pitfalls to avoid - Page 194

How to have NHibernate persist a String.Empty property value as NULL

- by Todd

I have a fairly simple class that I want to save to SQL Server via NHibernate (w/ Fluent mappings). The class is made up mostly of optional string fields. My problem is I default the class fields to string.empty to avoid NullRefExceptions and when NHibernate saves the row to the database each column contains an empty string instead of null. Question: Is there a way for me to get NHibernate to automatically save null when the string property is an empty string? Or do I need to litter my code with if (string.empty) checks?

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Appending target="_blank" to links in an iframe without using <body onload>

- by CincauHangus

I'm trying to change the links in an iframe to load in a new window instead of the iframe itself. Currently I use this code in head: $(document).ready(function() { var oIFrame = document.getElementById("iframeID"); var oDoc = (oIFrame.contentWindow || oIFrame.contentDocument); if(oDoc.document) oDoc = oDoc.document; var links = oDoc.getElementsByTagName("a"); for(var i=0; i<links.length; i++) { links[i].target="_blank"; } }); However, the code above is triggered before the iframe is fully loaded with its contents. I know this code would work if it's triggered in the body onload attribute, but I'd like to avoid that method and implement it in a function or a file instead.

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Download and replace Android resource files

- by Casebash

My application will have some customisation for each company that uses it. Up until now, I have been loading images and strings from resource files. The idea is that the default resources will be distributed with the application and company specific resources will be loaded from our server after they click on a link from an email to launch the initialisation intent. Does anyone know how to replace resource files? I would really like to keep using resource files to avoid rewriting a lot of code/XML. I would distribute the application from our own server, rather than through the app store, so that we could have one version per company, but unfortunately this will give quite nasty security warnings that would concern our customers.

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Diamonds Are Forever. Services Are Not.

- by rayman

Hi, ive read this article by Mark Murphy, while i was looking for a solution to my case. I have a Listener in my system, which suppose to get a UDP trigger times to times from an outside server, ive done this listener as a service. how could i prevent it being shut off by the user? (SDK 1.5), i`am working for a company which create cell phones, and we spread the device with this Listener. as soon as the listener goes off our systems will be terminated any idea for this scenario? *i`am already aware to the face, that the system could also take it off, but this case will be easier to handle and avoid. thanks, ray.

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Measuring the time to create and destroy a simple object

- by portoalet

From Effective Java 2nd Edition Item 7: Avoid Finalizers "Oh, and one more thing: there is a severe performance penalty for using finalizers. On my machine, the time to create and destroy a simple object is about 5.6 ns. Adding a finalizer increases the time to 2,400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers." How can one measure the time to create and destroy an object? Do you just do: long start = System.nanoTime(); SimpleObject simpleObj = new SimpleObject(); simpleObj.finalize(); long end = System.nanoTime(); long time = end - start;

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How to enforce lazy loading of entities on certain conditions

- by Samuel

We have an JPA @Entity class (say User) which has a @ManyToOne reference (say Address) loaded using the EAGER option which in turn loads it's own @ManyToOne fields (say Country) in a EAGER fashion. We use the EntityQuery interface to count the list of User's based on a search criteria, during such a load all the @ManyToOne fields which have been marked as EAGER get loaded. But in order to perform a EntityQuery.resultCount(), I actually don't need to load the @ManyToOne fields. Is there a way to prevent loading of the EAGER fields in such cases so that we can avoid the unnecessary joins?

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Is there any way to store full size image returned from camera activity in internal memory ?

- by SimpleGuy

I am using Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); intent.putExtra(MediaStore.EXTRA_OUTPUT,Uri.fromFile(externalFileObj)); intent to call default camera activity. To get full image you need to specify intent.putExtra(). But this always requires URI that works only for external storage files. I tried to create a temp.jpg image in internal memory and pass its URI Uri.fromFile(new File(getFilesDir() + "/temp.jpg")); but the camera activity won't return back after the image is captured. So there is no way to get Full size image from default camera application in our activity without using any external storage ? Assuming that the device do not have SD card or currently in use is there no way I can avoid using it ? Yes I know we can create our own camerapreview surface but I want to use the default camera application as it is natural with many more options. Thanks.

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Does ASP.NET Make Request Scheduling Decisions Based Upon SessionID?

- by Mike Murphy

I know that a properly implemented SessionStateStoreProvider maintains an exclusive lock on session data for the duration of a request. However, considering that multiple requests could arrive simultaneously (e.g. via IFRAMEs) all but one would be able to make forward progress. All the other requests would block for a bit and reduce the number of worker threads available during that time. It seems if ASP.NET "peeked" at the session IDs on the requests early on, it could avoid running requests simultaneously that were on the same session. This would improve throughput under load for pages that didn't want to give up using IFRAMEs. This seems plausible enough that it might be true.

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MVC best practice when adding functions to controller?

- by Patrick

Hi I'm writing a function in my controller; this is supposed to take in a form, process it, register the user in DB, send a confirmation email etc etc. to avoid this function to be too cluttered, I was thinking of calling some sub-functions (eg: function registration() { //process form.. _insertInDb($formdata) _send_mail($address); //load confirmation view.. } function _send_mail($to) { //code here } function _insertInDb($formdata) { //other code here... } I'm not sure whether writing all the functions in the controller would be best practice -maybe I should insert all 'supporting' function (eg send_mail and insertInDb in this example) in another file and then import them? This would probably make the controller much more readable.. what's your view?

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How do you compose DataTemplates / link to a child datatemplate in WPF?

- by Gishu

Here's the problem. Given a large/intricate datatemplate A, which has 3 sections - General, Properties, Misc. Imagine 3 grids for each. Now I need to reuse the Properties section of the above Datatemplate in another place. Reasons: To avoid redundancy + ensure that further updates to the datatemplate are applied identically to all usages. So I guess what I am asking for is an ability to slot in a link to a child DataTemplate in a parent Datatemplate. What's the best way to go about this ? I found one way to do this.. but I'm not sure if its the right way or the best.. Posting it as an answer below so that it can be rated.

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C# - Why can't I enforce derived classes to have parameterless constructors?

- by FrisbeeBen

I am trying to do the following: public class foo<T> where T : bar, new { _t = new T(); private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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Fusion Table Layer Caching issue

- by user1854791

I have created a series of fusion table layers and apply filtering to one of the layers in response to checkbox click events. The base layer of the map contains a gradient applied over county boundaries. When the base layer is unchecked, the filtered layer loses it's styling. I have added unique timestamps to all queries to avoid caching, however I get the feeling that these image tiles are still be cached for this situation. Is there any way to force the google fusion tables api to invalidate a cached image? Test site here: http://map.inquestmarketing.com/new.html Unchecking the Other - Consumer Prospects checkbox reproduces the issue. This is a pure client app, all of the source is in the single page.

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How to match the word in jquery

- by Mirage

I have the image and i am fade in and fade out the image on click. But i want that if the same is present then it should not fadein/fadeout. My jquery code is switch(current_id) { case 'l1': $("#left_img img").fadeOut(500, function() { $(this).attr("src","rrr.gif").load( function() { $(this).fadeIn(500); }); }); break; case 'l3': $("#left_img img").fadeOut(500, function() { $(this).attr("src","cc1.gif").load( function() { $(this).fadeIn(500); }); }); break; If i click on link 1 then image A appears with fade effect. but if i click again link 1 agan , then again i see fade effect . Is there any way i can avoid that if same link is clicked again

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Optimal way to store and pass a date to Javascript

- by user1493115

I need to store a date-time value in MySQL and subsequently display it on a webpage. Due to its flexibility I usually chose to store a Unix timestamp in the database and convert it with PHP's date() to the desired format. This time however I would like to use MySQL's datetime field (mostly due to 2038) and apply the browser's timezone (hence I cannot simply format it on the server and pass the string to the client). I thought of storing the date as UTC datetime in the database and send it as well-defined format to the client, where it will be further processed. Here I would like to avoid a Unix timestamp but everything else might add additional overhead in processing. Is there any best practice as far as date processing is concerned in a MySQL, PHP, JQuery environment? Thanks.

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Trouble creating a makefile

- by catia

Hi everyone! I'm having some trouble making a Makefile. Write now I just compile everything every time. Although, the professor is ok with that, I do want to get it working faster and to avoid unnecessary compiling. Here's what I have. FILES= p6.cpp SetIter.cpp Node.cpp Set.cpp CFLAGS= -ansi -pendantic -Wall -Wextra CC= g++ MakePg6: p6.cpp SetIter.cpp Node.cpp Set.cpp $(CC) $(CFLAGS) $(FILES) -o pg6 Node.cpp - node class Set.cpp - uses nodes. Friend of Node. SetIter.cpp - gets a set and uses a pointer to iterator through I'm confused with some of the depencies arising from the friends thing and the point of lib.o being included in the Makefile as some sites have. Any help is greatly appreciated. Thanks in advance.

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sqrt(int_value + 0.0) ? The point?

- by Earlz

Hello, while doing some homework in my very strange C++ book, which I've been told before to throw away, had a very peculiar code segment. I know homework stuff always throws in extra "mystery" to try to confuse you like indenting 2 lines after a single-statement for-loop. But this one I'm confused on because it seems to serve some real-purpose. basically it is like this: int counter=10; ... if(pow(floor(sqrt(counter+0.0)),2) == counter) ... I'm interested in this part especially: sqrt(counter+0.0) Is there some purpose to the +0.0? Is this the poormans way of doing a static cast to a double? Does this avoid some compiler warning on some compiler I do not use? The entire program printed the exact same thing and compiled without warnings on g++ whenever I left out the +0.0 part. Maybe I'm not using a weird enough compiler?

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The underlying connection was closed when using a WSDL web service

- by joshlrogers

I am trying to consume this WSDL service: Transit Time Service I successfully connect and get a response the first time but on subsequent calls I receive the exception: The underlying connection was closed: A connection that was expected to be kept alive was closed by the server. I overrode the GetWebRequest in the reference.cs file as such: protected override System.Net.WebRequest GetWebRequest(Uri uri) { HttpWebRequest webRequest = (HttpWebRequest)base.GetWebRequest(uri); webRequest.KeepAlive = false; return webRequest; } This hasn't yielded any improvement. I am at a loss as to what options I have now, does anyone have any other ideas that I could try so that I may avoid this error? Thanks in advance! Josh

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GUID.TryParse() ?

- by Jack Marchetti

Obviously there is no public GUID.TryParse() in .NET CLR 2.0. So, I was looking into regular expressions [aka googling around to find one] and each time I found one there was a heated argument in the comments section about RegEx A doesn't work, use RegEx B. Then someone would write Regex C yadda yadda So anyway, What I decided to do was this, but I feel bad about it. public static bool IsGuid (string possibleGuid) { try { Guid gid = new Guid(possibleGuid); return true; } catch (Exception ex) { return false; } } Obviously I don't really like this since it's been drilled into me since day one to avoid throwing exceptions if you can defensibly code around it. Does anyonek now why there is no public Guid.TryParse() in the .NET Framework? Does anyone have a real Regular Expression that will work for all GUIDs?

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Dynamic proxies to auto-save models

- by atomman

I'm trying to make some auto-magic happen in java using proxies to track objects and saving them when a set* method is called. I started of using java's built in Proxy, and everything works just fine, but from what I can understand I need a interface for every model, which is something that I'm trying to avoid. This is where CGLIB comes in, it allows me to create proxies of my models without the use of interfaces. BUT, how can I now retrieve the original object, the one I am trying to save? The optimal solution to be would be something like the EntityManager interface used by hibernate, where you keep your original object, but it is still tracked.

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Import data from an SSRS report via SSIS package

- by Chris

First, I ask that you not ask 'why.' In the famous words of Tennyson "Ours is not to reason why. Ours is but to do and die." It's one of those, "This is what you have, deal with it." situations. The source data comes from SSRS report. The goal is to load the data into a database via SSIS. The hopeful goal is to avoid human intervention in having to download the SSRS report into Excel or CSV. There will be complex SSIS processing from there on out. Any suggestions are humbly appreciated.

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Cakephp ajax Autocomplete not working

- by Vijay Kumbhar

Hello All, I am using ajax autocomplete in my application, but it is not giving the output. Ajax request to the desired function goes but it is not giving back any response, it is blank. I am also using jquery but it is used for other effects. i added jquery no conflict to avoid the prototype & jquery conflicts. I have tried other ajax helper methods like obeserverfield, it is working fine & returning the proper response, but when i use autocomplete it fails Can anybody help me ..........

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How to organize Windows Phone code base to target both 7.x and 8 platforms

- by ljubomir

I took over a Windows Phone project which was previously targeting WP 7.1 platform, and with the recent announcement of the new platform it should target WP 8 as well. My VS 2010 solution consists on several projects (Data access, Model, Tests and WP7 client app) and i am wandering on how to include support for WP8. I have to note that the code-base is not compatible with WP8, due to usage of Toolkit controls and other 3rd party libraries targeted for WP7.1 specifically. Also there is another problem with the Visual Studio versions - WP7.1 can work with VS 2010, but WP8 requires VS 2012. Should i move the whole code-base to VS 2012? Any good advice on how to organize code-base in a most meaningful way in order to avoid duplication and possible painful maintenance? I am thinking between one solution - multiple projects vs. multiple solutions - reusable projects approach. Code duplication (like two separate folders/solutions) should be the least possible approach (fallback).

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Three boolean values saved in one tinyint

- by Casper

Hello, probably a simple question but I seem to be suffering from programmer's block. :) I have three boolean values: A, B, and C. I would like to save the state combination as an unsigned tinyint (max 255) into a database and be able to derive the states from the saved integer. Even though there are only a limited number of combinations, I would like to avoid hard-coding each state combination to a specific value (something like if A=true and B=true has the value 1). I tried to assign values to the variables so (A=1, B=2, C=3) and then adding, but I can't differentiate between A and B being true from i.e. only C being true. I am stumped but pretty sure that it is possible. Thanks

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Linq to SQL inheritance and Table per Class - approach needed for multiple roles

- by Ash Machine

I am using L2S and an inheritance model for mapping Persons against certain roles. Guy Burstein's excellent blog post explains how to accomplish this: http://blogs.microsoft.co.il/blogs/bursteg/archive/2007/10/01/linq-to-sql-inheritance.aspx However, I have a specific case where a Person has multiple roles. For example 'Jane Doe' is a Contact and a Programmer. In this model, she would need two rows in the People table, one as Contact (PersonType = 1) and one as Programmer (PersonType = 3). If she changes her last name, and that update happens in her role as Contact, I would need to change all instances of 'Jane Doe' to reflect the name change everywhere. What sort of best approach (improved data structure) could be used to change last name within all roles? Finally, I am hoping to avoid overriding each general form update events to include all instances, but that may be the only way. Any suggestions or approaches appreciated.

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NoneType has no attribute Append

- by Rosarch

I'm new to Python. I can't understand why a variable is None at a certain point in my code: class UsersInRoom(webapp.RequestHandler): def get(self): room_id = self.request.get("room_id") username = self.request.get("username") UserInRoom_entities = UserInRoom.gql("WHERE room = :1", room_id).get() if UserInRoom_entities: for user_in_room in UserInRoom_entities: if user_in_room.username == username: user_in_room.put() # last_poll auto updates to now whenenever user_in_room is saved else: user_in_room = UserInRoom() user_in_room.username = username user_in_room.put() UserInRoom_entities = [] UserInRoom_entities.append(user_in_room) // error here # name is `user_at_room` intead of `user_in_room` to avoid confusion usernames = [user_at_room.username for user_at_room in UserInRoom_entities] self.response.out.write(json.dumps(usernames)) The error is: Traceback (most recent call last): File "C:\Program Files\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 507, in __call__ handler.get(*groups) File "path\to\chat.py", line 160, in get AttributeError: 'NoneType' object has no attribute 'append' How is this possible? I'm setting UserInRoom_entities = [] immediately before that call. Or is something else the None in question?

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- by Todd

- by CincauHangus

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- by portoalet

- by Samuel

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- by Mike Murphy

- by Patrick

- by Gishu

- by FrisbeeBen

- by user1854791

- by Mirage

- by user1493115

- by catia

- by Earlz

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- by atomman

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