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• Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

  - by aklin81

  I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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• Two objects with dependencies for each other. Is that bad?

  - by Kasper Grubbe

  Hi SO. I am learning a lot about design patterns these days. And I want to ask you about a design question that I can't find an answer to. Currently I am building a little Chat-server using sockets, with multiple Clients. Currently I have three classes. Person-class which holds information like nick, age and a Room-object. Room-class which holds information like room-name, topic and a list of Persons currently in that room. Hotel-class which have a list of Persons and a list of Rooms on the server. I have made a diagram to illustrate it (Sorry for the big size!): http://i.imgur.com/Kpq6V.png I have a list of players on the server in the Hotel-class because it would be nice to keep track of how many there are online right now (Without having to iterate through all of the rooms). The persons live in the Hotel-class because I would like to be able to search for a specific Person without searching the rooms. Is this bad design? Is there another way of achieve it? Thanks.

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• Game architecture: modeling different steps/types of UI

  - by Sander

  I have not done any large game development projects, only messed around with little toy projects. However, I never found an intuitive answer to a specific design question. Namely, how are different types/states of UI modeled in games? E.g. how is a menu represented? How is it different from a "game world" state (let's use an FPS as an example). How is an overlaid menu on top of a "game world" modeled? Let's imagine the main loop of a game. Where do the game states come into play? It it a simple case-by-case approach? if (menu.IsEnabled) menu.Process(elapsedTime); if (world.IsEnabled) world.Process(elapsedTime); if (menu.IsVisible) menu.Draw(); if (world.IsVisible) world.Draw(); Or are menu and world represented somewhere in a different logic layer and not represented at this level? (E.g. a menu is just another high-level entity like e.g. player input or enemy manager, equal to all others) foreach (var entity in game.HighLevelEntities) entity.Process(elapsedTime); foreach (var entity in game.HighLevelEntities) entity.Draw(elapsedTime); Are there well-known design patterns for this? Come to think of it, I don't know any game-specific design patterns - I assume there are others, as well? Please tell me about them.

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• Where can a self-teacher learn general good programming habits and conventions?

  - by lucid

  A few mistakes and general childishness in early adulthood have left me in a situation where I work a menial job, with no possibility (in the near future) of attending school. I aspire to one day work in the programming field (gaming specifically), after proving myself on the indie end of things. I've gotten very confident in C++, java, and python, and I find I'm able to solve any problem I want either from previous experience, or from scouring the web for help. The solutions work, and with each attempt they become more readable, maintainable, and extensible. But this is because I'm learning from mistakes and bad programming and design habits I feel I might have avoided with actual schooling. General tips like: "if it's hard to read or getting long, or you're writing it twice, it should be in one or more functions." or "design all your classes before you start coding, so you don't have to rewrite classes later when you discover an unforeseen dependency" Is there a good book or website for learning general good programming practices and design habits? Also, naming and format conventions. I realize sometimes development houses have their own conventions, but things like "Classes in python usually have the first letter of each word capitalized". I'd like to be able to show some source code to a potential employer, and be prepared when for what's expected on a team. Is there some central database of naming and formatting conventions somewhere? Also, feel free to give any thoughts on whether or not the self-teach, garner some indie sales, use them as your resume' route is realistic

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• What's the best way to store Logon User information for Web Application?

  - by Morgan Cheng

  I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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• C++ Matrix class hierachy

  - by bpw1621

  Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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• How to understand existing projects

  - by John

  Hi. I am a trainee developer and have been writing .NET applications for about a year now. Most of the work I have done has involved building new applications (mainly web apps) from scratch and I have been given more or less full control over the software design. This has been a great experience however, as a trainee developer my confidence about whether the approaches I have taken are the best is minimal. Ideally I would love to collaborate with more experienced developers (I find this the best was I learn) however in the company I work for developers tend to work in isolation (a great shame for me). Recently I decided that a good way to learn more about how experienced developers approach their design might be to explore some open source projects. I found myself a little overwhelmed by the projects I looked at. With my level of experience it was hard to understand the body of code I faced. My question is slight fuzzy one. How do developers approach the task of understanding a new medium to large scale project. I found myself pouring over lots of code and struggling to see the wood for the trees. At any one time I felt that I could understand a small portion of the system but not see how its all fits together. Do others get this same feeling? If so what approaches do you take to understanding the project? Do you have any other advice about how to learn design best practices? Any advice will be very much appreciated. Thank you.

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• Implementing search functionality with multiple optional parameters against database table.

  - by quarkX

  Hello, I would like to check if there is a preferred design pattern for implementing search functionality with multiple optional parameters against database table where the access to the database should be only via stored procedures. The targeted platform is .Net with SQL 2005, 2008 backend, but I think this is pretty generic problem. For example, we have customer table and we want to provide search functionality to the UI for different parameters, like customer Type, customer State, customer Zip, etc., and all of them are optional and can be selected in any combinations. In other words, the user can search by customerType only or by customerType, customerZIp or any other possible combinations. There are several available design approaches, but all of them have some disadvantages and I would like to ask if there is a preferred design among them or if there is another approach. Generate sql where clause sql statement dynamically in the business tier, based on the search request from the UI, and pass it to a stored procedure as parameter. Something like @Where = ‘where CustomerZip = 111111’ Inside the stored procedure generate dynamic sql statement and execute it with sp_executesql. Disadvantage: dynamic sql, sql injection Implement a stored procedure with multiple input parameters, representing the search fields from the UI, and use the following construction for selecting the records only for the requested fields in the where statement. WHERE (CustomerType = @CustomerType OR @CustomerType is null ) AND (CustomerZip = @CustomerZip OR @CustomerZip is null ) AND ………………………………………… Disadvantage: possible performance issue for the sql. 3.Implement separate stored procedure for each search parameter combinations. Disadvantage: The number of stored procedures will increase rapidly with the increase of the search parameters, repeated code.

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• Eclipc java,writting a program [closed]

  - by ghassar

  I have an important exercise for that i found in the internet please i need help in using eclipc java thanks i have to design, implement, test and document a Java program (a set of classes) for one of the following problem specifications: Problem 1 – Jubilee Estate Agency Property Management System A local Estate Agent would like a prototype system to keep track of properties that are offered for sale. The Estate Agent sells domestic and commercial properties. You will need to define classes that represent the Estate Agency System. You should design your system and the classes that you will need before starting coding. Your system must have a graphical user interface and be designed and developed using the object-oriented principles of the MVC architecture design pattern i.e. the user interface class must be separate from the other classes. The initial basic requirements for the system are as follows: • Include a list of domestic properties for sale that include details of: address, description, selling price, and number of rooms • Include a list of commercial properties for sale that include details of: address, description, selling price, and area in square metres • Enable the properties that are for sale to be viewed on the screen • Allow the customer to select one or more properties to be placed on a ‘viewing list’ so that the properties can be visited in person • Display on the screen the viewing list that shows the details of the properties chosen • Provide a basic search facility to find properties that are for sale in a particular price band and display the results • Enable a property to be marked as sold

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• AWS S3 status code 403 SignatureDoesNotMatch - Check your key and signing method

  - by Matt

  i have checked a rechecked my keys and they are correct but i keep the below Exception whenever i try to upload, can anyone shed some light on this problem? 11-01 09:21:26.331: W/System.err(13934): AmazonS3Exception: Status Code: 403, AWS Service: Amazon S3, AWS Request ID: B97CC81E13D81XXX, AWS Error Code: SignatureDoesNotMatch, AWS Error Message: The request signature we calculated does not match the signature you provided. Check your key and signing method., S3 Extended Request ID: PPieuQpqElIizNBQPc42JwC4WnBkUciCKRT5S4HSftBraeacN8y0lKfsVP9LXXXX 11-01 09:21:26.331: W/System.err(13934): at com.amazonaws.http.AmazonHttpClient.handleErrorResponse(AmazonHttpClient.java:659) 11-01 09:21:26.331: W/System.err(13934): at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:330) 11-01 09:21:26.331: W/System.err(13934): at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:182) 11-01 09:21:26.331: W/System.err(13934): at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:3038) 11-01 09:21:26.331: W/System.err(13934): at com.amazonaws.services.s3.AmazonS3Client.putObject(AmazonS3Client.java:1218) 11-01 09:21:26.331: W/System.err(13934): at com.apprssd.capsule.S3UploaderActivity$S3PutObjectTask.doInBackground(S3UploaderActivity.java:165) 11-01 09:21:26.331: W/System.err(13934): at com.apprssd.capsule.S3UploaderActivity$S3PutObjectTask.doInBackground(S3UploaderActivity.java:1) 11-01 09:21:26.331: W/System.err(13934): at android.os.AsyncTask$2.call(AsyncTask.java:287) 11-01 09:21:26.331: W/System.err(13934): at java.util.concurrent.FutureTask.run(FutureTask.java:234) 11-01 09:21:26.341: W/System.err(13934): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 11-01 09:21:26.341: W/System.err(13934): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 11-01 09:21:26.341: W/System.err(13934): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 11-01 09:21:26.341: W/System.err(13934): at java.lang.Thread.run(Thread.java:841) It happens during the below. PutObjectRequest por = new PutObjectRequest( Constants.getDataBucket(), selectedZip.toString(), selectedZip); s3Client.putObject(por);

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• JSF invoke backing bean method and reRender components on ENTER key

  - by Markos Fragkakis

  Hi, I have a datatable with as search fields. I want a method on the backing bean to be invoked when ENTER key is pressed, as well as the DataTable to be re-rendered. My approach so far only works in IE 6, and 7, not in FF. This is the inputText: <h:inputText value="#{applicantProductListBean.applicantNameFilterValue}" id="applicantNameFilterValue" onkeypress="submitByEnter(event)"> </h:inputText> and this is the Javascript method I am invoking: function submitByEnter(e){ if(e.keyCode==13){ // alert("Enter was pressed"); e.returnValue=false; e.cancel=true; document.getElementById("applicantProductListForm:refreshButton").click(); } } As you can see, the Javascript method clicks on the button refresh, which exists on the page: <a4j:commandButton value="Refresh" id="refreshButton" action="#{applicantProductListBean.refreshData}" image="/images/icons/refresh48x48.gif" reRender="table, scroller"> </a4j:commandButton> The refreshData method does not return anything. As said before, this only works in IE 6 and IE 7. Does anyone know why it does not work in FF? An alternative I was considering was HotKey, which can indeed catch the event of ENTER, but it can only invoke Javascript, so it isn't appropriate. Is the proper way to do this via RichFaces or plain JSF? Cheers! UPDATE: Slightly modified the answer by BalusC, the script that works is: if (event.preventDefault) { // Firefox event.preventDefault(); } else { // IE event.returnValue = false; }

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• ASP MVC C#: LINQ Foreign Key Constraint conflicts

  - by wh0emPah

  I'm having a problem with LINQ. I have 2 tables (Parent-child relation) Table1: Events (EventID, Description) Table2: Groups (GroupID, EventID(FK), Description) Now i want to create an Event an and a child. Event e = new Event(); e.Description = "test"; Datacontext.Events.InsertOnSubmit(event) Group g = new Group(); g.Description = "test2"; g.EventID = e.EventID; Datacontext.Groups.InsertOnSubmit(g); Datacontext.SubmitChanges(); When i debug, i can see that after inserting the event. the EventID has gotten a new value (auto increment). But when Datacontext.SubmitChanges(); gets called. I get the following exception "The INSERT statement conflicted with the FOREIGN KEY constraint ... I know this can be solved by creating a relation in the LINQ diagram between Events and groups. And then setting the entity itself. But i don't want to load the events everytime i ask a list of groups. All i need is some way that when inserting the group fails, the event insert won't be comitted in the database. Sorry if this is a bit unclear, My english isn't really good. Thanks in advance!

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• SSL certificates: No Client certificate key exhange

  - by user334246

  I am trying to access a WCF web service, that is using two way SSL encryption. When I try to call the service I get a System.ServiceModel.Security.SecurityNegotiationException: Could not establish secure channel for SSL/TLS with authority 'XXX.xx'. --- System.Net.WebException: The request was aborted: Could not create SSL/TLS secure channel. I have tried activating wire shark, to see what is sent to and from the server: I see a client hello and a server hello. But there is no client response to the server hello. I was expecting a "Certificate. Client key exchange. Change cipher. Encrypted handshake Message" package, but none is sent. I'm thinking it is a problem with the certificate sent by the server, that somehow my client server does not trusy it. Here is what I have already tried: I have created the certificate, through the proper authority, though I could have made a mistake in the certificate request without knowing it. I have added the two root certificates to: trusted root certificates, trusted publishers and trusted people. I have also added the client certificate to trusted people. My colleague has succeded in establishing connection on a win 2008 server (i'm using a 2003, because it is necessary for some odd reason - don't ask). I can't see any differences in our approach, so i'm a bit lost. Any help would be greatly appreciated.

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• Using NSURLRequest to pass key-value pairs to PHP script with POST

  - by Ralf Mclaren

  Hi, I'm fairly new to objective-c, and am looking to pass a number of key-value pairs to a PHP script using POST. I'm using the following code but the data just doesn't seem to be getting posted through. I tried sending stuff through using NSData as well, but neither seem to be working. NSDictionary* data = [NSDictionary dictionaryWithObjectsAndKeys: @"bob", @"sender", @"aaron", @"rcpt", @"hi there", @"message", nil]; NSURL *url = [NSURL URLWithString:@"http://myserver.com/script.php"]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; [request setHTTPMethod:@"POST"]; [request setHTTPBody:[NSData dataWithBytes:data length:[data count]]]; NSURLResponse *response; NSError *err; NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err]; NSLog(@"responseData: %@", content); This is getting sent to this simple script to perform a db insert: <?php $sender = $_POST['sender']; $rcpt = $_POST['rcpt']; $message = $_POST['message']; //script variables include ("vars.php"); $con = mysql_connect($host, $user, $pass); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("mydb", $con); mysql_query("INSERT INTO php_test (SENDER, RCPT, MESSAGE) VALUES ($sender, $rcpt, $message)"); echo "complete" ?> Any ideas?

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• Understanding Flash SWC's imported into Flex Builder 3 and key framed animation

  - by Hank Scorpio

  I am trying to understand what is going on in a SWC that I am importing from Flash CS4 into Flex Builder 3. Specifically I am using a SWC supplied by a Designer as the animation for a custom preloader (a subclassed DownloadProgressBar). The issue I am trying to understand is, once the FlexEvent.INIT_COMPLETE is fired, I cleanup by removing the swc by running this : removeChild(myPreloader); myPreloader = null; though even after I have removed this (which is successful, as I have checked by comparing this.numChildren before and after the call) the key framed animation still continues to run (not visibly). This has been detected by the Designer placing a trace in the time line of the animation (in Flash). Can anyone tell me why is it, that even after I have removed the animation from the subclassed DownloadProgressBar, it still keeps running ? Also, is it standard practice when importing SWCs to manage the cleanup of resources from the Flash side of things (much like releasing memory in obj-c). I find it counter intuitive that removing the child from the Flex side does not stop the animation. Any clues to this would be greatly appreciated.

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• Sockets server design advice

  - by Rob

  We are writing a socket server in c# and need some advice on the design. Background: Clients (from mobile devices) connect to our server app and we leave their socket open so we can send data back down to them whenever we need to. The amount of data varies but we generally send/receive data from each client every few seconds, so it's quite intensive. The amount of simultaneous connections can range from 50-500 (and more in the future). We have already written a server app using async sockets and it works, however we've come across some stumbling blocks and we need to make sure that what we're doing is correct. We have a collection which holds our client states (we have no socket/connection pool at the moment, should we?). Each time a client connects we create a socket and then wait for them to send us some data and in receiveCallBack we add their clientstate object to our connections dictionary (once we have verified who they are). When a client object then signs off we shutdown their socket and then close it as well as remove them from our collection of clients dictionary. Presumably everything happens in the right order, everything works as expected. However, almost everyday it stops accepting connections, or so we think, either that or it connects but doesn't actually do anything past that and we can't work out why it's just stopping. There are few things that we'r'e unsure about 1) Should we be creating some kind of connection pool as opposed to just a dictionary of client sockets 2) What happens to the sockets that connect but then don't get added to our dictionary, they just linger around in memory doing nothing, should we create ANOTHER dictionary that holds the sockets as soon as they are created? 3) What's the best way of finding if clients are no longer connected? We've read some many methods but we're not sure of the best one to use, send data or read data, if so how? 4) If we loop through the connections dictonary to check for disposed clients, should we be locking the dictionary, if so how does this affect other clients objects trying to use it at the same time, will it throw an error or just wait? 5) We often get disposedSocketException within ReceiveCallBack method at random times, does this mean we are safe to remove that socket from the collection? We can't seem to find any production type examples which show any of this working. Any advice would be greatly received

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• Composite key syntax in Boost MultiIndex

  - by Sarah

  Even after studying the examples, I'm having trouble figuring out how to extract ranges using a composite key on a MultiIndex container. typedef multi_index_container< boost::shared_ptr< Host >, indexed_by< hashed_unique< const_mem_fun<Host,int,&Host::getID> >, // ID index ordered_non_unique< const_mem_fun<Host,int,&Host::getAgeInY> >, // Age index ordered_non_unique< const_mem_fun<Host,int,&Host::getHousehold> >, // Household index ordered_non_unique< // Age & eligibility status index composite_key< Host, const_mem_fun<Host,int,&Host::getAgeInY>, const_mem_fun<Host,bool,&Host::isPaired> > > > // end indexed_by > HostContainer; My goal is to get an iterator pointing to the first of the subset of elements in HostContainer hmap that has age partnerAge and returns false to Host::isPaired(): std::pair< hmap::iterator,hmap::iterator > pit = hmap.equal_range(boost::make_tuple( partnerAge, false ) ); I think this is very wrong. How/Where do I specify the iterator index (which should be 3 for age & eligibility)? I will include other composite keys in the future. What exactly are the two iterators in std::pair? (I'm copying syntax from an example that I don't understand.) I would ideally use std::count to calculate the number of elements of age partnerAge that are eligible (return false to Host::isPaired()). What is the syntax for extracting the sorted index that meets these requirements? I'm obviously still learning C++ syntax. Thanks in advance for any help.

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• How to change the primary key to be non-clustered?

  - by AngryHacker

  Part-time reluctant DBA here. I want to change an existing primary key index from clustered to non-clustered. And the syntax is escaping me. This is how it's scripted out right now. ALTER TABLE [dbo].[Config] WITH NOCHECK ADD CONSTRAINT [PK_Config] PRIMARY KEY CLUSTERED ( [ConfigID] ) ON [PRIMARY] I am not seeing an ALTER CONSTRAINT statement in the online docs.

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• Google Maps Api android key

  - by Cookie

  Hi, I have some trouble testing my Android application which includes the google maps API. The ooficial API example worked just fine but if I copy the code into my own project it keeps saying: "The application has stopped unexpectedly". I looked up the key in the keystore several times and registered it with google. Even tried reinstalling the SDK. Does anybody know what the problem is? Thanks in advance 05-16 14:31:11.142: ERROR/ActivityThread(662): Failed to find provider info for com.google.settings 05-16 14:31:11.150: ERROR/ActivityThread(662): Failed to find provider info for com.google.settings 05-16 14:31:12.598: ERROR/MediaPlayerService(542): Couldn't open fd for content://settings/system/notification_sound 05-16 14:31:12.624: ERROR/MediaPlayer(562): Unable to to create media player 05-16 14:31:05.098: ERROR/ActivityThread(608): Failed to find provider info for android.server.checkin 05-16 14:31:06.538: ERROR/ActivityThread(608): Failed to find provider info for android.server.checkin 05-16 14:31:06.645: ERROR/ActivityThread(608): Failed to find provider info for android.server.checkin 05-16 14:31:12.803: ERROR/AndroidRuntime(715): ERROR: thread attach failed 05-16 14:31:13.698: ERROR/ActivityThread(723): Failed to find provider info for com.google.settings 05-16 14:31:13.987: ERROR/AndroidRuntime(723): Uncaught handler: thread main exiting due to uncaught exception PS: there are some exceptions following but none pointing to my code, everything in background processes.

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• Design-time failure: WPF, Usercontrols and Namespaces

  - by Simon Woods

  Hi I have a very simple WPF project comprising a Window and Usercontrol. I'm very much in a learning phase. It works fine when I run it. However, I am unable to see the form in design time. The problem, I believe is something to do with namespaces, but I don't understand where. It may well be a simple error Main Window XML <Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:views="clr-namespace:UserLogin" x:Class="UserLogin.MainView" x:Name="MainViewWindow" mc:Ignorable="d" Title="Login" Height="141" Width="347" > <Grid> <views:LoginView /> </Grid> </Window> Main Window CodeBehind Imports Microsoft.VisualBasic Imports System Imports System.Windows Imports UserLogin Namespace UserLogin Partial Public Class MainView Inherits System.Windows.Window Public Sub New() InitializeComponent() End Sub End Class End Namespace Usercontrol XAML <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" x:Class="UserLogin.LoginView" x:Name="LoginViewControl" mc:Ignorable="d" d:DesignHeight="96" d:DesignWidth="298"> <Grid Height="96" Width="298"> <Button Command="{Binding OKCommand}" Height="21" Margin="0,0,90,16" Name="btnOK" VerticalAlignment="Bottom" HorizontalAlignment="Right" Width="76">OK</Button> <Button Command="{Binding CancelCommand}" Height="21" HorizontalAlignment="Right" Margin="0,0,9,16" Name="btnCancel" VerticalAlignment="Bottom" Width="75">Cancel</Button> <Label Height="23" HorizontalAlignment="Left" Margin="10,5,0,0" Name="Label1" VerticalAlignment="Top" Width="85">Name:</Label> <Label HorizontalAlignment="Left" Margin="10,32,0,0" Name="Label2" Width="85" Height="29" VerticalAlignment="Top">Password:</Label> <TextBox Margin="0,31,6,0" Name="txtPassword" Height="22" VerticalAlignment="Top" HorizontalAlignment="Right" Width="182" /> <ComboBox Height="22" Margin="110,6,6,0" Name="cboNames" VerticalAlignment="Top" /> </Grid> </UserControl> Usercontrol CodeBehind Imports Microsoft.VisualBasic Imports System Imports UserLogin Namespace UserLogin Partial Public Class LoginView Inherits System.Windows.Controls.UserControl Public Sub New() InitializeComponent() End Sub End Class End Namespace I think I'm missing something this namespace xmlns:views="clr-namespace:UserLogin" since intellisense doesn't give me the usercontrol declared within it in the XAML designer but rather reports the error "Unable to load the metadata for the assembly ... etc etc" Thx for any suggestions Simon

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• "The given key was not present in the dictionary" ASP.NET error on IIS7

  - by eugeneK

  Hi, i have this error on one of my sites. Searched thought all project found no Dictionary of some kind. Read somewhere it could be caused by Url Rewrite module on IIS 7 which i'm using for certain redirects. Error appears on all pages thought the site, 99% sure only on pages that use Url Rewriting This is error's stack at System.ThrowHelper.ThrowKeyNotFoundException() at System.Collections.Generic.Dictionary`2.get_Item(TKey key) at System.Data.DataView.System.Collections.IList.get_Item(Int32 recordIndex) at System.Web.UI.WebControls.ListViewPagedDataSource.EnumeratorOnIList.get_Current() at System.Web.UI.WebControls.ListView.CreateItemsWithoutGroups(ListViewPagedDataSource dataSource, Boolean dataBinding, InsertItemPosition insertPosition, ArrayList keyArray) at System.Web.UI.WebControls.ListView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) at System.Web.UI.WebControls.ListView.PerformDataBinding(IEnumerable data) at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) at System.Web.UI.WebControls.DataBoundControl.PerformSelect() at System.Web.UI.WebControls.ListView.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() at System.Web.UI.WebControls.ListView.CreateChildControls() at System.Web.UI.Control.EnsureChildControls() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)HTTP_CONNECTION:Keep-Alive HTTP_ACCEPT:image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-icq, / HTTP_ACCEPT_LANGUAGE:en HTTP_COOKIE:__utma=248870149.1673016949.1252234176.1276449788.1276595165.49; __utmz=248870149.1276595165.49.55.utmcsr=search|utmccn=(organic)|utmcmd=organic|utmctr=???%20??; wooTracker=C1T8MWMAZWQVHJXWROHB25SO4S0B7UO0; __utmb=248870149.6.10.1276595165; __utmc=248870149; wooTracker=C1T8MWMAZWQVHJXWROHB25SO4S0B7UO0; machine-id=87.69.44.154%3A1253914747956; wooMeta=ODAwMzkmMSYxJjc1MDE5JjEyNTUyMTQwODEwMjkmMTI1NTIxNDE1NjA0OCYmMTAwJiYzMDAyODQmJiYm; _csoot=1267959625296; _csuid=X4c1ef311c39a67; ASP.NET_SessionId=zzdn5b45uqyhw145ptqhxe20 HTTP_HOST:**** HTTP_REFERER:***** HTTP_USER_AGENT:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6) HTTP_X_CEPT_ENCODING:gzip, deflate ***** Is anyone familiar with fix or at least where to look for one ?

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• Nhibernate/Hibernate, lookup tables and object design

  - by Simon G

  Hi, I've got two tables. Invoice with columns CustomerID, InvoiceDate, Value, InvoiceTypeID (CustomerID and InvoiceDate make up a composite key) and InvoiceType with InvoiceTypeID and InvoiceTypeName columns. I know I can create my objects like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceType InvoiceType { get; set; } } public class InvoiceType { public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } So the generated sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice WHERE CustomerID = x AND InvoiceDate = y SELECT InvoiceTypeID, InvoiceTypeName FROM InvoiceType WHERE InvoiceTypeID = z But rather that having two select queries executed to retrieve the data I would rather have one. I would also like to avoid using child object for simple lookup lists. So my object would look something like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } And my sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice INNER JOIN InvoiceType ON Invoice.InvoiceTypeID = InvoiceType.InvoiceTypeID WHERE CustomerID = x AND InvoiceDate = y My question is how do I create the mapping for this? I've tried using join but this tried to join using CustomerID and InvoiceDate, am I missing something obvious? Thanks

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• Entity Framework - Foreign key constraints not added for inherited entity

  - by Tri Q

  Hello, It appears to me that a strange phenomenon is occurring with inherited entities (TPT) in EF4. I have three entities. 1. Asset 2. Property 3. Activity Property is a derived-type of Asset. Property has many activities (many-to-many) When modeling this in my EDMX, everything seems fine until I try to insert a new Property into the database. If the property does not contain any Activity, it works, but all hell breaks loose when I add some new activities to the new Property. As it turns out after 2 days of crawling the web and fiddling around, I noticed that in the EF store (SSDL) some of the constraints between entities were not picked up during the update process. Property_Activity table which links properties and activities show only one constraint FK_Property_Activity_Activity but FK_Property_Activity_Property was missing. I knew this is an Entity Framework anomoly because when I switched the relationship in the database to: Asset <-- Asset_Activity <-- Activity After an update, all foreign key constraints are picked up and the save is successful, with or without activities in the new property. Is this intended or a bug in EF? How do I get around this problem? Should I abandon inheritance altogether?

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• Linked List Design

  - by Jim Scott

  The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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• Integer Surrogate Key?

  - by CitadelCSAlum

  I need something real simple, that for some reason I am unable to accomplish to this point. I have also been unable to Google the answer surprisingly. I need to number the entries in different tables uniquely. I am aware of AUTO INCREMENT in MySQL and that it will be involved. My situation would be as follows If I had a table like Table EXAMPLE ID - INTEGER FIRST_NAME - VARCHAR(45) LAST_NAME - VARCHAR(45) PHONE - VARCHAR(45) CITY - VARCHAR(45) STATE - VARCHAR(45) ZIP - VARCHAR(45) This would be the setup for the table where ID is an integer that is auto-incremented every time an entry is inserted into the table. The thing I need is that I do not want to have to account for this field when inserting data into the database. From my understanding this would be a surrogate key, that I can tell the database to automatically increment and I do not have to include it in the INSERT STATEMENT so instead of INSERT INTO EXAMPLE VALUES (2,'JOHN','SMITH',333-333-3333,'NORTH POLE'.... I can leave out the first ID column and just write something like INSERT INTO EXAMPLE VALUES ('JOHN','SMITH'.....etc) Notice I Wouldnt have to define the ID column... I know this is a very common task to do, but for some reason I cant get to the bottom of it. I am using MySQL, just to clarify. Thanks alot

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