasper.compiler.Compiler.compile(Compiler.java:298) org.apache.jasper.compiler.Compiler.compile(Compiler.java:286) org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:565) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:309) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:308) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:259) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) note The full stack trace of the root cause is available in the Apache Tomcat/5.5.31 logs. edited. added what error will come up if i did not do a page import of java.sql.*;

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  • Strongly Typed DataSet column requires custom type to implement IXmlSerializable?

    - by Phil
    I have a strongly typed Dataset with a single table with three columns. These columns all contain custom types. DataColumn1 is of type Parent DataColumn2 is of type Child1 DataColumn3 is of type Child2 Here is what these classes look like: [Serializable] [XmlInclude(typeof(Child1)), XmlInclude(typeof(Child2))] public abstract class Parent { public int p1; } [Serializable] public class Child1 :Parent { public int c1; } [Serializable] public class Child2 : Parent { public int c1; } now, if I add a row with DataColumn1 being null, and DataColumns 2 and 3 populated and try to serialize it, it works: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(null, new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Works! } However, if I try to add a value to DataColumn1, it fails: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(new Child1(), new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Fails! } Here is the Exception: "Type 'WindowsFormsApplication4.Child1, WindowsFormsApplication4, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not implement IXmlSerializable interface therefore can not proceed with serialization." I have also tried using the XmlSerializer to serialize the dataset, but I get the same exception. Does anyone know of a way to get around this where I don't have to implement IXmlSerializable on all the Child classes? Alternatively, is there a way to implement IXmlSerializable keeping all default behavior the same (ie not having any class specific code in the ReadXml and WriteXml methods)

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  • Ruby TypeErrors involving `expected Data`

    - by Kenny Peng
    I've ran into situations where I have gotten these expected Data errors before, but they have always pointed to ActiveRecord not playing well with other libraries in the past. This piece of code: def load(kv_block, debug=false) # Converts a string block to a Hash using split kv_map = StringUtils.kv_array_to_hash(kv_block) # Loop through each key, value kv_map.each do |mem,val| # Format the member from camel case to underscore member = mem.camel_to_underscore() # If the object includes a method to set the key (i.e. the key # is a member of self), invoke the method, setting the value of # the member) if self.methods.include?(member.to_set_method_name()) then # Exception thrown here self.send(member.to_set_method_name(), val) # Else, check for the same case, this time for an instance variable elsif self.instance_variable_defined?(member.to_instance_var_name()) self.instance_variable_set(member.to_instance_var_name(), val) # Else, complain that the object doesn't understand the key with # respect to its class definition. else raise ArgumentError, "I don't know what to do with #{member}. #{self.class} does not have a member or function called #{member}" end end end produces the error wrong argument type #<Class:0x11a02088> (expected Data) (TypeError) in the each loop on the first if test. I've inspected a post-mortem debugging instance using rdebug, and running that line manually, it works without a hitch. Has anyone seen this error before and what's been your solution to it? I used to think it was ActiveRecord and other gems stomping on each other's definitions, but I removed any references to ActiveRecord and this still occurs.

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  • How to implement a 'safe' periodical executer without using the Rails helpers?

    - by Robbie
    I am very new to Ruby on Rails and was never really big on writing JavaScript, so the built in helpers were like a tiny silce of heaven. However I have recently learned that using the helper methods creates "obtrusive javascript" so I am doing a tiny bit of refactoring to get all this messy code out of my view. I'm also using the Prototype API to figure out what all these functions do. Right now, I have: <%= periodically_call_remote(:url => {:action => "tablerefresh", :id => 1 }, :frequency => '5', :complete => "load('26', 'table1', request.responseText)")%> Which produces: <script type="text/javascript"> //<![CDATA[ new PeriodicalExecuter(function() {new Ajax.Request('/qrpsdrail/grids/tablerefresh/1', {asynchronous:true, evalScripts:true, onComplete:function(request){load('26', 'table1', request.responseText)}, parameters:'authenticity_token=' + encodeURIComponent('dfG7wWyVYEpelfdZvBWk7MlhzZoK7VvtT/HDi3w7gPM=')})}, 5) //]]> </script> My concern is that the "encodeURIComponent" and the presence of "authenticity_token" are generated by Rails. I'm assuming these are used to assure the validity of a request. (Ensuring a request comes from a currently active session?) If that is the case, how can I implement this in application.js 'safely'? It seems that the built in method, although obtrusive, does add some beneficial security. Thanks, in advance, to all who answer.

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  • ASP:GridView does not show data with ObjectdataSource

    - by Kashif
    I have been trying to bind a DataGrid with ObjectDataSource having custom paging but no output is display on my usercontrol. Here is the code I am using <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="LeadId" DataSourceID="dsBuyingLead1" AllowPaging="True"> <Columns> <asp:BoundField DataField="Subject" HeaderText="Subject" ReadOnly="True" /> <asp:BoundField DataField="ExpiryDate" HeaderText="ExpiryDate" ReadOnly="True" /> </Columns> </asp:GridView> <asp:ObjectDataSource ID="dsBuyingLead1" runat="server" EnablePaging="True" DataObjectTypeName="Modules.SearchBuyingLeadInfo" OldValuesParameterFormatString="original_{0}" SelectMethod="GetAllBuyingLeads" StartRowIndexParameterName="startRow" MaximumRowsParameterName="maximumRows" SelectCountMethod="GetAllBuyingLeadsCount" TypeName="Modules.SearchController"> <SelectParameters> <asp:QueryStringParameter Name="searchText" QueryStringField="q" Type="String" /> </SelectParameters> </asp:ObjectDataSource> Here are my methods from SearchController class: [DataObjectMethod(DataObjectMethodType.Select)] public static long GetAllBuyingLeadsCount(string searchText) { return DataProvider.Instance().GetAllBuyingLeadsCount(searchText); } [DataObjectMethod(DataObjectMethodType.Select)] public static List<SearchBuyingLeadInfo> GetAllBuyingLeads (string searchText, int startRow, int maximumRows) { List<SearchBuyingLeadInfo> l = CBO.FillCollection<SearchBuyingLeadInfo> ( DataProvider.Instance() .GetAllBuyingLeadswithText(searchText, startRow, maximumRows) ); return l; } Where SearchBuyingLeadInfo is my Data Access Object class I have verified by setting up break points that both GetAllBuyingLeadsCount and GetAllBuyingLeads return non-zero values but unfortunately nothing is displayed on the grid. Only the column headers are displayed. Can anyone tell me what am I missing?

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  • Componentizing complex functionality in an MVC web app

    - by NXT
    Hi Everyone, This is question about MVC web-app architecture, and how it can be extended to handle componentizing moderately complex units of functionality. I have an MVC style web-app with a customer facing credit card charge page. I've been asked to allow the admins to enter credit card payments as well, for times when credit cards are taken over the phone. The customer facing credit card charge section of the website is currently it's own controller, with approximately 3 pages and a login. That controller is responsible for: Customer login credential authentication Credit card data collection Calling a library to do the actual charge. reporting the results to the user. I would like to extract the card data collection pages into a component of some kind so that I can easily reuse the code on the admin side of the app. Right now my components are limited to single "view" pages with PHP style embedded Perl code. This is a simple, custom MVC framework written in Perl. Right now, controllers are called directly from the framework to service web requests. My idea is to allow controllers to be called from other controllers, so that I can componentize more complex functionality. For simplicity I think I prefer composition over inheritance, even though it will require writing a bunch of pass-through methods (actions). Being Perl, I could in theory do multiple inheritance. I'm wondering if anyone with experience in other MVC web frameworks can comment on how this sort of thing is usually done. Thank you.

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  • jQuery & Prototype Conflict

    - by DPereyra
    Hi, I am using the jQuery AutoComplete plugin in an html page where I also have an accordion menu which uses prototype. They both work perfectly separately but when I tried to implement both components in a single page I get an error that I have not been able to understand. uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMViewCSS.getComputedStyle]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: file:///C:/Documents and Settings/Administrator/Desktop/website/js/jquery-1.2.6.pack.js :: anonymous :: line 11" data: no] I found out the file conflicting with jQuery is 'effects.js' which is used by the accordion menu. I tried replacing this file with a newer version but newer seems to break the accordion behavior. My guess is that the 'effects.js' file used in the accordion was modified to obtain the accordion demo output. I also tried using the overriding methods jQuery needs to avoid conflict with other libraries and that did not work. I obtained the accordion demo from the following site: http://www.stickmanlabs.com/accordion/ And the jQuery AutoComplete can be obtained from: http://docs.jquery.com/Plugins/Autocomplete#Setup Has any one else experienced this issue? Thanks.

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  • Iphone SDK quesiton: How to make a Drawing method in a View class work using CGContextRef?

    - by SimpleCode
    I have these 2 methods in the View class. the drawRect method always gets called when the view is initalized. But i can't get the drawLine method to work. It doesn't do anything when it gets called. Am i supposed to deal with cgimagecontext or something like that? please help!! (void)drawRect:(CGRect)rect { // Drawing code // Drawing code CGContextRef contextRef = UIGraphicsGetCurrentContext(); //CGContextSetRGBFillColor(contextRef, 0, 0, 255, 1); CGContextSetRGBStrokeColor(contextRef, 0, 0, 0, 1); CGContextSetLineWidth(contextRef, 5.0); CGContextBeginPath(contextRef); CGContextMoveToPoint(contextRef, 0, 0); CGContextAddLineToPoint(contextRef, 320, 480); CGContextStrokePath(contextRef); } -(void)drawLine:(CGPoint)from to:(CGPoint) to { // Drawing code CGContextRef contextRef = UIGraphicsGetCurrentContext(); //CGContextSetRGBFillColor(contextRef, 0, 0, 255, 1); CGContextSetRGBStrokeColor(contextRef, 0, 128, 0, 1); CGContextSetLineWidth(contextRef, 5.0); CGContextBeginPath(contextRef); CGContextMoveToPoint(contextRef, 0, 0); CGContextAddLineToPoint(contextRef, 320, 50); CGContextStrokePath(contextRef); }

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  • I need help understanding how this jQuery filter function works, line-by-line, if possible

    - by user717236
    Here is the HTML: <div> <h3>text</h3> </div> <div> <h3>moretext</h3> </div> <div> <h3>123</h3> </div>?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? Here is the JS: var rv1_wlength = $("div").filter(function() { return $(this).find("h3").filter(function () { return $(this).text() != "123"; }).length; }); var rv1_wolength = $("div").filter(function() { return $(this).find("h3").filter(function () { return $(this).text() != "123"; }); }); var rv2 = $("div").find("h3").filter(function() { return $(this).text() != "123"; }); alert(rv1_wlength.text()); // text // moretext alert(rv1_wolength.text()); // text // moretext // 123 alert(rv2.text());? // textmoretext I don't understand why the first two methods print the elements on each line, whereas the second method concatenates them. "rv2" is a jQuery object. Then, what are the first two (rv1_wlength and rv1_wolength)? Furthermore, I don't understand why the inclusion of the length property makes all the difference in filtering the elements. The second method does nothing, since it returns all the elements. The first method, with the only change being the addition of the length property, correctly filters the elements. I would very much like a line-by-line explanation. I would sincerely appreciate any feedback. Thank you.

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  • Should I Use Anchor, Button Or Form Submit For "Follow" Feature In Rails

    - by James
    I am developing an application in Rails 3 using a nosql database. I am trying to add a "Follow" feature similar to twitter or github. In terms of markup, I have determined that there are three ways to do this. 1) Use a regular anchor. (Github Uses This Method) <a href="/users/follow?target=Joe">Follow</a> 2) Use a button. (Twitter Uses This Method) <button href="/friendships/create/">Follow</button> 3) Use a form with a submit button. (Has some advantages for me, but I haven't see anyone do it yet.) <form method="post" id="connection_new" class="connection_new" action="/users/follow"> <input type="hidden" value="60d7b563355243796dd8496e17d36329" name="target" id="target"> <input type="submit" value="Follow" name="commit" id="connection_submit"> </form> Since I want to store the user_id in the database and not the username, options 1 and 2 will force me to do a database query to get the actual user_id, whereas option 3 will allow me to store the user_id in a hidden form field so that I don't have to do any database lookups. I can just get the id from the params hash on form submission. I have successfully got each of these methods working, but I would like to know what is the best way to do this. Which way is more semantic, secure, better for spiders, etc...? Is there a reason both twitter and github don't use forms to do this? Any guidance would be appreciated. I am leaning towards using the form method since then I don't have to query the db to get the id of the user, but I am worried that there must be a reason the big guys are just using anchors or buttons for this. I am a newb so go easy on me if I am totally missing something. Thanks!

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  • How to find which file is open in eclipse editor without using IEditorPart?

    - by Destructor
    I want to know which file (or even project is enough) is opened in eclipse editor? I know we can do this once we get IEditorPart from doSetInput method, IFile file = ((IFileEditorInput) iEditorPart).getFile(); But I want the name of file without using IEditorPart, how can I do the same? Checking which is the selected file in project explorer is not of much help because, user can select multiple files at once and open all simultaneously and I did not way to distinguish which file opened at what time. Adding more info: I have an editor specified for a particular type of file, now every time it opens, during intializing editor I have some operation to do based on project properties. While initializing editor, I need the file handle (of the one which user opened/double clicked) or the corresponding project handle. I have my editor something this way: public class MyEditor extends TextEditor{ @Override protected void initializeEditor() { setSourceViewerConfiguration(new MySourceViewerConfiguration( CDTUITools.getColorManager(), store, "MyPartitions", this)); } //other required methods @Override protected void doSetInput(IEditorInput input) throws CoreException { if(input instanceof IFileEditorInput) { IFile file = ((IFileEditorInput) input).getFile(); } } } as I have done in the doSetInput() method , I want the file handle(even project handle is sufficient). But the problem is in initializeEditor() function there is no reference to editorInput, hence I am unable to get the file handle. In the source viewer configuration file, I set the code scanners and this needs some project specific information that will set the corresponding rules.

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  • (nested) user controls within a mvp pattern causing sporadic problems

    - by LLEA
    hi everyone, I have a serious problem with nested user controls (UCs) in WinForms while trying to implement the mvp pattern (passive view). The project consists of one model (designed as a singleton) and a set of different presenters with corresponding view interfaces. To avoid one huge view interface and therefore an overloaded main UI, I decided to make use of a set of different UCs. Each UC has one view interface and one presenter that can access the model. But there are nested UCs: meaning that one specialised UC implements sort of a basic UC. The main UI just represents a container for all those UCs. So far, so good (if not, please ask)?! There are two problems that I am facing now (but I guess both are of the same origin): From time to time it is not possible anymore to load the UCs and test them within the Visual Studio 2008 User Control Test Container. The error message just says that a project with an output type of class library cannot be started directly etc. I can "handle" that by unloading all UC projects and reloading them afterwards. (I guess the references to all mvp components and other UCs are then updated). Assuming that the implementation of my mvp pattern is okay and all those UCs are testable within the VS Test Container at a certain time - there is the biggest problem still left: I am not able to add any UC (even the basic and unnested ones) to a simple Form (UI). The error message: error message.jpg Could it be that my basic UC causes all these Problems?! It consists of two simple ComboBoxes and implements a basic presenter and basic view interface. Whenever I add this UC to a different UC the VS designer adds two references to the public getter methods of the UC as resources. I then manually remove those resources from the resx-file and commend the corresponding lines in the designer file. thx in advance

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  • Setting String as Image Source in C#

    - by Dan
    UPDATE: Okay I've changed my code to this: if (appSettings.Contains("image")) { Uri uri = new Uri( (string)appSettings["image"] + ".jpg", UriKind.Absolute); ImageSource imgSource = new BitmapImage(uri); myImage.Source = imgSource; } else { Uri uriDefault = new Uri("default.jpg", UriKind.Absolute); ImageSource imgSourceDefault = new BitmapImage(uriDefault); myImage.Source = imgSourceDefault; } But now I get "Invalid URI: The format of the URI could not be determined". Well I've looked up several methods to fix this in my Windows Phone 7 app but I can't seem to find anything that works. What confuses me is that I've done something just like this before with no problem, so I'm not sure why it's not working. The code causing me the problem is this: if (appSettings.Contains("image")) { myImage.Source = (string)appSettings["image"]; } else { myImage.Source = "default.jpg"; } The error I get is this "Cannot implicitly convert type 'string' to 'System.Windows.Media.ImageSource". The reason this confuses me is because I did this Twitter app tutorial: http://weblogs.asp.net/scottgu/archive/2010/03/18/building-a-windows-phone-7-twitter-application-using-silverlight.aspx , in which you bind the image source directly to a string. So what can I do to remedy this?

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  • Help me clean up this crazy lambda with the out keyword

    - by Sarah Vessels
    My code looks ugly, and I know there's got to be a better way of doing what I'm doing: private delegate string doStuff( PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt ); private bool tryEncryptPassword( doStuff encryptPassword, out string errorMessage ) { ...get some variables... string encryptedPassword = encryptPassword(encrypter, publicKey, privateKey, out salt); ... } This stuff so far doesn't bother me. It's how I'm calling tryEncryptPassword that looks so ugly, and has duplication because I call it from two methods: public bool method1(out string errorMessage) { string rawPassword = "foo"; return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 1 rawPassword, publicKey, privateKey, out salt ), out errorMessage ); } public bool method2(SecureString unencryptedPassword, out string errorMessage) { return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 2 unencryptedPassword, publicKey, privateKey, out salt ), out errorMessage ); } Two parts to the ugliness: I have to explicitly list all the parameter types in the lambda expression because of the single out parameter. The two overloads of EncryptPasswordAndDoStuff take all the same parameters except for the first parameter, which can either be a string or a SecureString. So method1 and method2 are pretty much identical, they just call different overloads of EncryptPasswordAndDoStuff. Any suggestions? Edit: if I apply Jeff's suggestions, I do the following call in method1: return tryEncryptPassword( (encrypter, publicKey, privateKey) => { var result = new EncryptionResult(); string salt; result.EncryptedValue = encrypter.EncryptPasswordAndDoStuff( rawPassword, publicKey, privateKey, out salt ); result.Salt = salt; return result; }, out errorMessage ); Much the same call is made in method2, just with a different first value to EncryptPasswordAndDoStuff. This is an improvement, but it still seems like a lot of duplicated code.

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  • Best way to catch a WCF exception in Silverlight?

    - by wahrhaft
    I have a Silverlight 2 application that is consuming a WCF service. As such, it uses asynchronous callbacks for all the calls to the methods of the service. If the service is not running, or it crashes, or the network goes down, etc before or during one of these calls, an exception is generated as you would expect. The problem is, I don't know how to catch this exception. Because it is an asynchronous call, I can't wrap my begin call with a try/catch block and have it pick up an exception that happens after the program has moved on from that point. Because the service proxy is automatically generated, I can't put a try/catch block on each and every generated function that calls EndInvoke (where the exception actually shows up). These generated functions are also surrounded by External Code in the call stack, so there's nowhere else in the stack to put a try/catch either. I can't put the try/catch in my callback functions, because the exception occurs before they would get called. There is an Application_UnhandledException function in my App.xaml.cs, which captures all unhandled exceptions. I could use this, but it seems like a messy way to do it. I'd rather reserve this function for the truly unexpected errors (aka bugs) and not end up with code in this function for every circumstance I'd like to deal with in a specific way. Am I missing an obvious solution? Or am I stuck using Application_UnhandledException? [Edit] As mentioned below, the Error property is exactly what I was looking for. What is throwing me for a loop is that the fact that the exception is thrown and appears to be uncaught, yet execution is able to continue. It triggers the Application_UnhandledException event and causes VS2008 to break execution, but continuing in the debugger allows execution to continue. It's not really a problem, it just seems odd.

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  • A question about entities, roles and interfaces in Entity Framework 4.

    - by mvole
    Hi, I am an experienced .NET developer but new to EF - so please bear with me. I will use an example of a college application to illustrate my problem. I have these user roles: Lecturer, Student, Administrator. In my code I envisage working with these entities as distinct classes so e.g. a Lecturer teaches a collection of Students. And work with 'is Student' 'TypeOf' etc. Each of these entities share lots of common properties/methods e.g. they can all log onto the system and do stuff related to their role. In EF designer I can create a base entity Person (or User...) and have Lecturer, Student and Administrator all inherit from that. The difficulty I have is that a Lecturer can be an Administrator - and in fact on occasion a Student can be a Lecturer. If I were to add other entities such as Employee and Warden then this gets even more of an issue. I could presumably work with Interfaces so a person could implement ILecturer and IStudent, however I do not see how this fits within EF. I would like to work within the EF designer if possible and I'm working model-first (coding in C#). So any help and advice/samples would be very welcome and much appreciated. Thanks

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  • C# - Advantages/Disadvantages of different implementations for Comparing Objects

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these methods?

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  • How do I use Core Data with the Cocoa Text Input system?

    - by the Joel
    Hobbyist Cocoa programmer here. Have been looking around all the usual places, but this seems relatively under-explained: I am writing something a little out of the ordinary. It is much simpler than, but similar to, a desktop publishing app. I want editable text boxes on a canvas, arbitrarily placed. This is document-based and I’d really like to use Core Data. Now, The cocoa text-handling system seems to deal with a four-class structure: NSTextStorage, NSLayoutManager, NSTextContainer and finally NSTextView. I have looked into these and know how to use them, sort of. Have been making some prototypes and it works for simple apps. The problem arrives when I get into persistency. I don't know how to, by way of Cocoa Bindings or something else, store the contents of NSTextStorage (= the actual text) in my managed object context. I have considered overriding methods pairs like -words, -setWords: in these objects. This would let me link the words to a String, which I know how to store in Core Data. However, I’d have to override any method that affects the text - and that seems a little much. Thankful for any insights.

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  • Managing inverse relationships without CoreData

    - by Nathaniel Martin
    This is a question for Objective-J/Cappuccino, but I added the cocoa tag since the frameworks are so similar. One of the downsides of Cappuccino is that CoreData hasn't been ported over yet, so you have to make all your model objects manually. In CoreData, your inverse relationships get managed automatically for you... if you add an object to a to-many relationship in another object, you can traverse the graph in both directions. Without CoreData, is there any clean way to setup those inverse relationships automatically? For a more concrete example, let's take the typical Department and Employees example. To use rails terminology, a Department object has-many Employees, and an Employee belongs-to a Department. So our Department model has an NSMutableSet (or CPMutableSet ) "employees" that contains a set of Employees, and our Employee model has a variable "department" that points back to the Department model that owns it. Is there an easy way to make it so that, when I add a new Employee model into the set, the inverse relationship (employee.department) automatically gets set? Or the reverse: If I set the department model of an employee, then it automatically gets added to that department's employee set? Right know I'm making an object, "ValidatedModel" that all my models subclass, which adds a few methods that setup the inverse relationships, using KVO. But I'm afraid that I'm doing a lot of pointless work, and that there's already an easier way to do this. Can someone put my concerns to rest?

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  • what use does the javascript forEach method have (that map can't do)?

    - by JohnMerlino
    Hey all, The only difference I see in map and foreach is that map is returning an array and foreach is not. However, I don't even understand the last line of the foreach method "func.call(scope, this[i], i, this);". For example, isn't "this" and "scope" referring to same object and isn't this[i] and i referring to the current value in the loop? I noticed on another post someone said "Use forEach when you want to do something on the basis of each element of the list. You might be adding things to the page, for example. Essentially, it's great for when you want "side effects". I don't know what is meant by side effects. Array.prototype.map = function(fnc) { var a = new Array(this.length); for (var i = 0; i < this.length; i++) { a[i] = fnc(this[i]); } return a; } Array.prototype.forEach = function(func, scope) { scope = scope || this; for (var i = 0, l = this.length; i < l; i++) func.call(scope, this[i], i, this); } Finally, are there any real uses for these methods in javascript (since we aren't updating a database) other than to manipulate numbers like this: alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript. Thanks for any reply.

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  • How to overcome the programmer's block ?

    - by Nicolas Dorier
    How do you do when, during the development of your application, you can't decide yourself what to do next. You have no problem technically speaking, you have no problem to write clean code BUT you have a problem to decide yourself on what to code now. And you spend time thinking and thinking again on your design, in the car, in the shower, and you cannot write a single line of code... I think we call this "analysis paralysis". I hate being in this state ! How can you avoid this ? How do you do to not fall in this state ? I think this occurs when we are writting a big chunk of code with no visible improvement, but I'm not sure... UPDATE Like some of you said, this problem is also what we call the "programmer's block" (analogy with the writer's block). Doing some TDD doesn't help because I'm stuck, I can't decide myself what class to code, what methods to put inside (even a name of method). Though I admit that it helps to break a big chunk of code into smaller ones. Like Talesh said my head becomes full of "what-if".

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  • Drawing graphics on top of a JButton

    - by trinth
    I have a situation wherein I have a bunch of JButtons on a GridLayout. I need each of the JButtons to have: a background image (but retain the ability to keep the default button look if needed) custom graphics drawn on top by other classes I have no trouble with the background image, since I am using setIcon() but I am having problems drawing things on top of the background. At one point I was able to draw on top of the button, but after the button was clicked, the drawings disappeared. How can make the button keep this drawing state? Basically, I need a way for my JButtons to have public methods that would allow another class to draw anything on it such as: public void drawSomething() { Graphics g = this.getGraphics(); g.drawOval(3,2,2,2); repaint(); } or public Graphics getGraphics() { return this.getGraphics(); } then another class could do this: button.getGraphics().drawSomething(); The latter is more what I am looking for but the first is equally useful. Is there any way to go about this? Also, overriding the parent class method paintComponent() doesn't help since I need each button to have different graphics.

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  • calling java script function then C# function after clicking ASP.NET button

    - by Eyla
    I have this serious: I have ASP.NET page, This page contents Update panel with ASP.NET control. I have Java script function to do validation so when I click the button I will use onclientclick to call the java function to do the validation and after this one done should call then event click button function from code behind. I tried vew methods but they did not work for me. here is sample of my code that after I click the button onclientclick will call the java script function for validation and if the validation is OK should call onclick event. .................... java script function ........................ <script type="text/javascript" > function add(){ if (tag == trye) { document.getElementById('<%=btnInfor.ClientID%>').click(); alert("DataAdded") } else { alert("Requiered Field Missing.") return false; } } </script> ..................... ASP.NET button ................... <asp:Button ID="btnInfor" runat="server" Text="Add Information" Style="position: absolute; top: 1659px; left: 433px;" onclientclick="JavaScript: return myAdd()" /> .................... code behind in C# ...................... protected void btnInfor_Click(object sender, EventArgs e) { \\mycode }

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  • array of structures, or structure of arrays?

    - by Jason S
    Hmmm. I have a table which is an array of structures I need to store in Java. The naive don't-worry-about-memory approach says do this: public class Record { final private int field1; final private int field2; final private long field3; /* constructor & accessors here */ } List<Record> records = new ArrayList<Record>(); If I end up using a large number ( 106 ) of records, where individual records are accessed occasionally, one at a time, how would I figure out how the preceding approach (an ArrayList) would compare with an optimized approach for storage costs: public class OptimizedRecordStore { final private int[] field1; final private int[] field2; final private long[] field3; Record getRecord(int i) { return new Record(field1[i],field2[i],field3[i]); } /* constructor and other accessors & methods */ } edit: assume the # of records is something that is changed infrequently or never I'm probably not going to use the OptimizedRecordStore approach, but I want to understand the storage cost issue so I can make that decision with confidence. obviously if I add/change the # of records in the OptimizedRecordStore approach above, I either have to replace the whole object with a new one, or remove the "final" keyword. kd304 brings up a good point that was in the back of my mind. In other situations similar to this, I need column access on the records, e.g. if field1 and field2 are "time" and "position", and it's important for me to get those values as an array for use with MATLAB, so I can graph/analyze them efficiently.

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