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  • How does multiple implementing multiple COM interfaces work in C++?

    - by Martin
    I am trying to understand this example code regarding Browser Helper Objects. Inside, the author implements a single class which exposes multiple interfaces (IObjectWithSite, IDispatch). His QueryInterface function performs the following: if(riid == IID_IUnknown) *ppv = static_cast<BHO*>(this); else if(riid == IID_IObjectWithSite) *ppv = static_cast<IObjectWithSite*>(this); else if (riid == IID_IDispatch) *ppv = static_cast<IDispatch*>(this); I have learned that from a C perspective, interface pointers are just pointers to VTables. So I take it to mean that C++ is capable of returning the VTable of any implemented interface using static_cast. Does this mean that a class constructed in this way has a bunch of VTables in memory (IObjectWithSite, IDispatch, etc)? What does C++ do with the name collisions on the different interfaces (they each have a QueryInterface, AddRef and Release function), can I implement different methods for each of these?

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  • ASP.NET MVC 3 embrace dynamic type - CSDN.NET - CSDN Software Development Channel

    - by user559071
    About a decade ago, Microsoft will all bet on the WebForms and static types. With the complete package from scattered to the continuous development, and now almost every page can be viewed as its own procedure. Subsequent years, the industry continued to move in another direction, love is better than separation package, better than the late binding early binding to the idea. This leads to two very interesting questions. The first is the problem of terminology. Consider the original Smalltalk MVC model, view and controller is not only tightly coupled together, and usually in pairs. Most of the framework is that Microsoft, including the classic VB, WinForms, WebForms, WPF and Silverlight, they both use the code behind file to store the controller logic. But said "MVC" usually refers to the view and controller are loosely coupled framework. This is especially true for the Web framework, HTML form submission mechanism allows any views submitted to any of the controller. Since this article was mainly talking about Web technologies, so we need to use the modern definition. The second question is "If you're Microsoft, how to change orbit without causing too much pressure to the developer?" So far, the answer is: new releases each year, until the developers meet up. ASP.NET MVC's first product was released last March. Released in March this year, ASP.NET MVC 2.0. 3.0 RC 2 is currently in phase, expected to be released next March. December 10, Microsoft released ASP.NET MVC 3.0 Release Candidate 2. RC 2 is built on top of Microsoft's commitment to the jQuery: The default project template into jQuery 1.4.4, jQuery Validation 1.7 and jQuery UI. Although people think that Microsoft will focus shifted away from server-side controls to be a joke, but the introduction of Microsoft's jQuery UI is that this is the real thing. For those worried about the scalability of the developers, there are many excellent control can replace the session state. With SessionState property, you can tell the controller session state is read-only, read-write, or can be completely ignored in the. This site is no single server, but if a server needs to access another server session state, then this approach can provide a great help. MVC 3 contains Razor view engine. By default, the engine will be encoded HTML output, so that we can easily output on the screen the text of the original. HTML injection attacks even without the risk of encoded text can not easily prevent the page rendering. For many C # developers in the end do what is most shocking that MVC 3 for the controller and view and embrace the dynamic type. ViewBag property will open a dynamic object, developers can run on top of the object to add attributes. In general, it is used to send the view from the controller non-mode data. Scott Guthrie provides state of the sample contains text (such as the current time) and used to assemble the list box entries. Asked Link: http://www.infoq.com/cn/news/2010/12/ASPNET-MVC-3-RC-2; jsessionid = 3561C3B7957F1FB97848950809AD9483

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  • Force external function to be const

    - by vanna
    Here is my problem. I made a class with a member function declared as const that uses an external function that I cannot modify (declared in someone else's code) and that is not declared const. More precisely Someone else's code class B { public: void foo(); }; My code class A : public B { public: void bar() const { this->foo(); } }; I know that for member data we can force const-correctness by using mutable or const_cast. How can I 'hack' foo such that my compiler understands that I would like to use it as if it was const even if it is not declared in someone else's code ?

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  • Make interchangeable class types via pointer casting only, without having to allocate any new objects?

    - by HostileFork
    UPDATE: I do appreciate "don't want that, want this instead" suggestions. They are useful, especially when provided in context of the motivating scenario. Still...regardless of goodness/badness, I've become curious to find a hard-and-fast "yes that can be done legally in C++11" vs "no it is not possible to do something like that". I want to "alias" an object pointer as another type, for the sole purpose of adding some helper methods. The alias cannot add data members to the underlying class (in fact, the more I can prevent that from happening the better!) All aliases are equally applicable to any object of this type...it's just helpful if the type system can hint which alias is likely the most appropriate. There should be no information about any specific alias that is ever encoded in the underlying object. Hence, I feel like you should be able to "cheat" the type system and just let it be an annotation...checked at compile time, but ultimately irrelevant to the runtime casting. Something along these lines: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Under the hood, the factory method is actually making a NodeBase class, and then using a similar reinterpret_cast to return it as a Node<AccessorFoo>*. The easy way to avoid this is to make these lightweight classes that wrap nodes and are passed around by value. Thus you don't need casting, just Accessor classes that take the node handle to wrap in their constructor: AccessorFoo foo (NodeBase::createViaFactory()); AccessorBar bar (foo.getNode()); But if I don't have to pay for all that, I don't want to. That would involve--for instance--making a special accessor type for each sort of wrapped pointer (AccessorFooShared, AccessorFooUnique, AccessorFooWeak, etc.) Having these typed pointers being aliased for one single pointer-based object identity is preferable, and provides a nice orthogonality. So back to that original question: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Seems like there would be some way to do this that might be ugly but not "break the rules". According to ISO14882:2011(e) 5.2.10-7: An object pointer can be explicitly converted to an object pointer of a different type.70 When a prvalue v of type "pointer to T1" is converted to the type "pointer to cv T2", the result is static_cast(static_cast(v)) if both T1 and T2 are standard-layout types (3.9) and the alignment requirements of T2 are no stricter than those of T1, or if either type is void. Converting a prvalue of type "pointer to T1" to the type "pointer to T2" (where T1 and T2 are object types and where the alignment requirements of T2 are no stricter than those of T1) and back to its original type yields the original pointer value. The result of any other such pointer conversion is unspecified. Drilling into the definition of a "standard-layout class", we find: has no non-static data members of type non-standard-layout-class (or array of such types) or reference, and has no virtual functions (10.3) and no virtual base classes (10.1), and has the same access control (clause 11) for all non-static data members, and has no non-standard-layout base classes, and either has no non-static data member in the most-derived class and at most one base class with non-static data members, or has no base classes with non-static data members, and has no base classes of the same type as the first non-static data member. Sounds like working with something like this would tie my hands a bit with no virtual methods in the accessors or the node. Yet C++11 apparently has std::is_standard_layout to keep things checked. Can this be done safely? Appears to work in gcc-4.7, but I'd like to be sure I'm not invoking undefined behavior.

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  • How to programmatically launch a chromecast app from command line

    - by pushmatrix
    I want to launch a Chromecast app but NOT using the chrome extension or iOS or Android. Doing this from command line. I noticed that you can send a POST to your chromecast, and it will launch an app. For example if I do curl -H “Content-Type: application/json” http://CHROMECAST_IP:8008/apps/YouTube -X POST -d ‘v=oHg5SJYRHA0' Then it will start up youtube. But for some reason I can't do this with custom apps (in dev mode). I thought I'd be able to send a POST to http://CHROMECAST_IP:8008/apps/MY_REGISTERED_APP_ID, but no luck. I just get a 404 response. Hmmm... My app is just a simple webpage (it is not streamed media). I want to run a little headless server that starts my chromecast app everyday via a CRON task. Any help is greatly appreciated! Thanks :)

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  • C# enum to string auto-conversion?

    - by dcompiled
    Is it possible to have the compiler automatically convert my Enum values to strings so I can avoid explicitly calling the ToString method every time. Here's an example of what I'd like to do: enum Rank { A, B, C } Rank myRank = Rank.A; string myString = Rank.A; // Error: Cannot implicitly convert type 'Rank' to 'string' string myString2 = Rank.A.ToString(); // OK: but is extra work

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  • Does dynamic_cast work inside overloaded operator delete ?

    - by iammilind
    I came across this: struct Base { void* operator new (size_t); void operator delete (void*); virtual ~Base () {} // <--- polymorphic }; struct Derived : Base {}; void Base::operator delete (void *p) { Base *pB = static_cast<Base*>(p); if(dynamic_cast<Derived*>(pB) != 0) { /* ... NOT reaching here ? ... */ } free(p); } Now if we do, Base *p = new Derived; delete p; Surprisingly, the condition inside the Base::delete is not satisfied Am I doing anything wrong ? Or casting from void* looses the information of Derived* ?

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  • Inheritence and usage of dynamic_cast

    - by Mewzer
    Hello, Suppose I have 3 classes as follows (as this is an example, it will not compile!): class Base { public: Base(){} virtual ~Base(){} virtual void DoSomething() = 0; virtual void DoSomethingElse() = 0; }; class Derived1 { public: Derived1(){} virtual ~Derived1(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD1DoSomething{ ... } }; class Derived2 { public: Derived2(){} virtual ~Derived2(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD2DoSomething{ ... } }; I want to create an instance of Derived1 or Derived2 depending on some setting that is not available until run-time. As I cannot determine the derived type until run-time, then do you think the following is bad practice?... class X { public: .... void GetConfigurationValue() { .... // Get configuration setting, I need a "Derived1" b = new Derived1(); // Now I want to call the special DoSomething for Derived1 (dynamic_cast<Derived1*>(b))->SpecialD1DoSomething(); } private: Base* b; }; I have generally read that usage of dynamic_cast is bad, but as I said, I don't know which type to create until run-time. Please help!

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  • Way to get unsigned char into a std::string without reinterpret_cast?

    - by WilliamKF
    I have an unsigned char array that I need in a std::string, but my current way uses reinterpret_cast which I would like to avoid. Is there a cleaner way to do this? unsigned char my_txt[] = { 0x52, 0x5f, 0x73, 0x68, 0x7e, 0x29, 0x33, 0x74, 0x74, 0x73, 0x72, 0x55 } unsigned int my_txt_len = 12; std::string my_std_string(reinterpret_cast<const char *>(my_txt), my_txt_len);

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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • C#: how to construct strings

    - by Craig Johnston
    Which of these will achieve the correct result: (1) int X = 23; string str = "HELLO" + X.ToString() + "WORLD"; (2) int X = 23; string str = "HELLO" + X + "WORLD"; (3) int X = 23; string str = "HELLO" + (string)X + "WORLD"; EDIT: The 'correct' result is to output: HELLO23WORLD

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  • How to use the boost lexical_cast library for just for checking input

    - by Inverse
    I use the boost lexical_cast library for parsing text data into numeric values quite often. In several situations however, I only need to check if values are numeric; I don't actually need or use the conversion. So, I was thinking about writing a simple function to test if a string is a double: template<typename T> bool is_double(const T& s) { try { boost::lexical_cast<double>(s); return true; } catch (...) { return false; } } My question is, are there any optimizing compilers that would drop out the lexical_cast here since I never actually use the value? Is there a better technique to use the lexical_cast library to perform input checking?

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  • How to check whether iterators form a contiguous memory zone?

    - by Vincent
    I currently have the following function to read an array or a vector of raw data (_readStream is a std::ifstream) : template<typename IteratorType> inline bool MyClass::readRawData( const IteratorType& first, const IteratorType& last, typename std::iterator_traits<IteratorType>::iterator_category* = nullptr ) { _readStream.read(reinterpret_cast<char*>(&*first), (last-first)*sizeof(*first)); return _readStream.good(); } First question : does this function seem ok for you ? As we read directly a block of memory, it will only work if the memory block from first to last is contiguous in memory. How to check that ?

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  • excplicitly casting constness in

    - by jimifiki
    With the following code void TestF(const double ** testv){;} void callTest(){ double** test; TestF(test); } I get this: error C2664: 'TestF' : cannot convert parameter 1 from 'double **' to 'const double **' I cannot understand why. Why test cannot be silently casted to const double**? Why should I do it explicitly? I know that TestF(const_cast<const double**>(test)) makes my code correct, but I feel this should be unnecessary. Are there some key concepts about const that I'm missing?

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  • Correct usage(s) of const_cast<>

    - by ereOn
    Hi, As a common rule, it is very often considered a bad practice to use const_cast<>() in C++ code as it reveals (most of the time) a flaw in the design. While I totally agree with this, I however wonder what are the cases were using const_cast<>() is ok and the only solution. Could you guys please give me some examples you know/you encountered ? Thank you very much.

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  • T-SQL Tuesday #31 - Logging Tricks with CONTEXT_INFO

    - by Most Valuable Yak (Rob Volk)
    This month's T-SQL Tuesday is being hosted by Aaron Nelson [b | t], fellow Atlantan (the city in Georgia, not the famous sunken city, or the resort in the Bahamas) and covers the topic of logging (the recording of information, not the harvesting of trees) and maintains the fine T-SQL Tuesday tradition begun by Adam Machanic [b | t] (the SQL Server guru, not the guy who fixes cars, check the spelling again, there will be a quiz later). This is a trick I learned from Fernando Guerrero [b | t] waaaaaay back during the PASS Summit 2004 in sunny, hurricane-infested Orlando, during his session on Secret SQL Server (not sure if that's the correct title, and I haven't used parentheses in this paragraph yet).  CONTEXT_INFO is a neat little feature that's existed since SQL Server 2000 and perhaps even earlier.  It lets you assign data to the current session/connection, and maintains that data until you disconnect or change it.  In addition to the CONTEXT_INFO() function, you can also query the context_info column in sys.dm_exec_sessions, or even sysprocesses if you're still running SQL Server 2000, if you need to see it for another session. While you're limited to 128 bytes, one big advantage that CONTEXT_INFO has is that it's independent of any transactions.  If you've ever logged to a table in a transaction and then lost messages when it rolled back, you can understand how aggravating it can be.  CONTEXT_INFO also survives across multiple SQL batches (GO separators) in the same connection, so for those of you who were going to suggest "just log to a table variable, they don't get rolled back":  HA-HA, I GOT YOU!  Since GO starts a new batch all variable declarations are lost. Here's a simple example I recently used at work.  I had to test database mirroring configurations for disaster recovery scenarios and measure the network throughput.  I also needed to log how long it took for the script to run and include the mirror settings for the database in question.  I decided to use AdventureWorks as my database model, and Adam Machanic's Big Adventure script to provide a fairly large workload that's repeatable and easily scalable.  My test would consist of several copies of AdventureWorks running the Big Adventure script while I mirrored the databases (or not). Since Adam's script contains several batches, I decided CONTEXT_INFO would have to be used.  As it turns out, I only needed to grab the start time at the beginning, I could get the rest of the data at the end of the process.   The code is pretty small: declare @time binary(128)=cast(getdate() as binary(8)) set context_info @time   ... rest of Big Adventure code ...   go use master; insert mirror_test(server,role,partner,db,state,safety,start,duration) select @@servername, mirroring_role_desc, mirroring_partner_instance, db_name(database_id), mirroring_state_desc, mirroring_safety_level_desc, cast(cast(context_info() as binary(8)) as datetime), datediff(s,cast(cast(context_info() as binary(8)) as datetime),getdate()) from sys.database_mirroring where db_name(database_id) like 'Adv%';   I declared @time as a binary(128) since CONTEXT_INFO is defined that way.  I couldn't convert GETDATE() to binary(128) as it would pad the first 120 bytes as 0x00.  To keep the CAST functions simple and avoid using SUBSTRING, I decided to CAST GETDATE() as binary(8) and let SQL Server do the implicit conversion.  It's not the safest way perhaps, but it works on my machine. :) As I mentioned earlier, you can query system views for sessions and get their CONTEXT_INFO.  With a little boilerplate code this can be used to monitor long-running procedures, in case you need to kill a process, or are just curious  how long certain parts take.  In this example, I added code to Adam's Big Adventure script to set CONTEXT_INFO messages at strategic places I want to monitor.  (His code is in UPPERCASE as it was in the original, mine is all lowercase): declare @msg binary(128) set @msg=cast('Altering bigProduct.ProductID' as binary(128)) set context_info @msg go ALTER TABLE bigProduct ALTER COLUMN ProductID INT NOT NULL GO set context_info 0x0 go declare @msg1 binary(128) set @msg1=cast('Adding pk_bigProduct Constraint' as binary(128)) set context_info @msg1 go ALTER TABLE bigProduct ADD CONSTRAINT pk_bigProduct PRIMARY KEY (ProductID) GO set context_info 0x0 go declare @msg2 binary(128) set @msg2=cast('Altering bigTransactionHistory.TransactionID' as binary(128)) set context_info @msg2 go ALTER TABLE bigTransactionHistory ALTER COLUMN TransactionID INT NOT NULL GO set context_info 0x0 go declare @msg3 binary(128) set @msg3=cast('Adding pk_bigTransactionHistory Constraint' as binary(128)) set context_info @msg3 go ALTER TABLE bigTransactionHistory ADD CONSTRAINT pk_bigTransactionHistory PRIMARY KEY NONCLUSTERED(TransactionID) GO set context_info 0x0 go declare @msg4 binary(128) set @msg4=cast('Creating IX_ProductId_TransactionDate Index' as binary(128)) set context_info @msg4 go CREATE NONCLUSTERED INDEX IX_ProductId_TransactionDate ON bigTransactionHistory(ProductId,TransactionDate) INCLUDE(Quantity,ActualCost) GO set context_info 0x0   This doesn't include the entire script, only those portions that altered a table or created an index.  One annoyance is that SET CONTEXT_INFO requires a literal or variable, you can't use an expression.  And since GO starts a new batch I need to declare a variable in each one.  And of course I have to use CAST because it won't implicitly convert varchar to binary.  And even though context_info is a nullable column, you can't SET CONTEXT_INFO NULL, so I have to use SET CONTEXT_INFO 0x0 to clear the message after the statement completes.  And if you're thinking of turning this into a UDF, you can't, although a stored procedure would work. So what does all this aggravation get you?  As the code runs, if I want to see which stage the session is at, I can run the following (assuming SPID 51 is the one I want): select CAST(context_info as varchar(128)) from sys.dm_exec_sessions where session_id=51   Since SQL Server 2005 introduced the new system and dynamic management views (DMVs) there's not as much need for tagging a session with these kinds of messages.  You can get the session start time and currently executing statement from them, and neatly presented if you use Adam's sp_whoisactive utility (and you absolutely should be using it).  Of course you can always use xp_cmdshell, a CLR function, or some other tricks to log information outside of a SQL transaction.  All the same, I've used this trick to monitor long-running reports at a previous job, and I still think CONTEXT_INFO is a great feature, especially if you're still using SQL Server 2000 or want to supplement your instrumentation.  If you'd like an exercise, consider adding the system time to the messages in the last example, and an automated job to query and parse it from the system tables.  That would let you track how long each statement ran without having to run Profiler. #TSQL2sDay

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  • T-SQL Tuesday #31 - Logging Tricks with CONTEXT_INFO

    - by Most Valuable Yak (Rob Volk)
    This month's T-SQL Tuesday is being hosted by Aaron Nelson [b | t], fellow Atlantan (the city in Georgia, not the famous sunken city, or the resort in the Bahamas) and covers the topic of logging (the recording of information, not the harvesting of trees) and maintains the fine T-SQL Tuesday tradition begun by Adam Machanic [b | t] (the SQL Server guru, not the guy who fixes cars, check the spelling again, there will be a quiz later). This is a trick I learned from Fernando Guerrero [b | t] waaaaaay back during the PASS Summit 2004 in sunny, hurricane-infested Orlando, during his session on Secret SQL Server (not sure if that's the correct title, and I haven't used parentheses in this paragraph yet).  CONTEXT_INFO is a neat little feature that's existed since SQL Server 2000 and perhaps even earlier.  It lets you assign data to the current session/connection, and maintains that data until you disconnect or change it.  In addition to the CONTEXT_INFO() function, you can also query the context_info column in sys.dm_exec_sessions, or even sysprocesses if you're still running SQL Server 2000, if you need to see it for another session. While you're limited to 128 bytes, one big advantage that CONTEXT_INFO has is that it's independent of any transactions.  If you've ever logged to a table in a transaction and then lost messages when it rolled back, you can understand how aggravating it can be.  CONTEXT_INFO also survives across multiple SQL batches (GO separators) in the same connection, so for those of you who were going to suggest "just log to a table variable, they don't get rolled back":  HA-HA, I GOT YOU!  Since GO starts a new batch all variable declarations are lost. Here's a simple example I recently used at work.  I had to test database mirroring configurations for disaster recovery scenarios and measure the network throughput.  I also needed to log how long it took for the script to run and include the mirror settings for the database in question.  I decided to use AdventureWorks as my database model, and Adam Machanic's Big Adventure script to provide a fairly large workload that's repeatable and easily scalable.  My test would consist of several copies of AdventureWorks running the Big Adventure script while I mirrored the databases (or not). Since Adam's script contains several batches, I decided CONTEXT_INFO would have to be used.  As it turns out, I only needed to grab the start time at the beginning, I could get the rest of the data at the end of the process.   The code is pretty small: declare @time binary(128)=cast(getdate() as binary(8)) set context_info @time   ... rest of Big Adventure code ...   go use master; insert mirror_test(server,role,partner,db,state,safety,start,duration) select @@servername, mirroring_role_desc, mirroring_partner_instance, db_name(database_id), mirroring_state_desc, mirroring_safety_level_desc, cast(cast(context_info() as binary(8)) as datetime), datediff(s,cast(cast(context_info() as binary(8)) as datetime),getdate()) from sys.database_mirroring where db_name(database_id) like 'Adv%';   I declared @time as a binary(128) since CONTEXT_INFO is defined that way.  I couldn't convert GETDATE() to binary(128) as it would pad the first 120 bytes as 0x00.  To keep the CAST functions simple and avoid using SUBSTRING, I decided to CAST GETDATE() as binary(8) and let SQL Server do the implicit conversion.  It's not the safest way perhaps, but it works on my machine. :) As I mentioned earlier, you can query system views for sessions and get their CONTEXT_INFO.  With a little boilerplate code this can be used to monitor long-running procedures, in case you need to kill a process, or are just curious  how long certain parts take.  In this example, I added code to Adam's Big Adventure script to set CONTEXT_INFO messages at strategic places I want to monitor.  (His code is in UPPERCASE as it was in the original, mine is all lowercase): declare @msg binary(128) set @msg=cast('Altering bigProduct.ProductID' as binary(128)) set context_info @msg go ALTER TABLE bigProduct ALTER COLUMN ProductID INT NOT NULL GO set context_info 0x0 go declare @msg1 binary(128) set @msg1=cast('Adding pk_bigProduct Constraint' as binary(128)) set context_info @msg1 go ALTER TABLE bigProduct ADD CONSTRAINT pk_bigProduct PRIMARY KEY (ProductID) GO set context_info 0x0 go declare @msg2 binary(128) set @msg2=cast('Altering bigTransactionHistory.TransactionID' as binary(128)) set context_info @msg2 go ALTER TABLE bigTransactionHistory ALTER COLUMN TransactionID INT NOT NULL GO set context_info 0x0 go declare @msg3 binary(128) set @msg3=cast('Adding pk_bigTransactionHistory Constraint' as binary(128)) set context_info @msg3 go ALTER TABLE bigTransactionHistory ADD CONSTRAINT pk_bigTransactionHistory PRIMARY KEY NONCLUSTERED(TransactionID) GO set context_info 0x0 go declare @msg4 binary(128) set @msg4=cast('Creating IX_ProductId_TransactionDate Index' as binary(128)) set context_info @msg4 go CREATE NONCLUSTERED INDEX IX_ProductId_TransactionDate ON bigTransactionHistory(ProductId,TransactionDate) INCLUDE(Quantity,ActualCost) GO set context_info 0x0   This doesn't include the entire script, only those portions that altered a table or created an index.  One annoyance is that SET CONTEXT_INFO requires a literal or variable, you can't use an expression.  And since GO starts a new batch I need to declare a variable in each one.  And of course I have to use CAST because it won't implicitly convert varchar to binary.  And even though context_info is a nullable column, you can't SET CONTEXT_INFO NULL, so I have to use SET CONTEXT_INFO 0x0 to clear the message after the statement completes.  And if you're thinking of turning this into a UDF, you can't, although a stored procedure would work. So what does all this aggravation get you?  As the code runs, if I want to see which stage the session is at, I can run the following (assuming SPID 51 is the one I want): select CAST(context_info as varchar(128)) from sys.dm_exec_sessions where session_id=51   Since SQL Server 2005 introduced the new system and dynamic management views (DMVs) there's not as much need for tagging a session with these kinds of messages.  You can get the session start time and currently executing statement from them, and neatly presented if you use Adam's sp_whoisactive utility (and you absolutely should be using it).  Of course you can always use xp_cmdshell, a CLR function, or some other tricks to log information outside of a SQL transaction.  All the same, I've used this trick to monitor long-running reports at a previous job, and I still think CONTEXT_INFO is a great feature, especially if you're still using SQL Server 2000 or want to supplement your instrumentation.  If you'd like an exercise, consider adding the system time to the messages in the last example, and an automated job to query and parse it from the system tables.  That would let you track how long each statement ran without having to run Profiler. #TSQL2sDay

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  • Fancy dynamic list in Android: TableLayout vs ListView

    - by Ralkie
    There is a requirement to have not-so-trivial dynamic list, each record of which consists of several columns (texts, buttons). It should look something like: Text11 Text12 Button1 Button2 Text21 Text22 Button1 Button2 ... At first obvious way to accomplish that seemed to be TableLayout. I was expecting to have layout/styling data specified in res/layout/*.xml and to populate it with some dataset from java code (as with ListView, for which its possible to specify TextView of item in *.xml and bind it to some array using ArrayAdapter). But after playing for a while, all I found to be possible is fully populating TableLayout programatically. Still, creating TableRow by TableRow and setting layout attributes directly in java code doesn't seem elegant enough. So the questions are: Am I at the right path? Is TableLayout really best View to accomplish that? Maybe it's more appropriate to extend ListView or something else to meet such requirements? Is it possible to have TableLayout/TableRow template specified in *.xml and data bound to this template in java side?

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  • Java - How to change context root of a dynamic web project in eclipse

    - by Yatendra Goel
    I have developed a dynamic web project in eclipse. Now I can access it through my browser using the following url: http://localhost:8080/MyDynamicWebApp Now I want to change the access url to http://localhost:8080/app I changed the context root from the project properties | Web Project Settings | Context Root But it is not working. The web app still has the access url as earlier. I have re-deployed the application on tomcat, re-started the tomcat and have done everything that should be done but the access url is the same as earlier. I found that there were no server.xml file attached with the WARfile. The how the tomcat is determining that the context root of my web app is /MyDynamicWebApp and is allowing me to access the application through that url

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  • Fields_for dynamic label

    - by sebajb
    I have dynamic form which has a set of values. I created a partial which contains text fields which I display. Next to each of them I would like to display a label containing the title of the text. For instance First Name, and Last Name would not be known previously. How do I go about doing that? It seems that I cannot access the attributes directly. But when I use the label field, the variable name in the label is displayed not the actual value.

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  • Dynamic Tree control in Flex 3

    - by nimmyliji
    I am looking for sample code to create a dynamic Tree control in Flex using a Collection of objects obtained from the backend(Perl cgi). So, initially the Tree will display the root nodes. Clicking root node, will invoke the data for populating the child nodes (basically adding child nodes on demand). Clicking child nodes will pull another collection add child nodes of child node. So, lets assume Initially the Tree will display - Root1 Root2 Root3 Clicking Root1 will display something like this - Root1 Child 1 Child 2 Root2 Root3 And Clicking Child1 will display - Root1 Child 1 Child1 of Child 1 Child2 of Child 1 Child 2 Root2 Root3 Is it possible? Thanks in advance...

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  • Can a DevExpress XtraGrid be filled using a a Dynamic SELECT statement string

    - by Gerhard Weiss
    Can a DevExpress XtraGrid be filled using a a Dynamic SELECT statement string? i.e. SELECT * FROM Employee or SELECT * FROM Dependents To fill our XtraGrids currently, we use a ORM that creates entities. To do this it takes a lot of steps and time. What is driving me to ask this question is we do a lot of client aquistions where we get hundreds of files. I do not want to create entities for all of these then have to create an XtraGrid for each entity. Ideally if I can just feed it a SELECT statement and the XtraGrid could render it then I could use the XtraGrid very nice data minipulation features (Filter, Group By, etc). If you have any other ideas or suggestions please to not hesitate to post them.

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  • FF extension: a popup with dynamic menuitems, with each menu item having another popup

    - by encryptor
    I am building an extension that has a popup whose elements are constructed by a function call everytime the mouse hovers over the popup option. I am able to achieve this. Now I need to have a popup for each of the menu item (inside the original popup) which is not dynamic though. I have this code, but it does not work: var myMenuPopup = document.getElementById("file-popup4"); for (var m=0; m var newItem = document.createElement("menupopup"); newItem.setAttribute("label", publicdisplayname[m]); newItem.setAttribute("id", "public" + m); var new1 = document.createElement("menuitem"); new1.setAttribute("label","Home"); new1.setAttribute("id", "publichome" + m); newItem.onclick = function(){ } newItem.appendChild(new1); myMenuPopup.appendChild(newItem); but this doesnt work. Can someone please help me out with whats the problem

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  • Dynamic find methods Vs conditional statements

    - by piemesons
    Student.find(:all, :conditions => [‘name = ? and status = ?’ ‘mohit’, 1]) Vs Student.find_all_by_name_and_status(‘mohit’, 1) Both the queries will result the same set of row but first one is preferable cause in the second way there will be exception generated method_missing and then rails will try to relate it as dynamic method. if fine then result set to returned. Can any body explain me this in a good manner. What exactly is happening behind the screen. Please correct me if i am wrong.

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