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• WPF DependencyProperty event before content changed

  - by morsanu

  First I will explain the context of the problem, because you might be able to point me in a better direction. I need to implement a undo-redo like system on an object. The object has a series of dependency properties. Some are double, int, string but some are also of DependencyObject type. I need to save the value of the property before it is changed, and for this I added the CoerceValueCallback. public static readonly DependencyProperty MyBackgroundProperty = DependencyProperty.Register("MyBackground", typeof(MyCustomizableBackground), typeof(MyComponent), new UIPropertyMetadata(default(MyCustomizableBackground), null, new CoerceValueCallback(OnPropertyChanged))); In OnPropertyChanged I save the value before it's changed. MyCustomizableBackground is the DependencyObject that has also some dependency properties. The problem is that in this case, where I have a custom object as a property, the OnPropertyChanged method isn't triggered, but when I have a common type, it is triggered.

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• WPF MVVM Pattern - References

  - by KroaX

  Hi everyone I wanted to know if some of you guys can post some articles, blog posts etc. that explain the MVVM Pattern in detail. There are not much explainations out there I think ( except Tutorials). I'm going to write my exam about WPF and also want to build in the MVVM Pattern. So I need some good references that are also digging a little deeper. I think I already have read a lot of texts about MVVM, but maybe you guys got some I didn't read yet. Would really appreciate if you would share your links to good and worth reading articles and explanations

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• Need help with SQL table structure transformation

  - by Arnis L.

  I need to perform update/insert simultaneously changing structure of incoming data. Think about Shops that have defined work time for each day of the week. Hopefully, this might explain better what I'm trying to achieve: worktimeOrigin table: columns: shop_id day val data: 123 | "monday" | "9:00 AM - 18:00" 123 | "tuesday" | "9:00 AM - 18:00" 123 | "wednesday" | "9:00 AM - 18:00" shop table: columns: id worktimeDestination.id worktimeDestination table: columns: id monday tuesday wednesday My aim: I would like to insert data from worktimeOrigin table into worktimeDestination and specify appropriate worktimeDestination for shop. shop table data: 123 1 (updated) worktimeDestination table data: 1 | "9:00 AM - 18:00" | "9:00 AM - 18:00" | "9:00 AM - 18:00" (inserted) Any ideas how to do that?

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• Google Street View API v3 : how can I avoid having "fish-eye" effect on Firefox?

  - by Benj

  I'm using google maps API V3 and I'm having trouble displaying correctly the street view within Firefox. I always get the "fish-eye" view (does not happen with Google chrome). So I assumed that the problem came from Firefox. I took a look to the street view options but found nothing. I would like to know if there is an option to have a flatten street view or if it is because Firefox does not support this kind of feature. If someone could explain it to me, I would be grateful. Below, what it looks in Firefox : And what it looks in Chrome :

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• Two '==' equality operators in same 'if' condition are not working as intended.

  - by Manav MN

  I am trying to establish equality of three equal variables, but the following code is not printing the obvious true answer which it should print. Can someone explain, how the compiler is parsing the given if condition internally? #include<stdio.h> int main() { int i = 123, j = 123, k = 123; if ( i == j == k) printf("Equal\n"); else printf("NOT Equal\n"); return 0; } Output: manav@workstation:~$ gcc -Wall -pedantic calc.c calc.c: In function ‘main’: calc.c:5: warning: suggest parentheses around comparison in operand of ‘==’ manav@workstation:~$ ./a.out NOT Equal manav@workstation:~$ EDIT: Going by the answers given below, is the following statement okay to check above equality? if ( (i==j) == (j==k))

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• c# xml string special characters

  - by sam

  Please help explain why the dataset cannot read the encoded xml? string xml = "<?xml version=\"1.0\" standalone=\"yes\" ?> <DataSet><node>it's my \"node\" & i like it</node></DataSet>"; string encodedXml = System.Security.SecurityElement.Escape(xml); DataSet ds = new DataSet(); ds.ReadXml(New XmlTextReader(new StringReader(encodedXml))); I have checked the link http://weblogs.sqlteam.com/mladenp/archive/2008/10/21/Different-ways-how-to-escape-an-XML-string-in-C.aspx What i want to do is to read a string with special characters into a dataset. But the code cannot locate the special characters in the string, c# added all the \ so the linenumber is not accurate generated by XmlException object. Anyone could provide the code to read a string with special characters into a dataset. thanks very much

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• explanation about prototype.js function binding code

  - by resopollution

  From: http://ejohn.org/apps/learn/#2 Function.prototype.bind = function(){ var fn = this, args = Array.prototype.slice.call(arguments), object = args.shift(); return function(){ return fn.apply(object, args.concat(Array.prototype.slice.call(arguments))); }; }; Can anyone tell me why the second return is necessary (before fn.apply)? Also, can anyone explain why args.concat is necessary? Why wouldn't it be re-written as: fn.apply(object, args) instead of return fn.apply(object, args.concat(Array.prototype.slice.call(arguments)));

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• Language Agnositc Basic Programming Question

  - by Rachel

  This is very basic question from programming point of view but as I am in learning phase, I thought I would better ask this question rather than having an misunderstanding or narrow knowledge about the topic. So do excuse me if somehow I mess it up. Question: Let say I have class A,B,C and D now class A has some piece of code which I need to have in class B,C and D so I am extending class A in class B, class C, and class D Now how can I access the function of class A in other classes, do I need to create an object of class A and than access the function of class A or as am extending A in other classes than I can internally call the function using this parameter. If possible I would really appreciate if someone can explain this concept with code sample explaining how the logic flows.

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• How do I use a shared library (in this case JsonCpp) in my C++ program on Linux?

  - by Not Joe Bloggs

  I'm a new-ish C++ programmer, and I'm doing my first program on my own using C++. I decided I would like to use JSON to store some of the data I'm going to be using, and I've found a library to handle JSON, JsonCpp. I've installed the library using my Linux system's package manager, and in my C++ code, I've used in my source code file #include <json> and compiled it using g++ and it's -ljson and -L/usr/lib options (libjson.so is located in /usr/lib). However, the first usage of Json::Value, an object provided by the library, gives a compilation error of "Json has not declared". I'm sure my mistake is something simple, so could someone explain what I'm doing wrong? None of the books I had mention how to use shared libraries, so I've had to google to find this much.

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• .NET: What is the purpose of the ProhibitDtd property in XmlReaderSettings? Why is DTD a security i

  - by Cheeso

  The documentation says: When set to true, the XmlReader throws an XmlException when any DTD content is encountered. Do not enable DTD processing if you are concerned about Denial of Service issues or if you are dealing with untrusted sources. If you have DTD processing enabled, you can use the XmlSecureResolver to restrict the resources that the XmlReader can access. You can also design your application so that the XML processing is memory and time constrained. For example, configure time-out limits in your ASP.NET application. Can someone please explain the issue? Why would a reader application want to prohibit the retrieval of a DTD? Where is the denial-of-service issue, if it is a reading application? What is the "trust" issue that is mentioned? Thanks

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• Owner Vs PArent and Taction shortcuts on Frames

  - by Fred

  I have a form with a panel. I create frames at runtime and display them on the panel by setting frame's parent property to the panel. When creating panels I do not set the owner property because i manage myself the lifetime of the frame. Until now i got no problem. Next I put an TActionList on the frame with some shortcuts on the actions. I found that my actions did not execute until I set the owner property of the frame to the panel. Can someone can explain me that ? I thought that owner property was just about wich component is responsible to free the children components, and not responsible to forward key events.

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• "Arbitrary" context free grammars?

  - by danwroy

  Long time admirer first time inquirer :) I'm working on a program which derives a deterministic finite-state automata from a context-free grammar, and the paper I have been assigned which explains how to do this keeps referring to "arbitrary probabilistic context-free grammars" but never defines the meaning of "arbitrary" in relation to PCFGs. I assume they mean "any old PCFG" but then why not just say "any PCFG"? The term also turns up in several Wikipedia entries. At the top of the CFG page there is a reference to arbitrariness in relation to CFGs on ("clauses can be nested inside clauses arbitrarily deeply"), but doesn't make clear why someone would refer to a PCFG or subset of PCFGs as arbitrary. In case anyone is curious, the paper is Parsing and Hypergraphs by Klein and Manning (2001); I've also been reading two other papers by them related to this one (An Agenda-Based Chart Parser for Arbitrary Probabilistic Context-Free Grammars and Empirical Bounds, Theoretical Models, and the Penn Treebank) which use the term extensively but never explain it either. Thanks for your help!

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• Releasing NSData causes exception...

  - by badmanj

  Hi, Can someone please explain why the following code causes my app to bomb? NSData *myImage = UIImagePNGRepresentation(imageView.image); : [myImage release]; If I comment out the 'release' line, the app runs... but a few times calling the function containing this code and I get a crash - I guess caused by a memory leak. Even if I comment EVERYTHING else in the function out and just leave those two lines, when the release executes, the app crashes. I'm sure this must be a newbie "you don't know how to clean up your mess properly" kind of thing ;-) Cheers, Jamie.

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• Can I set a property on an object that is only declared on the instance type, when I don't know the

  - by WilberBeast

  Let me explain. I have a List into which I am adding various ASP.NET controls. I then wish to loop through the list and set a CssClass, however not every Control supports the property CssClass. What I would like to do is test if the underlying instance type supports the CssClass property and set it, but I'm not sure how to do the conversion prior to setting the property since I don't know the type of each Control object. I know that I can use typeof or x.GetType(), but I'm not sure how to use these to convert the controls back to the instance type in order to test for and then set the property. Actually I seem to have solved this, so I thought that I would post the code here for others. foreach (Control c in controlList) { PropertyInfo pi = c.GetType().GetProperty("CssClass"); if (pi != null) pi.SetValue(c, "desired_css_class", null); } I hope that this helps someone else as I has taken me hours to research these 2 lines of code. Cheers Steve

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• I cant really wrap my head around BOOLEAN logic when I use NOT together with AND and OR

  - by Bq

  Im trying to understand how boolean logic works when I use NOT. To give an example using awk I have a text file containing CORE PORT CORE PORT COREPORT CORE COREPORT And I would like to remove all COREPORT lines. The way I thought I would do it was with (NOT CORE) AND (NOT PORT) eg awk '/!CORE/&&/!PORT/{print}' But when I try it out Im actually supposed to use OR instead of AND awk '/!CORE/||/!PORT/{print}' I would be really glad if some one could explain where my thinking is wrong and super glad if it could be visualized with a venn diagram or something like the boolean machine at kathyschrock

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• Height of tableHeaderView seems to be 0

  - by gabac

  I tried to override the second tableHeaderView. But it seems that the height of it in the method heightForHeaderInSection seems to be 0. Can't explain it, do I have to put it in a iVar because in the viewForHeaderInSection I can set the view without any problems. - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section { if(section == 0) return @"Adding a new list"; else return @"Other lists"; } - (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section { if(section == 0) { return tableView.tableHeaderView; } else { UIView *view = [[[UIView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)] autorelease]; view.backgroundColor = [UIColor redColor]; return view; } } - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section { if(section == 0) return tableView.tableHeaderView.frame.size.height; else return 30; }

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• what is a data serialization system?

  - by Yang

  according to Apache AVRO project, "Avro is a serialization system". By saying data serialization system, does it mean that avro is a product or api? also, I am not quit sure about what a data serialization system is? for now, my understanding is that it is a protocol that defines how data object is passed over the network. Can anyone help explain it in an intuitive way that it is easier for people with limited distributed computing background to understand? Thanks in advance!

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• How to draw/manage a hexagon grid?

  - by W.N.

  I've read this article: generating/creating hexagon grid in C . But look like both the author and answerer have already abandoned it. v(hexagonSide - hexagonWidth * hexagonWidth): What's hexagonSide and hexagonWidth? Isn't it will < 0 (so square root can't be calculated). And, can I put a hexagon into a rectangle? I need to create a grid like this: One more thing, how can I arrange my array to store data, as well as get which cells are next to one cell? I have never been taught about hexagon, so I know nothing about it, but I can easily learn new thing, so if you can explain or give me a clue, I may do it myself.

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• What are pointers to class members used for?

  - by srikfreak

  I have read about pointers to class members, but I have never seen them being used in any practical applications. Can someone explain what are the use cases of such pointers? Is it really necessary to have such pointers? Eg. class abc { public: int a; abc(int val) { a = val; } }; int main { int abc::*data; abc obj(5); data = &abc::a; cout << "Value of a is " << obj.*data << endl; return 0; } In the above eg. why is the value of 'a' accessed in this manner? What is the advantage of using pointers to class members?

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• Why can XSLT not parse this XML?

  - by Matt W

  Taking the XSLT and XML from this page as an example: http://www.w3schools.com/xsl/xsl_transformation.asp I have an xml file which contains (above example modified): <?xml version="1.0" encoding="ISO-8859-1"?> <?xml-stylesheet type="text/xsl" href="cdcatalog.xsl"?> <catalog xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://tempuri.org/"> <cd> In my case, the output contains nothing when the XSLT/XML is processed by the browser. The moment I remove the attributes from the element, it works. Problem is, I don't really have the option of pre-processing those attributes out of the file. Can anyone explain how to force the XSLT to work with the XML as is, please? After all, those attributes seem fairly standard. Many thanks, Matt.

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• Tokenize problem in Java with separator ". "

  - by user112976

  I need to split a text using the separator ". ". For example I want this string : Washington is the U.S Capital. Barack is living there. To be cut into two parts: Washington is the U.S Capital. Barack is living there. Here is my code : // Initialize the tokenizer StringTokenizer tokenizer = new StringTokenizer("Washington is the U.S Capital. Barack is living there.", ". "); while (tokenizer.hasMoreTokens()) { System.out.println(tokenizer.nextToken()); } And the output is unfortunately : Washington is the U S Capital Barack is living there Can someone explain what's going on?

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• What does "infinity" really mean on a connection timeout? Does it retry the connection?

  - by corgrath

  The difference between connection and read timeout, is that read specifies how long the data connection can be open until it automatically closesc, correct? A connection timeout specifies how long the socket should wait until a connection is established, correct? So if a connection timeout is set to "infinity" what does that really mean? Will it try to establish a connection and if no response is given (as on packets are lost? or port is down?) it will just idle? or will Could someone please explain the basics of network/socket timeouts? and in what situation can a client socket wait infinity?

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• free switch : what is tls_port ?

  - by kiruthika

  Hi all, I am beginner to free switch.I have gone through the configuration file vars.xml in free switch. In this I have seen the following configurations. <X-PRE-PROCESS cmd="set" data="internal_auth_calls=true"/> <X-PRE-PROCESS cmd="set" data="internal_sip_port=5070"/> <X-PRE-PROCESS cmd="set" data="internal_tls_port=5071"/> <X-PRE-PROCESS cmd="set" data="internal_ssl_enable=false"/> <X-PRE-PROCESS cmd="set" data="internal_ssl_dir=$${base_dir}/conf/ssl"/> In the above I am having the doubt with tls_port. What is the use of tls_port .I have searched about this in net and I have read that tls protocol is used for secure data transfer in network. So please explain me about the communication in freeswitch. Thanks in advance.

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• Single HTML Table from multiple MySQL tables

  - by David Chouinard

  Hi! I've been struggling for a while with this one; I'll try to explain it here as simply as possible. Consider this MySQL table: +----------+-----------+---------+--------+ |status_id |session_id |pilot_id |present | +----------+-----------+---------+--------+ |1 |61 |901 |1 | |2 |63 |901 |1 | |3 |62 |901 |0 | |4 |62 |902 |1 | |5 |63 |903 |1 | +----------+-----------+---------+--------+ Both session_id and pilot_id are foreign keys making reference to a primary key in another table. The same pilot_id can be associated with different session_id, but every pilot_id-session_id combination is unique. I need to make an HTML table (in PHP) that would display the data like this: +----------+---------+---------+---------+ | |61 |62 |63 | +----------+---------+---------+---------+ |901 |X | |X | |902 | |X | | |903 | | |X | +----------+---------+---------+---------+ Hence, rows are pilot_id and columns are session_id. When a pilot_id-session_id combination has a present value of 1, the corresponding cell should be checked. (ie. when the row-combination is zero or the combination does not exist in the MySQL table, nothing should appear in the HTML table) Phew. Any ideas? Thanks!

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• set variables in an MVC application?

  - by Melissa

  I am trying to learn about the Orchard MVC application. I see the following code but cannot understand what it is doing. Can someone explain what this: User.As<UserPart>().Record.UserName = value; means? public class UserEditViewModel { [Required] public string UserName { get { return User.As<UserPart>().Record.UserName; } set { User.As<UserPart>().Record.UserName = value; } } [Required] public string Email { get { return User.As<UserPart>().Record.Email; } set { User.As<UserPart>().Record.Email = value; } } public IContent User { get; set; } }

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