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• Multi-client C# ODBC (Sybase/Oracle/MSSQL) table access question.

  - by Hamish Grubijan

  I am working on a feature that would allow clients pick a unique identifier (ci_name). The code below is a generic version that gets expanded to the right sql depending on the vendor. Hopefully it makes sense. #include "sql.h" create table client_identification ( ci_id TYPE_ID IDENTITY, ci_name varchar(64) not null, constraint ci_pk primary key (ci_name) ); go CREATE_SEQUENCE(ci_id) There will be simple stored procedures for adding, retrieving, and deleting these user records. This will be used by several admins. This will not happen very frequently, but there is still a possibility that something will be added or deleted since the list was initially retrieved. I have not yet decided if I need to detect the case of a double delete, but the user name cannot be created twice - primary key constraint will object. I want to be able to detect this particular case and display something like: "you snooze - you loose." :) I would like to leverage the pk constraint instead of doing some extra sql gymnastics. So, how can I detect this case cleanly, so that it works in MS SQL 2008, Sybase, and Oracle? I hope to do better than catch a general ODBC exception and parse out the text and look for what Sybase, Oracle, and MSSQL would give me back. Oracle is a little different. We actually prepend these variables to the Oracle version of stored procedures because they are not available otherwise: Vret_val out number, Vtran_count in out number, Vmessage_count in out number, Thanks. General helpful tips and comments are welcome, except for naming convention ones ( I do not have a choice here, plus I mangled the actual names a bit).

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• Implicit conversion between Scala collection types

  - by ebruchez

  I would like to implicitly convert between the Scala XML Elem object and another representation of an XML element, in my case dom4j Element. I wrote the following implicit conversions: implicit def elemToElement(e: Elem): Element = ... do conversion here ... implicit def elementToElem(e: Element): Elem = ... do conversion here ... So far so good, this works. Now I also need collections of said elements to convert both ways. First, do I absolutely need to write additional conversion methods? Things didn't seem to work if I didn't. I tried to write the following: implicit def elemTToElementT(t: Traversable[Elem]) = t map (elemToElement(_)) implicit def elementTToElemT(t: Traversable[Element]) = t map (elementToElem(_)) This doesn't look too ideal because if the conversion method takes a Traversable, then it also returns a Traversable. If I pass a List, I also get a Traversable out. So I assume the conversion should be parametrized somehow. So what's the standard way of writing these conversions in order to be as generic as possible?

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• How should I link two items with MouseMovementListeners?

  - by user1708810

  I'm working on a program that will display two "views" of the same set of items. So I need to have something set up so that when the top down view is changed, the side view is updated (and vice versa). Here's a brief outline of the relevant code so you can get an idea of my structure so far: public class DraggableComponent extends JComponent { //Contains code for MouseMovementListener that makes the item draggable } public class ItemGraphic extends DraggableComponent { //Code to render the graphic } public class Item { private ItemGraphic topGraphic; private ItemGraphic sideGraphic; } I'm able to get each graphic to display fine in my GUI. I can also independently drag each graphic. I'm missing the "linking." Some ideas I've been thinking about: Have one listener for the whole GUI. Loop through each Item and if the cursor is within the bounds of either graphic, move the other graphic. I'm concerned about the efficiency of this method. Multiple "paired" listeners (not quite sure how this would work, but the idea is that each graphic would have a listener for the other paired graphic)

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• Entity and N-Tier architecture in C#

  - by acadia

  Hello, I have three tables as shown below Emp ---- empID int empName deptID empDetails ----------- empDetailsID int empID int empDocuments -------------- docID empID docName docType I am creating a entity class so that I can use n-tier architecture to do database transactions etc in C#. I started creating class for the same as shown below using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace employee { class emp { private int empID; private string empName; private int deptID; public int EmpID { get; set; } public string EmpName { get; set; } public int deptID { get; set; } } } My question is as empDetails and empDocuments are related to emp by empID. How do I have those in my emp class. I would appreciate if you can direct me to an example. Thanks

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• How can I programmatically position a view using relative points?

  - by Steve Madsen

  What is the best way to position a view relative to the size of its superview, when the bounds of the superview are not yet known? I am trying to avoid hard-coding coordinates if it is at all possible. Perhaps this is silly, and if so, that's a perfectly acceptable answer. I've run into this many times when working with custom UI. The most recent example is that I'm trying to replace the UINavigationItem plain-text title with a custom view. I want that view to fill the superview, but in addition, I want a UIActivityIndicatorView on the right side, inset about 2 pixels and centered vertically. Here's the code: - (void) viewDidLoad { [super viewDidLoad]; customTitleView = [[UIView alloc] initWithFrame:CGRectZero]; customTitleView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; titleLabel = [[UILabel alloc] initWithFrame:CGRectZero]; titleLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth; titleLabel.lineBreakMode = UILineBreakModeWordWrap; titleLabel.numberOfLines = 2; titleLabel.minimumFontSize = 11.0; titleLabel.font = [UIFont systemFontOfSize:17.0]; titleLabel.adjustsFontSizeToFitWidth = YES; [customTitleView addSubview:titleLabel]; spinnerView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite]; spinnerView.center = CGPointMake(customTitleView.bounds.size.width - (spinnerView.bounds.size.width / 2) - 2, customTitleView.bounds.size.height / 2); spinnerView.hidesWhenStopped = YES; [customTitleView addSubview:spinnerView]; self.navigationItem.titleView = customTitleView; [customTitleView release]; } Here's my problem: at the time that this code runs, customTitleView.bounds is still zeroes. The auto-resizing mask hasn't had a chance to do its thing yet, but I very much want those values so that I can compute the relative positions of other sub-views (here, the activity indicator). Is this possible without being ugly?

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• Rails: Obfuscating Image URLs on Amazon S3? (security concern)

  - by neezer

  To make a long explanation short, suffice it to say that my Rails app allows users to upload images to the app that they will want to keep in the app (meaning, no hotlinking). So I'm trying to come up with a way to obfuscate the image URLs so that the address of the image depends on whether or not that user is logged in to the site, so if anyone tried hotlinking to the image, they would get a 401 access denied error. I was thinking that if I could route the request through a controller, I could re-use a lot of the authorization I've already built into my app, but I'm stuck there. What I'd like is for my images to be accessible through a URL to one of my controllers, like: http://railsapp.com/images/obfuscated?member_id=1234&pic_id=7890 If the user where to right-click on the image displayed on the website and select "Copy Address", then past it in, it would be the SAME url (as in, wouldn't betray where the image is actually hosted). The actual image would be living on a URL like this: http://s3.amazonaws.com/s3username/assets/member_id/pic_id.extension Is this possible to accomplish? Perhaps using Rails' render method? Or something else? I know it's possible for PHP to return the correct headers to make the browser think it's an image, but I don't know how to do this in Rails... UPDATE: I want all users of the app to be able to view the images if and ONLY if they are currently logged on to the site. If the user does not have a currently active session on the site, accessing the images directly should yield a generic image, or an error message.

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• Android - Memory leak when dynamically building UI with image resource backgrounds

  - by Rich

  I have an Activity that I swear is leaking memory. The app I'm working on does a lot with images, so I've had to be pretty stingy with memory when working directly with Bitmaps. I added an Activity, and now if you use this new Activity it basically puts me over the edge with mem usage and I end up throwing the "Bitmap exceeds VM budget" exception. If you never launch this Activity, everything is smooth as it was previously. I started reading about memory leaks, and I think that I have a similar situation to what is described in the article in the Android docs. I'm dynamically creating a bunch of image views and adding a BackgroundDrawable from the resources and adding an OnClickListener as well. I imagine I have to do some cleanup when the Activity hits onPause in its life cycle, but I'd like to know specifically what is the correct way. Here is the code that should demonstrate the objects I'm working with... LinearLayout templateContainer; . . . ImageView imgTemplatePreview = (ImageView) item.findViewById(R.id.imgTemplatePreview); . . . imgTemplatePreview.setBackgroundDrawable(getResources().getDrawable(previewId)); imgTemplatePreview.setOnClickListener(imgClick); templateContainer.addView(item);

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• Should I learn to code?

  - by saltcod

  Hi All, This is more of a philosophical question than a technical one, but I’d like some opinions on it, and I think that there are many others in my position that would benefit. My issue is that I don’t really have time to learn how to code. I know, I know… no one has time anymore, but please hear me out. Since learning to use Drupal about 2 years ago I’ve been involved with several projects wherein I’ve become the default quasi-developer, front-end designer, site manager, and system administrator. What I’ve found is that I can produce fairly nice, feature rich Drupal sites with the wealth of contrib. modules out there (Views, CCK, image handling, etc….). BUT! I can’t code. I know enough PHP to insert something into a block, or re-word a string, but that’s about it. I still don’t really even know how arrays work. My question Succinctly, my question is: Given the time that I have available for all of this stuff – in addition to a full-time job and regular life – am I better off trying to become more expert at the front-end stuff, or should I just learn PHP already? Pros 1. If a project doesn’t use Drupal, I’ll know enough PHP to be able to participate. 2. Learning PHP would help my Drupal development too 3. Learning PHP would make front-end theming easier 4. Learning PHP should give me that missing background in programming – and should allow me to learn other languages in the future Cons 1. At 28, I know I’m not too old to learn anything. But am I too old to become ‘good’? 2. Am I better off getting better and better at front-end UX work? 3. Am I better off farming out the PHP work? Suggestions from coders welcome! Thanks Terry

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• Looking for Simplified Overview of EJB3

  - by sdoca

  Hi I'm looking for a simplified overview of EJB3 components. I seem to understand most of the pieces of the puzzle, but can't quite get them to fit together in my brain as a full picture. I've developed numerous web applications (wars) that have been deployed on Tomcat before, but not a full-fledged EE application (ear). I would like the overview to be as generic as possible. I'm not looking for a tutorial on how to set up EJB3 on Glassfish built in NetBeans or some other vendor specific tutorial that's more about the IDE than the technology. I keep reading about Java, ejb-jar, web and ear modules but am not clear on what these different modules contain and how to use them to put together my app. In my case, I want to write a simple database CRUD web application. The first step is simple; create entity classes that model the database tables my app will be using. I plan on using annotations. Should I create a jar that contains just these enity classes? Is this the ejb-jar module (sometimes referred to as the Java module)? Next, I'll need some business logic classes that make use of the entity classes. These are the session beans (stateless or stateful) correct? Should these be packaged in the same jar as the entity classes or a separate jar? Finally, I'll need some sort of web interface (I'll be creating a JSF portlet) application that makes use of the both the session and entity beans. Together with the above jar(s), this will be my war? Assuming the above to be correct, what is involved in creating an ear? Forgive me if this post is vague, but I'm having a hard time defining what it is I don't understand. Thanks for any help!

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• Rails : can't write unknown attribute `url'

  - by user2954789

  I am new to ruby on rails,and I am learning by creating a blog. I am not able to save to my blogs table and I get this error "can't write unknown attribute url" Blogs migration :db/migrate/ class CreateBlogs < ActiveRecord::Migration --def change --- create_table :blogs do |t| ---- t.string :title ---- t.text :description ---- t.string :slug ---- t.timestamps --- end --end end Blogs Model :/app/models/blogs.rb class Blogs < ActiveRecord::Base --acts_as_url :title --def to_param ---url --end --validates :title, presence:true end Blogs Controller : /app/controllers/blogs_controller.rb class BlogsController < ApplicationController before_action :require_login --def new --- @blogs = Blogs.new --end --def show ---@blogs = Blogs.find(params[:id]) --end --def create ---@blogs = Blogs.new(blogs_params) --if @blogs.save ---flash[:success] = "Your Blog has been created." ---redirect_to home_path --else ---render 'new' --end -end --def blogs_params ---params.require(:blogs).permit(:title,:description) --end private --def require_login ---unless signed_in? ----flash[:error] = "You must be logged in to create a new Blog" ----redirect_to signin_path ---end --end end Blogs Form:/app/views/blogs/new.html.erb Blockquote <%= form_for @blogs, url: blogs_path do |f| %><br/> <%= render 'shared/error_messages_blogs' %><br/> <%= f.label :title %><br/> <%= f.text_field :title %><br/> <%= f.label :description %><br/> <%= f.text_area :description %><br/> <%= f.submit "Submit Blog", class: "btn btn-large btn-primary" %><br/> <% end %><br/> and I have also added "resources :blogs" to my routes.rb file. I get this error in controller at if @blogs.save

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• Using Generics to return a literal string or from Dictionary<string, object>

  - by Mike

  I think I outsmarted myself this time. Feel free to edit the title also I could not think of a good one. I am reading from a file and then in that file will be a string because its like an xml file. But in the file will be a literal value or a "command" to get the value from the workContainer so <Email>[email protected]</Email> or <Email>[? MyEmail ?]</Email> What I wanted to do instead of writing ifs all over the place to put it in a generic function so logic is If Container command grab from container else grab string and convert to desired type Its up to the user to ensure the file is ok and the type is correct so another example is so <Answer>3</Answer> or <Answer>[? NumberOfSales ?]</Answer> This is the procedure I started to work on public class WorkContainer:Dictionary<string, object> { public T GetKeyValue<T>(string Parameter) { if (Parameter.StartsWith("[? ")) { string key = Parameter.Replace("[? ", "").Replace(" ?]", ""); if (this.ContainsKey(key)) { return (T)this[key]; } else { // may throw error for value types return default(T); } } else { // Does not Compile if (typeof(T) is string) { return Parameter } // OR return (T)Parameter } } } The Call would be mail.To = container.GetKeyValue<string>("[email protected]"); or mail.To = container.GetKeyValue<string>("[? MyEmail ?]"); int answer = container.GetKeyValue<int>("3"); or answer = container.GetKeyValue<int>("[? NumberOfSales ?]"); But it does not compile?

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• C#: Populating a UI using separate threads.

  - by Andrew

  I'm trying to make some sense out of an application Ive been handed in order to track down the source of an error. Theres a bit of code (simplified here) which creates four threads which in turn populate list views on the main form. Each method gets data from the database and retrieves graphics from a resource dll in order to directly populate an imagelist and listview. From what Ive read on here (link) updating UI elements from any thread other than the UI thread should not be done, and yet this appears to work? Thread t0 = new Thread(new ThreadStart(PopulateListView1)); t0.IsBackground = true; t0.Start(); Thread t1 = new Thread(new ThreadStart(PopulateListView2)); t1.Start(); Thread t2 = new Thread(new ThreadStart(PopulateListView3)); t2.Start(); Thread t3 = new Thread(new ThreadStart(PopulateListView4)); t3.Start(); The error itself is a System.InvalidOperationException "Image cannot be added to the ImageList." which has me wondering if the above code is linked in some way. Iis this method of populating the UI recommended and if not what are the possible complications resulting from it?

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• What is a simple way to add a timer to a method

  - by John

  The following is in C#. I'm trying to do something very simple (I think). I have a method that loads an XML document XDocument doc = XDocument.Load(uri); , but I don't want to tie up pc resources if there are issues (connectivity, document size, etc.). So I'd like to be able to add a timeout variable that will cut the method off after a given number of seconds. I'm a newbie when it comes to asynchronous programming and find it confusing that there are so many examples written so many different ways . . . and none of them appear simple. I'd like a simple solution, if possible. Here's my thoughts so far on possible solution paths: 1) A method that wraps the existing load public XDocument LoadXDocument(string uri, int timeout){ //code } 2) A wrapper, but as an extension method XDocument doc = XDocument.LoadWithTimeout(string uri, int timeout); 3) A generic extension method. Object obj = SomeStaticClass.LoadWithTimeout(??? method, int timeout); 3), on its face seems really nice, because it would mean being able to generically add timeouts to many different method calls and not specifically tied to one type of object, but I suspect that it is either i)impossible or ii) very difficult. Please assist. Thanks.

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• Strange results while measuring delta time on Linux

  - by pachanga

  Folks, could you please explain why I'm getting very strange results from time to time using the the following code: #include <unistd.h> #include <sys/time.h> #include <time.h> #include <stdio.h> int main() { struct timeval start, end; long mtime, seconds, useconds; while(1) { gettimeofday(&start, NULL); usleep(2000); gettimeofday(&end, NULL); seconds = end.tv_sec - start.tv_sec; useconds = end.tv_usec - start.tv_usec; mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5; if(mtime > 10) printf("WTF: %ld\n", mtime); } return 0; } (You can compile and run it with: gcc test.c -o out -lrt && ./out) What I'm experiencing is sporadic big values of mtime variable almost every second or even more often, e.g: $ gcc test.c -o out -lrt && ./out WTF: 14 WTF: 11 WTF: 11 WTF: 11 WTF: 14 WTF: 13 WTF: 13 WTF: 11 WTF: 16 How can this be possible? Is it OS to blame? Does it do too much context switching? But my box is idle( load average: 0.02, 0.02, 0.3). Here is my Linux kernel version: $ uname -a Linux kurluka 2.6.31-21-generic #59-Ubuntu SMP Wed Mar 24 07:28:56 UTC 2010 i686 GNU/Linux

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• How to accommodate for the different screen resolution of iPhone 4?

  - by mystify

  This is a programming question! Read on before you vote to close! According to Apple, iPhone 4 has a new screen resolution: 3.5-inch (diagonal) widescreen Multi-Touch display 960-by-640-pixel resolution at 326 ppi This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. Edit: It seems Apple has integrated an switch that allows to tell if an app is highRes or not. Nice. When we develop high-resolution apps, probably they won't work on older devices. And if they did, they would suffer a lot from 4-times the size of any image, having to scale them down in memory. This is community wiki. Just add anything that you think is relevant to this huge problem (constant screen res was one of the main reasons why I didn't go for Android!!).

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• How can I take advantage of IObservable/IObserver to get rid of my "god object"?

  - by Will

  In a system I'm currently working on, I have many components which are defined as interfaces and base classes. Each part of the system has some specific points where they interact with other parts of the system. For example, the data readying component readies some data which eventually needs to go to the data processing portion, the communications component needs to query different components for their status for relaying to the outside, etc. Currently, I glue these parts of the system together using a "god object", or an object with intimate knowledge of different parts of the system. It registers with events over here and shuttles the results to methods over there, creates a callback method here and returns the result of that method over there, and passes many requests through a multi-threaded queue for processing because it "knows" certain actions have to run on STA threads, etc. While its convenient, it concerns me that this one type knows so much about how everybody else in the system is designed. I'd much prefer a more generic hub that can be given instances which can expose events or methods or callbacks or that can consume these. I've been seeing more about the IObservable/IObserver features of the reactive framework and that are being rolled into .NET 4.0 (I believe). Can I leverage this pattern to help replace my "god object"? How should I go about doing this? Are there any resources for using this pattern for this specific purpose?

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• Typedef equivalence in function arguments

  - by Warren Seine

  Hi guys, The question is kind of hard to ask without an example so here it is: #include <vector> struct O { }; struct C { template <typename T> void function1(void (C::*callback)(const O*)); template <typename T> void function2(void (C::*callback)(const typename T::value_type)); void print(const O*); }; int main() { C c; c.function1< std::vector<O*> >(&C::print); // Success. c.function2< std::vector<O*> >(&C::print); // Fail. } The error that I am given is: error: no matching function for call to ‘C::function2(void (C::*)(const O*))’. Basically, the only difference between calls is that in function2, I'm more generic since I use the typedef std::vector<O*>::value_type which should resolve to O*, hence similar to function1. I'm using G++ 4.2.1 (I know it's old), but Comeau confirms I'm wrong. Why does the compilation fail?

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• nservicebus deleting subscription record after inserting it?

  - by Justin Holbrook

  I have been playing with nservicebus for a few weeks now and since everything was going well on my local machine I decided to try to set up a test environment and work on deployment. I am using the generic host that comes with nservicebus and was using the nservicebus.Integration profile when running locally, but would like to use Nservicebus.Production in the test environment. I set up a sql server 2008 database, made changes to my app.config and everything seemed to work fine. But after a few attempts, I noticed messages were not being picked up by my subscriber. I checked the subscription table and it was empty. Upon examination of the logs I noticed the following: 2010-05-06 15:07:57,416 [1] DEBUG NHibernate.Persister.Entity.AbstractEntityPers ister [(null)] <(null) - Insert 0: INSERT INTO [Subscription] (SubscriberEndpo int, MessageType) VALUES (?, ?) 2010-05-06 15:07:57,416 [1] DEBUG NHibernate.Persister.Entity.AbstractEntityPers ister [(null)] <(null) - Update 0: 2010-05-06 15:07:57,416 [1] DEBUG NHibernate.Persister.Entity.AbstractEntityPers ister [(null)] <(null) - Delete 0: DELETE FROM [Subscription] WHERE Subscriber Endpoint = ? AND MessageType = ? Why would it insert then delete my subscription right afterwards? To try to rule out a nhibernate dialect issue I tried switching my subscription storage to an oracle 10g database. It behaved exactly the same, it worked the first 2 times, then I started seeing my subscriptions being deleted right after they were inserted. Any ideas what is causing this behavior?

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• Create table and call it from sql

  - by user1770816

  I have a PL/SQL function which creates a new temporary table. For creating the table I use execute immediate. When I run my function in oracle sql developer everything is ok; the function creates the temp table without errors. But when U use SQL: Select function_name from table_name I get an exceptions: ORA-14552: cannot perform a DDL, commit or rollback inside a query or DML ORA-06512: at "SYSTEM.GET_USERS", line 10 14552. 00000 - "cannot perform a DDL, commit or rollback inside a query or DML " *Cause: DDL operations like creation tables, views etc. and transaction control statements such as commit/rollback cannot be performed inside a query or a DML statement. Update Sorry, write from tablet PC and have problems with format text. My function: CREATE OR REPLACE FUNCTION GET_USERS ( USERID IN VARCHAR2 ) RETURN VARCHAR2 AS request VARCHAR2(520) := 'CREATE GLOBAL TEMPORARY TABLE '; BEGIN request := request || 'temp_table_' || userid || '(user_name varchar2(50), user_id varchar2(20), is_administrator varchar2(5)') || ' ON COMMIT PRESERVE ROWS'; EXECUTE IMMEDIATE (request); RETURN 'true'; END GET_USERS;

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• Using DisplayFor inside a display template

  - by Oenotria

  I've created a htmlhelper extension to reduce the amount of repetitive markup when creating forms: public static MvcHtmlString RenderField<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression) { return htmlHelper.DisplayFor(expression, "formfield"); } The idea being that inside my views I can just write @Html.RenderField(x=>x.MyFieldName) and it will print the label and the field's content with the appropriate div tags in place already. Inside the displaytemplates folder I have created formfield.cshtml containing the following: <div class="display-group"> <div class="display-label"> @Html.LabelFor(x => x) </div> <div class="display-field"> @Html.DisplayFor(x => x) </div> </div> Unfortunately it doesn't appear that it is possible to nest DisplayFor inside a display template (it doesn't render anything). I don't want to just using @Model because then I won't get checkboxes for boolean values, calendar controls for dates etc. Is there a good way around this?

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• Using deprecated binders and C++0x lambdas

  - by Sumant

  C++0x has deprecated the use of old binders such as bind1st and bind2nd in favor of generic std::bind. C++0x lambdas bind nicely with std::bind but they don't bind with classic bind1st and bind2nd because by default lambdas don't have nested typedefs such as argument_type, first_argument_type, second_argument_type, and result_type. So I thought std::function can serve as a standard way to bind lambdas to the old binders because it exposes the necessary typedefs. However, using std::function is hard to use in this context because it forces you to spell out the function-type while instantiating it. auto bound = std::bind1st(std::function<int (int, int)>([](int i, int j){ return i < j; }), 10); // hard to use auto bound = std::bind1st(std::make_function([](int i, int j){ return i < j; }), 10); // nice to have but does not compile. I could not find a convenient object generator for std::function. Something like std::make_fuction would be nice to have. Does such a thing exist? If not, is there any other better way of binding lamdas to the classic binders?

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• C# Convert string to nullable type (int, double, etc...)

  - by Nathan Koop

  I am attempting to do some data conversion. Unfortunately, much of the data is in strings, where it should be int's or double, etc... So what I've got is something like: double? amount = Convert.ToDouble(strAmount); The problem with this approach is if strAmount is empty, if it's empty I want it to amount to be null, so when I add it into the database the column will be null. So I ended up writing this: double? amount = null; if(strAmount.Trim().Length>0) { amount = Convert.ToDouble(strAmount); } Now this works fine, but I now have five lines of code instead of one. This makes things a little more difficult to read, especially when I have a large amount of columns to convert. I thought I'd use an extension to the string class and generic's to pass in the type, this is because it could be a double, or an int, or a long. So I tried this: public static class GenericExtension { public static Nullable<T> ConvertToNullable<T>(this string s, T type) where T: struct { if (s.Trim().Length > 0) { return (Nullable<T>)s; } return null; } } But I get the error: Cannot convert type 'string' to 'T?' Is there a way around this? I am not very familiar with creating methods using generics.

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• threading and getting COM port of attached phone

  - by I__

  i have the following code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } public class ThreadWork { public static void DoWork() { } } private void Form1_Load(object sender, EventArgs e) { ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork); Thread myThread = new Thread(myThreadDelegate); myThread.Start(); // Begin communications serialPort1.Open(); serialPort1.Write("AT+CMGF=1\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CNMI=2,2\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CSCA=\"+4790002100\"\r\n"); //Thread.Sleep(500); } private void serialPort1_DataReceived_1(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { string response = serialPort1.ReadLine(); this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n"))); } } } what i am trying to do is send AT COMMANDS to my phone which is attached to the computer through USB how do i know how to configure the properties of the serial port? (like which COM is the phone on [it's attached through USB], what about baudrate and databits?) when i run the program nothing really happens, i would like to send AT COMMANDS to my phone and the textbox is there to receive the response from my phone this is my first time using threads. am i using them correctly? what is the purpose of it in the current example? is it to just have a delay between send a response? what am i doing wrong?

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• How do I put all the types matching a particular C# interface in an IDictionary?

  - by Kevin Brassen

  I have a number of classes all in the same interface, all in the same assembly, all conforming to the same generic interface: public class AppleFactory : IFactory<Apple> { ... } public class BananaFactory : IFactory<Banana> { ... } // ... It's safe to assume that if we have an IFactory<T> for a particular T that it's the only one of that kind. (That is, there aren't two things that implement IFactory<Apple>.) I'd like to use reflection to get all these types, and then store them all in an IDictionary, where the key is typeof(T) and the value is the corresponding IFactory<T>. I imagine eventually we would wind up with something like this: _map = new Dictionary<Type, object>(); foreach(Type t in [...]) { object factoryForType = System.Reflection.[???](t); _map[t] = factoryForType; } What's the best way to do that? I'm having trouble seeing how I'd do that with the System.Reflection interfaces.

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• How can show data from another form

  - by Michael Quiles

  This is basically a tic tac toe game, and I have another form called Winner.cs when a player wins I want it to call the form (this part works) and then I want it to say xWinner.label =b1.text"" + has won the game!. the part I cant get to work is displaying the text in the winners form label. There's an example of a message box that commented out for reference instead of b1.text using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows.Forms; namespace MyGame { public class Result1 { static private int[,] Winners = new int[,] { {0,1,2}, {3,4,5}, {6,7,8}, {0,3,6}, {1,4,7}, {2,5,8}, {0,4,8}, {2,4,6}, }; static public bool CheckWinner(Button[] myControls) { bool gameOver = false; for (int i = 0; i < 8; i++) { int a = Winners[i, 0], b = Winners[i, 1], c = Winners[i, 2]; Button b1 = myControls[a], b2 = myControls[b], b3 = myControls[c]; if (b1.Text == "" || b2.Text == "" || b3.Text == "") continue; if (b1.Text == b2.Text && b2.Text == b3.Text) { b1.BackColor = b2.BackColor = b3.BackColor = System.Drawing.Color.LightCoral; b1.Font = b2.Font = b3.Font = new System.Drawing.Font("Microsoft Sans Serif", 32F, System.Drawing.FontStyle.Italic & System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0))); gameOver = true; Form xWinnerForm = new xWinnerForm(); xWinnerForm.Show(); //MessageBox.Show(b1.Text + " .... Wins the game!", "Game End", MessageBoxButtons.OK); //break; } } return gameOver; } } }

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