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  • Tips for optimizing C#/.NET programs

    - by Bob
    It seems like optimization is a lost art these days. Wasn't there a time when all programmers squeezed every ounce of efficiency from their code? Often doing so while walking 5 miles in the snow? In the spirit of bringing back a lost art, what are some tips that you know of for simple (or perhaps complex) changes to optimize C#/.NET code? Since it's such a broad thing that depends on what one is trying to accomplish it'd help to provide context with your tip. For instance: When concatenating many strings together use StringBuilder instead. If you're only concatenating a handful of strings it's ok to use the + operator. Use string.Compare to compare 2 strings instead of doing something like string1.ToLower() == string2.ToLower()

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  • Apply CSS Style on all elements except with a SPECIFIC ID

    - by Rajesh Paul
    CSS Code(what I need) <style> div[id!='div1']// I actually needed an inequality operator for NOT EQUAL TO { font-size:40px; } </style> HTML code <body> <div>abc</div> <div>def</div> <div id='div1'>ghi</div> </body> The CSS didn't work as I intended. I actually wanted to define the style for all <div>-elements except the one with id='div1'. How can I do that?

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  • readobject method throws ClassNotFoundException

    - by eruina
    Hi all, I'm trying to pick up Java and wanted to test around with Java's client/server to make the client send a simple object of a self defined class(Message) over to the server. The problem was that I kept getting a ClassNotFoundException on the server side. I think the rest of the codes seem to be alright because other objects such as String can go through without problems. I had two different netbeans projects in different locations for client and server each. Each of them have their own copy of Message class under their respective packages. Message class implements Serializable. On the client side, I attempt to send a Message object through. On the server side, upon calling the readObject method, it seems to be finding Message class from the client's package instead of it's own. printStackTrace showed: "java.lang.ClassNotFoundException: client.Message" on the server side I have not even tried to cast or store the object received yet. Is there something I left out?

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  • Intersection of two querysets in django

    - by unagimiyagi
    Hello, I can't do an AND on two querysets. As in, q1 & q2. I get the empty set and I do not know why. I have tested this with the simplest cases. I am using django 1.1.1 I have basically objects like this: item1 name="Joe" color = "blue" item2 name="Jim" color = "blue" color = "white" item3 name="John" color = "red" color = "white" Is there something weird about having a many-to-many relationship or what am I missing? queryset1 = Item.objects.filter(color="blue") this gives (item1, item2) queryset2 = Item.objects.filter(color="white") this gives (item2, item3) queryset1 & queryset2 gives me the empty set [] The OR operator works fine (I'm using "|" ) Why is this so?

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  • Does the JPQL avg aggregate function work with Integers?

    - by Kyle Renfro
    I have a JPA 2 Entity named Surgery. It has a member named transfusionUnits that is an Integer. There are two entries in the database. Executing this JPQL statement: Select s.transfusionUnits from Surgery s produces the expected result: 2 3 The following statement produces the expected answer of 5: Select sum(s.transfusionUnits) from Surgery s I expect the answer of the following statement to be 2.5, but it returns 2.0 instead. Select avg(s.transfusionUnits) from Surgery s If I execute the statement on a different (Float) member, the result is correct. Any ideas on why this is happening? Do I need to do some sort of cast in JPQL? Is this even possible? Surely I am missing something trivial here.

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  • Hiding members in a C struct

    - by Marlon
    I've been reading about OOP in C but I never liked how you can't have private data members like you can in C++. But then it came to my mind that you could create 2 structures. One is defined in the header file and the other is defined in the source file. // ========================================= // in somestruct.h typedef struct { int _public_member; } SomeStruct; // ========================================= // in somestruct.cpp #include "somestruct.h" typedef struct { int _public_member; int _private_member; } SomeStructSource; SomeStruct *SomeStruct_Create() { SomeStructSource *p = (SomeStructSource *)malloc(sizeof(SomeStructSource)); p->_private_member = 0xWHATEVER; return (SomeStruct *)p; } From here you can just cast one structure to the other. Is this considered bad practice? Or is it done often? (I think this is done with a lot of the structures when using the Win32 API, but you guys are the experts let me know!)

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  • How to read from a method that returns a filehandle in perl?

    - by Ryan Thompson
    I have an object with a method that returns a filehandle, and I want to read from that handle. The following doesn't work, because the right angle bracket of the method call is interpreted as the closing angle bracket of the input reader: my $input = <$object->get_handle()>; That gets parsed as: my $input = ( < $object- > ) get_handle() >; which is obviously a syntax error. Is there any way I can perform a method call within an angle operator, or do I need to break it into two steps like this? my $handle = $object->get_handle(); my $input = <$handle>;

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  • Subscribing to a ObservableCollection via reflection

    - by Julian Lettner
    How can I subscribe to a ObservableCollection<??> without knowing the element type of the collection? Is there a way to do this without too many 'magic strings'? This is a question for the .NET version 3.5. I think 4.0 would make my life much easier, right? Type type = collection.GetType(); if(type.IsGenericType && type.GetGenericTypeDefinition() == typeof(ObservableCollection<>)) { // I cannot cast the collection here ObservableCollection<object> x = collection; } Thanks for your time.

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  • how to get the size of a C global array into an assembly program written for the avr architecture co

    - by johannes
    I have a .c file with the following uint8_t buffer[32] I have a .S file where I want to do the following cpi r29, buffer+sizeof(buffer) The second argument for cpi muste be an imidiate value not a location. But unfortunetly sizeof() is a c operator. Both files, are getting compiled to seperate object files and linked afterwards. If I do avr-objdump -x file.c. Amongst other things, I get the size of the buffer. So it is already available in the object file. How do I access the size of the buffer in my assembly file at compile time?

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  • LINQ Expression<Func<T, bool>> equavalent of .Contains()

    - by BK
    Has anybody got an idea of how to create a .Contains(string) function using Linq Expressions, or even create a predicate to accomplish this public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) { var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>> (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters); } Something simular to this would be ideal?

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  • Warning: XXX may not respond to YYY

    - by Aurel300
    Hey, I am making some stuff in Objective-C++... And I must say that I am a total newbie when it comes to the Objective-C part... I don't really want to learn it, I kinda just need it for accessing a few Mac APIs (ObjC is such a dumb language). So - compiling with g++ -x objective-c++ - and I somehow keep getting this warning: XXX may not respond to YYY First it was with a NSScreen, now it is with a NSWindow: NSWindow may not respond to +initWithContentRect:styleMask:backing:defer: I saw somewhere that I should cast it to id, but didn't work, throwing absolutely cryptic errors... So - WHAT does this warning actually mean and HOW am I supposed to make it stop?

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  • Pointing to vectors

    - by Matt Munson
    #include <iostream> #include <vector> using namespace std; int main () { vector <int> qwerty; qwerty.push_back(5); vector <int>* p = &qwerty; cout << p[0]; //error: no match for 'operator<<' in 'std::cout << * p' } I'm generally unclear on how to use pointers with vectors, so I'm pretty mystified as to why this is not working. To my mind, this should print 5 to screen.

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  • Trying to put a generic MyObj<T, U> into an IList where U can be different between objects

    - by Sergio Romero
    I have the following class definition: public interface IItem{} public class FirstObject<T, U> : IItem { public U SomeProperty { get; private set; } } IList<IItem> myList = new List<IItem>(); I did it like this because U can be of different types. Now I want to iterate the list and get my items back, the problem is that I do not know how to cast them back to their original type so I can read the value of SomeProperty. Thanks for your help.

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  • C# implicit conversions

    - by Chris Boden
    Hello, I'm currently working on an application where I need to load data from an SQL database and then assign the retrieved values into the properties of an object. I'm doing this by using reflection since the property names and column names are the same. However, many of the properties are using a custom struct type that is basically a currency wrapper for the decimal type. I have defined an implicit conversion in my struct: public static implicit operator Currency(decimal d) { return new Currency(d); } This works fine when I use it in code. However, when I have this: foreach (PropertyInfo p in props) { p.SetValue(this, table.Rows[0][p.Name], null); } It throws an ArgumentException stating that it cannot convert from System.Decimal to Currency. I'm confused since it works fine in any other circumstance.

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  • what does this C++ line of code mean "sol<?=f((1<<n)-1,i,0)+abs(P[i])*price;"

    - by KItis
    Could anyone help me to understand following line of code. sol I am studying an algorithm written using c++ and it has following operator " following is the error message returned. Hello.cpp: In function ‘int main()’: Hello.cpp:115: error: ‘memset’ was not declared in this scope Hello.cpp:142: error: expected primary-expression before ‘?’ token Hello.cpp:142: error: expected primary-expression before ‘=’ token Hello.cpp:142: error: expected ‘:’ before ‘;’ token Hello.cpp:142: error: expected primary-expression before ‘;’ token may be " Thanks in advance for the time you spent reading this post.

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  • Deriving streambuf or basic_ostringstream?

    - by Helltone
    Hi, I want to derive a stringstream so that I can use the operator<< to construct a message which will then be thrown. The API would look like: error("some text") << " more text " << 42 << std::endl; This should do a throw "some text more text 42" So what I did is make an errorbuf (inheriting from streambuf) which overloads the 'overflow' method and then create an ostream(&errorbuf). I wonder if I shouldn't instead inherit from basic_ostringstream or something...

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  • How can I match at the beginning of any line, including the first, with a Perl regex?

    - by JoelFan
    According the the Perl documentation on regexes: By default, the "^" character is guaranteed to match only the beginning of the string ... Embedded newlines will not be matched by "^" ... You may, however, wish to treat a string as a multi-line buffer, such that the "^" will match after any newline within the string ... you can do this by using the /m modifier on the pattern match operator. The "after any newline" part means that it will only match at the beginning of the 2nd and subsequent lines. What if I want to match at the beginning of any line (1st, 2nd, etc.)? EDIT: OK, it seems that the file has BOM information (3 chars) at the beginning and that's what's messing me up. Any way to get ^ to match anyway? EDIT: So in the end it works (as long as there's no BOM), but now it seems that the Perl documentation is wrong, since it says "after any newline"

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  • matlab noninteger step indexing

    - by rlbond
    So, I have a vector: k = 1:100; And I want to take 19 elements from it, which are roughly equally-spaced. So I write this: m = k(1:(99/18):end); This works great, except for a tiny problem: Warning: Integer operands are required for colon operator when used as index m = 1 7 12 18 23 29 34 40 45 51 56 62 67 73 78 84 89 95 100 Now, I understand why this comes up, but I'd like to get rid of that warning. Is there a "right" way to do this without a warning?

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  • Google Datastore low-level api query by key property

    - by Keyur
    I'm using the low-level google datastore api and I want to query by the key property and another property (let's call it category). I need to query based on a list of keys for which I'll use the IN operator. I know that the max. number of values you can provide for the IN clause is 30. I have 2 questions: Does the limit of 30 IN values apply to the key property as well? Do I need to create a composite index on {_key_ + category} or just on {category} for this query? Thanks, Keyur

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  • Postgres column casting...

    - by Simon
    I have a query SELECT assetid, type_code, version, name, short_name, status, languages, charset, force_secure, created, created_userid, updated, updated_userid, published, published_userid, status_changed, status_changed_userid FROM sq_ast WHERE assetid = 7 which doesn't work and throws ERROR: operator does not exist: character varying = integer LINE 4: FROM sq_ast WHERE assetid = 7 I can get it to work by doing SELECT assetid, type_code, version, name, short_name, status, languages, charset, force_secure, created, created_userid, updated, updated_userid, published, published_userid, status_changed, status_changed_userid FROM sq_ast WHERE assetid = '7' Please note the quoting of the 7 in the WHERE clause... I am deploying an huge application and I cannot rewrite the core... similarly I don't want to risk changing the type of the column... I'm no Postgres expert... please help... Is there an option for strict casting of columns???

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  • Method hiding with interfaces

    - by fearofawhackplanet
    interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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  • How can I search for numbers in a varchar column

    - by dave
    I've got a simple nvarchar(25) column in an SQL database table. Most of the time, this field should contain alphanumeric text. However, due to operator error, there are many instances where it contains only a number. Can I do a simple search in SQL to identify these cases? That is, determine which rows in the table contain only digits in this column. As an extension, could I also search for those column values which contain only digits and a space and/or slash. In other languages (eg. Perl, Java) a regular expression would resolve this quickly and easily. But I haven't been able to find the equivalent in SQL.

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  • SQL vs MySQL: Rules about aggregate operations and GROUP BY

    - by Phazyck
    In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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  • VMware Workstation Bridged Network Host UnReachable

    - by user2097818
    VMware Workstation 7 on Win7-64 (Home Premium). I have confirmed this on any guest running on this machine (from winxp to debian). I am using a bridged network connection for my guests (Automatic on VMnet0). All of the network configuration is done with DHCP (including on the host). Problem What I can not do: Ping my host machine from inside any VM. (either shows me "Destination Host Unreachable" or will just timeout) What I CAN do right after power up, with no problems at all. I can connect to the internet from inside the VM I can ping my router from inside the VM I can ping other machines on my network from inside the VM Other machines can ping the VM Other machines can ping the host My host machine can ping the VM (this one is important. read further) Details So I have my router assigned as 192.168.2.1/255.255.255.0, and the router provides the DHCP service (and it seems to be doing so successfully). There are no IP conflicts on the network that I am aware of. All Gateways and Subnet masks are appropriate and matching. My entire workshop is on one single subnet, with one single DHCP server and gateway. There is one method in which I can ping successfully, but it requires an active connection initiated from the host (I start pinging from host to VM). During the period of the active connection, I can successfully ping from VM to host, using explicit IP address. As soon as the host connection is closed, the VM ping starts hanging with the same old messages. My Thoughts This really feels like a firewall problem, but I have turned off all firewalls on host and VM, powered down the network, powered back up, and the problem still persists. And if it was firewall, why would only the IP address associated with bridged VM networks be blocked. I feel as though my host operating system (Win7) is somehow configured incorrectly, or, VMware Workstation is configured incorrectly from the host side. Although I have done my best to put everything in default, I feel like I am missing something silly.

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  • Play 2.0 RESTful request post-processing

    - by virtualeyes
    In regard to this question I am curious how one can do post-request REST processing a la (crude): def postProcessor[T](content: T) = { request match { case Accepts.Json() => asJson(content) case Accepts.Xml() => asXml(content) case _ => content } } overriding onRouteRequest in Global config does not appear to provide access to body of the response, so it would seem that Action composition is the way to go to intercept the response and do post-processing task(s). Question: is this a good idea, or is it better to do content-type casting directly within a controller (or other class) method where the type to cast is known? Currently I'm doing this kind of thing everywhere: toJson( i18n("account not found") ) toJson( Map('orderNum-> orderNum) ) while I'd like the toJson/toXml conversion to happen based on accepts header post-request.

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