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• Relational algebra help?!

  - by Tom

  im new to relational algebra and finding it difficult. Ive answered a few questions, however they where relatively simple. Could do with help with these though. Database Patient (PatientCode, PatientSurname, PatientFirstname, PatientSex, PatientAge, PatientOccupation, PatientHeight, PatientWeight, PatientAddress) Doctor (DoctorCode, DoctorSurName, DoctorFirstName, DoctorPrivateAddress, MobileNo, Doctor Specilisim) Operation (Operation Code, PatientCode, DoctorCode, Date, Time, Result, OperationType) Is_Seen_By (PatientCode, DoctorCode, Date, Time). Q1. Find the surname and gender of the patients that have been operated on by doctor "DR333" and results have not been successful. Q2. Find the code of the operations that have been done on the 18th of November 2010 and have been successful, please also list the name of the doctors which were involved with the operation.

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• Need a .NET Dictionary<string,object> with just a little more functionality.

  - by Ronnie Overby

  I need a dictionary but I also need to store a boolean value about the object in the dictionary. What's the best way for this. Something like Dictonary<string,object,bool> would be ideal, but doesn't exist. My first idea was: public class SomeObject { public object Value { get; set; } public bool Flag { get; set; } } // and then use: Dictionary<string,SomeObject> myDictionary; My 2nd idea was to implement IDictionary and contain two dictionaries within that were manipulated by the implemented methods and property accessors. My 3rd idea was to see what the folks at StackOverflow would do.

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• object assignment

  - by sandhya

  Hi i have a scenario like myclass obj1 = new myclass(); ............//some operations on obj1; myclass obj2 = new myclass(); obj2 = obj1; now, my problem is if i modify any parameter, it is effected in both objects (as both refer to same location). but, when i modify obj2 parameter, it should not parameter value in obj1. (means both should not point to same location). how can i do that? please help me

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• Generate non-identity primary key

  - by MikeWyatt

  My workplace doesn't use identity columns or GUIDs for primary keys. Instead, we retrieve "next IDs" from a table as needed, and increment the value for each insert. Unfortunatly for me, LINQ-TO-SQL appears to be optimized around using identity columns. So I need to query and update the "NextId" table whenever I perform an insert. For simplicity, I do this immediately creating the new object. Since all operations between creation of the data context and the call to SubmitChanges are part of one transaction, do I need to create a separate data context for retrieving next IDs? Each time I need an ID, I need to query and update a table inside a transaction to prevent multiple apps from grabbing the same value. Is a separate data context the only way, or is there something better I could try?

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• How do I combine these similar linq queries into one?

  - by MikeD

  This is probably a basic LINQ question. I have need to select one object and if it is null select another. I'm using linq to objects in the following way, that I know can be done quicker, better, cleaner... public Attrib DetermineAttribution(Data data) { var one = from c in data.actions where c.actionType == Action.ActionTypeOne select new Attrib { id = c.id, name = c.name }; if( one.Count() > 0) return one.First(); var two = from c in data.actions where c.actionType == Action.ActionTypeTwo select new Attrib { id = c.id, name = c.name }; if (two.Count() > 0 ) return two.First(); } The two linq operations differ only on the where clause and I know there is a way to combine them. Any thoughts would be appreciated.

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• SQLite doesn't have booleans or date-times...but C# does

  - by DanM

  I've been thinking about using SQLite for my next project, but I'm concerned that it seems to lack proper datetime and bit data types. If I use DbLinq (or some other ORM) to generate C# classes, will the data types of the properties be "dumbed down"? Will date-time data be placed in properties of type string or double? Will boolean data be placed in properties of type int? If yes, what are the implications? I'm envisioning a scenario where I need to write a whole second layer of classes with more specific data types and do a bunch of transformations and casts, but maybe it's not so bad. If you have any experience with this or a similar scenario, what are your "lessons learned"?

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• multiple occurences of HandleCreated for a single control

  - by Asher

  I’m using control that needs to be register to asynchronous events. The events will be raised in the UI thread using the ISynchronizeInvoke interface implemented by WinForms controls I can’t register to the event at the constructor because it will allow calling the event handler before the control is fully created. during which calls to ISynchronizeInvoke are not allowed. Solution to that problem is to use the perform the asynchronous event registration from an event handler to the HandleCreated instead of registering from the constructor. however, this poses another issue, in some scenations the HandleCreated event is raised multiple times as result of change at the control state. For example, each changing of the “RightToLeft” property causes a WMCreate message that cause raising the “HandleCreated” event. How can I prevent the multiply times of event rising? Is there is another way to know when the control is created and display for the first time? I can keep a boolean flag in the HandleCreated, however it feels like a hack and I am wondering if there is a better way to handle this issue.

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• How to leverage Spring Integration in a real-world JMS distributed architecture?

  - by ngeek

  For the following scenario I am looking for your advices and tips on best practices: In a distributed (mainly Java-based) system with: many (different) client applications (web-app, command-line tools, REST API) a central JMS message broker (currently in favor of using ActiveMQ) multiple stand-alone processing nodes (running on multiple remote machines, computing expensive operations of different types as specified by the JMS message payload) How would one best apply the JMS support provided by the Spring Integration framework to decouple the clients from the worker nodes? When reading through the reference documentation and some very first experiments it looks like the configuration of an JMS inbound adapter inherently require to use a subscriber, which in a decoupled scenario does not exist. Small side note: communication should happen via JMS text messages (using a JSON data structure for future extensibility).

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• F# return type coercion

  - by Alex

  Hi, In F# I have a function that returns System.Linq.Expression instances: and System.Object with member this.ToExpression() = match this with | :? System.Int32 -> Expression.Constant(this) :> Expression | :? System.Boolean -> Expression.Constant(this) :> Expression | :? Tml.Runtime.Seq as s -> s.ToExpression() | _ -> failwith "bad expression" If I omit the type coercions on the return values F# will infer the return type of the function to ConstantExpression. My first thought was to explicitly mark the return type as being : #Expression, but that didn't work. Is there a more elegant way of doing this that doesn't involve manually casting return types to the most generic type? Thanks.

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• Android: How to find the position clicked from the context menu

  - by Josemalive

  Hi, I have a list view filled with data. I set up a context menu for the listview using the following code: list.setOnCreateContextMenuListener ( new View.OnCreateContextMenuListener() { public void onCreateContextMenu(ContextMenu menu, View view, ContextMenu.ContextMenuInfo menuInfo) { AdapterContextMenuInfo mi =(AdapterContextMenuInfo) menuInfo; menu.add(0, 0, 0, "Delete item"); } } ); I have the following method override to control de contextmenu menuitem selected: @Override public boolean onContextItemSelected(MenuItem item) { switch(item.getItemId()) { case 0: ShowAlert("hello from delete item"); break; default: return super.onContextItemSelected(item); } return true; } In this overrided method, how could i find the item of the list view that was clicked? Thanks in advance. Best Regards. Jose

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• PHP Comparing 2 Arrays For Existence of Value in Each

  - by Dr. DOT

  I have 2 arrays. I simply want to know if one of the values in array 1 is present in array 2. Nothing more than returning a boolean true or false Example A: $a = array('able','baker','charlie'); $b = array('zebra','yeti','xantis'); Expected result = false Example B: $a = array('able','baker','charlie'); $b = array('zebra','yeti','able','xantis'); Expected result = true So, would it be best to use array_diff() or array_search() or some other simple PHP function? Thanks!

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• ShellExecute not working from IDE but works otherwise.

  - by Altar

  I want to create and then open a txt file using the ShellExecute command. I have used this code for years with Delphi 7 and it worked: function Executa(CONST ExeName, Parameters: string): Boolean; begin if Parameters= '' then Result:= ShellExecute(0, 'open', PChar(ExeName), NIL , nil, SW_SHOWNORMAL)> 32 else Result:= ShellExecute(0, 'open', PChar(ExeName), PChar(Parameters), nil, SW_SHOWNORMAL)> 32; end; Now, I switch to Windows 7 (don't like it; they stuck it on my throat with my new laptop) 64 bit and the code is not working anymore when it runs from IDE. Delhi shows the CPU window with the caption "CPU-Process unknown (2352)". I close the CU windows and everything works fine until I close the application, when Delphi shows the CPU window one more time. If I run the app from outside IDE, it works fine. Looks like the debugger has something to say to me, but I don't know what.

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• Upsert - Efficient Update or Insert in VB.Net, SQL Server

  - by HK1

  I'm trying to understand how to streamline the process of inserting a record if none exists or updating a record if it already exists. I'm not using stored procedures, although maybe that would be the most efficient way of doing this. The actual scenario in which this is necessary is saving a user preference/setting to my SettingsUser table. In MS Access I would typically pull a DAO recordset looking for the specified setting. If the recordset comes back empty then I know I need to add a new record which I can do with the same recordset object. On the other hand, if it isn't empty, I can just update the setting's value right away. In theory, this is only two database operations. What is the recommended way of doing this in .NET?

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• Java IO (javase 6)- Help me understand the effects of my sample use of Streams and Writers...

  - by Daddy Warbox

  BufferedWriter out = new BufferedWriter( new OutputStreamWriter( new BufferedOutputStream( new FileOutputStream("out.txt") ) ) ); So let me see if I understand this: A byte output stream is opened for file "out.txt". It is then fed to a buffered output stream to make file operations faster. The buffered stream is fed to an output stream writer to bridge from bytes to characters. Finally, this writer is fed to a buffered writer... which adds another layer of buffering? Hmm...

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• Expression Tree : C#

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally when our LINQ to SQL query compiler translates it to parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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• WPF - Pausing the UI Thread?

  - by Rachel

  I have a tab control with draggable tabs. When the mouse is released it removes the selected tab from the tabControl and adds it to its new location. My problem is that the TabControl draws itself after removing the tab, and then again when adding the tab so there is a very noticeable flicker that shows the tab behind the tab being moved. Is there a way I can pause the UI thread so the tab control does not redraw until both the Remove and the Insert operations finish? Or perhaps some other alternative way of rearranging the tab items? The Drag/Drop operation exists in a separate code file as an Attached Property

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• How sophisticated should be DAL?

  - by Andrew Florko

  Basically, DAL (Data Access Layer) should provide simple CRUD (Create/Read/Update/Delete) methods but I always have a temptation to create more sophisticated methods in order to minimize database access roundtrips from Business Logic Layer. What do you think about following extensions to CRUD (most of them are OK I suppose): Read: GetById, GetByName, GetPaged, GetByFilter... e.t.c. methods Create: GetOrCreate methods (model entity is returned from DB or created if not found and returned), Create(lots-of-relations) instead of Create and multiple AssignTo methods calls Update: Merge methods (entities list are updated, created and deleted in one call) Delete: Delete(bool children) - optional children delete, Cleanup methods Where do you usually implement Entity Cache capabilities? DAL or BLL? (My choice is BLL, but I have seen DAL implementations also) Where is the boundary when you decide: this operation is too specific so I should implement it in Business Logic Layer as DAL multiple calls? I often found insufficient BLL operations that were implemented in dozen database roundtrips because developer was afraid to create a bit more sophisticated DAL. Thank you in advance!

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• Findbugs warning: Equals method should not assume anything about the type of its argument

  - by Uri

  When running FindBugs on my project, I got a few instances of the error described above. Namely, my overriding versions of equals cast the RHS object into the same type as the object in which the overriding version is defined. However, I'm not sure whether a better design is possible, since AFAIK Java does not allow variance in method parameters, so it is not possible to define any other type for the equals parameter. Am I doing something very wrong, or is FindBugs too eager? A different way to phrase this question is: what is the correct behavior if the object passed to equals is not the same type as an LHS: Is this a false, or should there be an exception? For example: public boolean equals(Object rhs) { MyType rhsMyType = (MyType)rhs; // Should throw exception if(this.field1().equals(rhsMyType.field1())... // Or whatever }

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• How to organize code using an optional assembly reference?

  - by apoorv020

  I am working on a project and want to optionally use an assembly if available. This assembly is only available on WS 2008 R2, and my ideal product whould be a common binary for both computers with and without the assembly. However, I'm primarily developing on a Windows 7 machine, where I cannot install the assembly. How can I organize my code so that I can (with minimum changes) build my code on a machine without the assembly and secondly, how do I ensure that I call the assembly functions only when it is present. (NOTE : The only use of the optional assembly is to instantiate a class in the library and repeatedly call a (single) function of the class, which returns a boolean. The assembly is fsrmlib, which exposes advanced file system management operations on WS08R2.) I'm currently thinking of writing a wrapper class, which will always return true if the assembly is not present. Is this the right way to go about doing this?

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• Authenticating wcf service

  - by Muhammad Jamal Shaikh

  hi , i want to implement a web service which is both in java and .net.but i will first create a wcf service and later convert the code to java . for securing the webservice , i have this in my mind. i shall be implementing asp.net form authentication type of stuff . i intent to sent a token to the client on providing valid userID and password to the login method. in return i would send a token. on all other service operations i shall check the token . Now i have a wcf client and a wcf service . what should be the shortest way forward ?should i use soap auth header to send the user ID and password and how should the token be transported ( in which field ? http or soap's ?) . P.S: of course i shall enable ssl later.

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• Is there any sense in performing binary AND with a number where all bits are set to 1

  - by n535

  Greetings everybody. I have seen examples of such operations for so many times that I begin to think that I am getting something wrong with binary arithmetic. Is there any sense to perform the following: byte value = someAnotherByteValue & 0xFF; I don't really understand this, because it does not change anything anyway. Thanks for help. P.S. I was trying to search for information both elsewhere and here, but unsuccessfully. EDIT: Well, off course i assume that someAnotherByteValue is 8 bits long, the problem is that i don't get why so many people ( i mean professionals ) use such things in their code. For example in Jon Skeet's MiscUtil there is: uint s1 = (uint)(initial & 0xffff); where initial is int.

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• Want procmail to run a custom python script, everytime a new mail shows up

  - by Maddy

  I have a pretty usual requirement with procmail but I am unable to get the results somehow. I have procmailrc file with this content: :0 * ^To.*@myhost | /usr/bin/python /work/scripts/privilege_emails_forward.py Wherein my custom python script(privilege_emails_forward.py) will be scanning through the email currently received and do some operations on the mail content. But I am unable to get the script getting executed at the first shot(let alone scanning through the mail content). Is this a correct way of invoking an external program(python) as soon as new mail arrives? And how does my python program(privilege_emails_forward.py) will receive the mail as input? I mean as sys.argv or stdin????

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• Call an IOUSBDeviceInterface function on an obj-c object instead of a C structure

  - by b1onic

  Let's say I want to close an USB device. Here is a C structure representing the USB device: struct __USBDevice { uint16_t idProduct; io_service_t usbService; IOUSBDeviceInterface **deviceHandle; IOUSBInterfaceInterface **interfaceHandle; Boolean open; }; typedef struct __USBDevice *USBDeviceRef; Here is the code to close the device: // device is a USBDeviceRef structure // USBDeviceClose is a function member of IOUSBDeviceInterface C Pseudoclass (*device->deviceHandle)->USBDeviceClose(device->deviceHandle); Now imagine that the device properties are declared in an obj-c class @interface Device : NSObject { NSNumber idProduct io_service_t usbService; IOUSBDeviceInterface **deviceHandle; IOUSBInterfaceInterface **interfaceHandle; BOOL open; } @end How would I do to call USBDeviceClose() ?

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• 'e-Commerce' scalable database model

  - by Ruben Trancoso

  I would like to understand database scalability so I've just heard a talk about Habits of Highly Scalable Web Applications http://techportal.ibuildings.com/2010/03/02/habits-of-highly-scalable-web-applications/ On it, the presenter mainly talk about relational database scalability. I also have read something about MapReduce and Column oriented tables, big tables, hypertable etc... trying to understand which are the most up to date methods to scale web application data. But the second group, to me, is being hard to understand where it fits. It serves as transactional, reliable data store? or not, its just for large access and processing and to handle fine graned operations we will ever need to rely on RDBMSs? Could someone give a comprehensive landscape for those new technologies and how to use it?

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• Generic WithEvents

  - by serhio

  Error: 'WithEvents' variables can only be typed as classes, interfaces or type parameters with class constraints Background: Public Class Tadpole(Of T As IVisibleChanged, P As IVisibleChanged) Private WithEvents _Tad As T ' ERROR ' Private WithEvents _Pole As P ' ERROR ' Public Property Tad() As T ... Public Property Pole() As P ... End Class ''' IVisibleChanged ''' Public Interface IVisibleChanged Property Visible() As Boolean Event VisibleChanged As EventHandler End Interface Workaround: a. Use AddHandler to handle events defined in a structure. EDIT b. use Private WithEvents _Tad AsIVisibleChanged (M.A. Hanin) c. ?

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