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• Powershell: Select-Object with additional calculated difference value

  - by David.Chu.ca

  Let me explain my question. I have a daily report about one PC's free space as in text file (sp.txt) like: DateTime FreeSpace(MB) ----- ------------- 03/01/2010 100.43 DateTime FreeSpace(MB) ----- ------------- 03/02/2010 98.31 .... Then I need to use this file as input to generate a report with difference of free space between dates: DateTime FreeSpace(MB) Change ----- ------------- ------ 03/01/2010 100.43 03/02/2010 98.31 2.12 .... Here are some codes I have to get above result without the additional "Change" calculation: Get-Content "C:\report\sp.txt" ` | where {$_.trim().length -gt 0 -and -not ($_ -like "Date*") -and -not ($_ -like "---*")} ` | Select-Object @{Name='DateTime'; expression={[DateTime]::Parse($_.SubString(0, 10).Trim())}}, ` @{Name='FreeSpace(MB)'; expression={$_.SubString(12, 12).Trim()}}, ` | Sort-Object DateTime ` | Select-Object DateTime, 'FreeSpace(MB)' |ft -AutoSize # how to add additional column Change to this Select-Object? My understanding is that Select-Object will return a collection of objects. Here I create this collection from an input text file(parse each line into parts: datetime and freespace(MB)). In order to calculate the difference between dates, I guess that I need to add additional calculated value to the result of the last Select-Object, or pipe the result to another Select-Object with the calculation as additional property or column. In order to do it, I need to get the previous row's FreeSpace value. Not sure if it is possible and how?

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• Creating a Custom Design-Time Environment

  - by Charlie

  Hello all, My question is related to the design-time support of WPF. From MSDN I read, The WPF Designer provides a framework and a public API which you can use to implement custom adorners, tools, property editors, and designers. But the vast majority of the examples I have found are trivial, and do not illustrate much concerning the creation of a customized designer in an existing WPF application. We have migrated our application from Windows Forms to WPF over the past year, and the next step will be to take an existing WinForms Panel designer, and rewrite it in WPF. Suffice it to say that this will be a huge project. But I don't even know where to begin. I am wondering if any of you have had similar experiences writing a customized designer for a WPF application, and what it was like. Even better, if you could compare and contrast the functionality between the WinForms designer and the WPF designer, or explain the transition from the former to the latter, that would be helpful. If you know of any simple examples that demonstrate a customized design environment (with custom controls, etc.) that would be extremely beneficial. All in all, I am just wondering if many people have undertaken this yet, and what their results have been. EDIT: To clarify, yes, I am talking about hosting a WPF designer. It appears that this may not even be possible, which is a huge setback. Here is a screenshot of our current WinForms designer. As you can see, it is used to create customized user interfaces. You can drag custom controls onto it and design them, then put the panel into a "run mode" in which all of the controls become functional. Short of spending months writing our designer, would this be possible in WPF? What about .NET 4.0 and VS2010? Will those add any designer functionality?

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• Activate COM object using website doesn't work in Windows 2003 server

  - by Tarun

  I have been trying really hard to activate and launch a COM object using an ASP.NET web application. The aspx website has a code-behind file that has a reference to this COM object (which is an actual application - a CAD software). When required, the VB code creates (or launches) the application. The complete set-up works in a Win-XP (32-bit) environment both under debugging using visual studio and when the website is accessed by an outside user (through IIS server in XP). But the same application doesn't get activated when it is hosted onto the Win-2003 (32-bit) IIS server. I get "Object reference not set to an instance of an object" error. The way I have setup in Win-XP was to grant ASP user and Internet guest user permissions to the COM object in the DCOM Config and since the windows firewall is enabled, I add the exe file (associated with the COM object) to the exception list. For the case of Win-2003 server, I add the Network Service permission to the COM object. But the setup doesn't seem to work at all. I am not sure what I am missing and how to get the application to launch. Any help will be greatly appreciated.

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• Powershell / .Net: Get a reference to an object returned by a method

  - by Dan Menes

  I am teaching myself PowerShell by writing a simple parser. I use the .Net framework class Collections.Stack. I want to modify the object at the top of the stack in place. I know I can pop() the object off, modify it, and then push() it back on, but that strikes me as inelegant. First, I tried this: $stk = new-object Collections.Stack $stk.push( (,'My first value') ) ( $stk.peek() ) += ,'| My second value' Which threw an error: Assignment failed because [System.Collections.Stack] doesn't contain a settable property 'peek()'. At C:\Development\StackOverflow\PowerShell-Stacks\test.ps1:3 char:12 + ( $stk.peek <<<< () ) += ,'| My second value' + CategoryInfo : InvalidOperation: (peek:String) [], RuntimeException + FullyQualifiedErrorId : ParameterizedPropertyAssignmentFailed Next I tried this: $ary = $stk.peek() $ary += ,'| My second value' write-host "Array is: $ary" write-host "Stack top is: $($stk.peek())" Which prevented the error but still didn't do the right thing: Array is: My first value | My second value Stack top is: My first value Clearly, what is getting assigned to $ary is a copy of the object at the top of the stack, so when I the object in $ary, the object at the top of the stack remains unchanged. Finally, I read up on teh [ref] type, and tried this: $ary_ref = [ref]$stk.peek() $ary_ref.value += ,'| My second value' write-host "Referenced array is: $($ary_ref.value)" write-host "Stack top is still: $($stk.peek())" But still no dice: Referenced array is: My first value | My second value Stack top is still: My first value I assume the peek() method returns a reference to the actual object, not the clone. If so, then the reference appears to be being replaced by a clone by PowerShell's expression processing logic. Can somebody tell me if there is a way to do what I want to do? Or do I have to revert to pop() / modify / push()?

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• iPhone: Get indexPath of Predicate Object

  - by Nic Hubbard

  I am using a predicate to find an object in core data. I can successfully find the object that I want, but I need to also get the indexPath of that object, so that I can push a details view in for that object. Currently I have the following code for getting my object: NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:[NSEntityDescription entityForName:@"Ride" inManagedObjectContext:self.managedObjectContext]]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"title = %@ AND addressFull = %@", view.annotation.title, view.annotation.subtitle]; [fetchRequest setPredicate:predicate]; NSMutableArray *sortDescriptors = [NSMutableArray array]; [sortDescriptors addObject:[[[NSSortDescriptor alloc] initWithKey:@"title" ascending:YES] autorelease]]; [sortDescriptors addObject:[[[NSSortDescriptor alloc] initWithKey:@"addressFull" ascending:YES] autorelease]]; [fetchRequest setSortDescriptors:sortDescriptors]; [fetchRequest setReturnsObjectsAsFaults:NO]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"title", @"addressFull", nil]]; NSError *error = nil; NSArray *fetchedItems = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; // Sohow what record we returned NSLog(@"%@",[fetchedItems objectAtIndex:0]); So, I can correctly get my object into an array. But how do I translate that object into an indexPath?

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• Flex - Flash Builder Design View not showing embedded fonts correctly

  - by Crusader

  Tools: Air 2, Flex SDK 4.1, Flash Builder, Halo component set (NO Spark being used at all) Fonts work perfectly when running the appliction, but not in design view. This effectively makes design view WORTHLESS because it's impossible to properly position components or labels without knowing what the true size is (it changes depending on font...) ... CSS included in root component like so: <fx:Style source="style.css"/> CSS file: /* CSS file */ @namespace mx "library://ns.adobe.com/flex/mx"; global { font-family:Segoe; font-size:14; color:#FFFFFF; } mx|Application, mx|VBox, mx|HBox, mx|Canvas { font-family:Segoe; background-color:#660000; border-color:#222277; color:#FFFFFF; } mx|Button { font-family:Segoe; fill-colors:#660000, #660000, #660000, #660000; color:#FFFFFF; } .... Interestingly (or buggily?), when I try pasting the style tag into a subcomponent (lower than the top level container), I get a bunch of warnings in the subcomponent editor view stating that CSS type selectors are not supported in.. (all the components in the style sheet). Yet, they do work when the application is executed. Huh? This is how I'm embedding the fonts in the root level container: [Embed(source="/assets/segoepr.ttf", fontName="Segoe", mimeType="application/x-font-truetype", embedAsCFF='false')] public static const font:Class; [Embed(source="/assets/segoeprb.ttf", fontName="Segoe", mimeType="application/x-font-truetype", fontWeight="bold", embedAsCFF='false')] public static const font2:Class; So, is there a way to get embedded fonts to work in design view or what?

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• d:DesignData issue, Visual Studio 2010 cant build after adding sample design data with Expression Bl

  - by Valko

  Hi, VS 2010 solution and Silverlight project builds fine, then: I open MyView.xaml view in Expression Blend 4 Add sample data from class (I use my class defined in the same project) after I add new sample design data with Expression blend 4, everything looks fine, you see the added sample data in the EB 4 fine, you also see the data in VS 2010 designer too. Close the EB 4, and next VS 2010 build is giving me this errors: Error 7 XAML Namespace http://schemas.microsoft.com/expression/blend/2008 is not resolved. C:\Code\source\...myview.xaml and: Error 12 Object reference not set to an instance of an object. ... TestSampleData.xaml when I open the TestSampleData.xaml I see that namespace for my class used to define sample data is not recognized. However this namespace and the class itself exist in the same project! If I remove the design data from the MyView.xaml: d:DataContext="{d:DesignData /SampleData/TestSampleData.xaml}" it builds fine and the namespace in TestSampleData.xaml is recognized this time?? and then if add: d:DataContext="{d:DesignData /SampleData/TestSampleData.xaml}" I again see in the VS 2010 designer sample data, but the next build fails and again I see studio cant find the namespace in my TestSampleData.xaml containing sample data. That cycle is driving me crazy. Am I missing something here, is it not possible to have your class defining sample design data in the same project you have the MyView.xaml view?? cheers Valko

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• passing java mail message object from between applications

  - by jezhilvalan

  I'm using java mail api 1.4.1 to obtain new emails. Two classes are being used to obtain emails and then parsing it. "GetMail" class communicates with mail server(Gmail,yahoo etc) and obtains the message object. Then the message object is passed to yet another class "MailFormatter" class, which then parses the message object, obtains the email headers (From,To,Subject etc) and then it parses the Multipart content to obtain the main body and attachments.Since both "Mail getting" and "Mail formatting" process are very resource intensive, these classes are going to be implemented as separate web applications.This application is going to monitor new emails for numerous email ids.If these ("GetMail" and "MailFormatter") are implemented as separate web applications, how can I pass the message object from "GetMail" app to "MailFormatter" app ? Is there a way through which I can persist the obtained message object in a certain location (a location which is common to both "GetMail" and "MailFormatter" applications), so that "GetMail" can persist the message object in that location, and then "MailFormatter" app can read "Message" objects from that location and carry out the parsing process. Message objects cannot be serialized. If they cannot be serialized how can I persist the state of java mail message object? please do help me to resolve this issue.

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• Design Decision - Scaling out web based application's architecture

  - by Vadi

  This question is about design decision. I am currently working on a web project that will have 40K users to start with and in couple of month expected to grow 50M users (not concurrent users though). I would like to have a architecture that can be scaled out easily without much effort. In order to explain, I would like to use a trivial scenario. Lets say, User entities and services such as CreateUser, AuthenticateUser etc., are a simple method calls for the Page Controllers. But once the traffic increases, for example, authenticating user (or such services related to user entities) has to be moved out to a different internal server to spread the load. But at the same time using RPC calls over the network when the user count is 40K would become overkill. My proposal was to use IPC initially and when we need to scale out we can interally switch to TCP based RPC calls so that it can easily scale out. For example, I am referring to System.IO.Pipes.NamedPipeStreamServer to start with and move on to a TcpListener later on. If we have proper design that can encapsulate above said approach, it would easy for us to scale out services into multiple network servers but at the same time avoid network calls when the user count is small. Is this is a best approach? Any suggestions would be great .. Note: The database scaling is definetly the second phase optimization so we have already made architectural design in place to easily partition data when traffic increases. The primary bottleneck would be application servers over the time period.

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• System.Design cannot be referenced in Class Library?

  - by Alex Yeung

  Hi all, I have a very strange problem that I cannot fix and don't know what's going on... I am using VS 2010 Premium and .NET 4.0. Here are my steps to simulate the problem. Step 1. Create a new VB class library project named "MyClassLib" Step 2. Create a new class named "MyTestingClass". Public Class MyTestingClass Inherits System.ComponentModel.Design.CollectionEditor Public Sub New() MyBase.New(GetType(List(Of String))) End Sub End Class Step 3. Add two .net reference. "System.Design" and "System.Drawing". Step 4. Create a new VB console application named "MyClassExe" Step 5. Add "MyClassLib" reference to "MyClassExe". Step 6. Open Module1.vb in "MyClassExe" project Step 7. In the Main method, type Dim a = New MyClassLib.MyTestingClass() Step 8. Try to compile "MyClassLib". It doesn't have problem. Step 9. Try to compile "MyClassExe". It cannot compile because the WHOLE MyClassLib cannot be found!!! I have no idea what's going on? Moreover, the same case happens in C#. Does anyone know what's the problem with "System.Design"? Thank!!!

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• Python access an object byref / Need tagging

  - by Aaron C. de Bruyn

  I need to suck data from stdin and create a object. The incoming data is between 5 and 10 lines long. Each line has a process number and either an IP address or a hash. For example: pid=123 ip=192.168.0.1 - some data pid=123 hash=ABCDEF0123 - more data hash=ABCDEF123 - More data ip=192.168.0.1 - even more data I need to put this data into a class like: class MyData(): pid = None hash = None ip = None lines = [] I need to be able to look up the object by IP, HASH, or PID. The tough part is that there are multiple streams of data intermixed coming from stdin. (There could be hundreds or thousands of processes writing data at the same time.) I have regular expressions pulling out the PID, IP, and HASH that I need, but how can I access the object by any of those values? My thought was to do something like this: myarray = {} for each line in sys.stdin.readlines(): if pid and ip: #If we can get a PID out of the line myarray[pid] = MyData().pid = pid #Create a new MyData object, assign the PID, and stick it in myarray accessible by PID. myarray[pid].ip = ip #Add the IP address to the new object myarray[pid].lines.append(data) #Append the data myarray[ip] = myarray[pid] #Take the object by PID and create a key from the IP. <snip>do something similar for pid and hash, hash and ip, etc...</snip> This gives my an array with two keys (a PID and an IP) and they both point to the same object. But on the next iteration of the loop, if I find (for example) an IP and HASH and do: myarray[hash] = myarray[ip] The following is False: myarray[hash] == myarray[ip] Hopefully that was clear. I hate to admit that waaay back in the VB days, I remember being able handle objects byref instead of byval. Is there something similar in Python? Or am I just approaching this wrong?

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• Receiving generic typed <T> custom objects through remote object in Flex

  - by Aaron

  Is it possible to receive custom generic typed objects through AMF? I'm trying to integrate a flex app with an existing C# service but flex is choking on custom generic typed objects. As far as I can tell Flex doesn't even support generics, but I'd like to be able to even just read in the object and cast its members as necessary. I basically just want flex to ignore the <T>. I'm hopeful that there's a way to do this, since flex doesn't complain about typed collections (a server call returning List works fine and flex converts it to an ArrayCollection just like an un-typed List). Here's a trimmed down example of what's going on for me: The custom C# typed class public class TypeTest<T> { public T value { get; set; } public TypeTest () { } } The server method returning the typeTest public TypeTest<String> doTypeTest() { TypeTest<String> theTester = new TypeTest<String>("grrrr"); return theTester; } The corresponding flex value object: [RemoteClass(alias="API.Model.TypeTest")] public class TypeTest { private var _value:Object; public function get value():Object { return _value; } public function set value(theValue:Object):void { _value = value; } public function TypeTest() { } } and the result handler code: public function doTypeTest(result:TypeTest):void { var theString:String = result.value as String; trace(theString); } When the result handler is called I get the runtime error: TypeError: Error #1034: Type Coercion failed: cannot convert mx.utils::ObjectProxy@11a98041 to com.model.vos.TypeTest. Irritatingly if I change the result handler to take parameter of type Object it works fine. Anyone know how to make this work with the value object? I feel like i'm missing something really obvious.

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• JPA native query join returns object but dereference throws class cast exception

  - by masato-san

  I'm using JPQL Native query to join table and query result is stored in List<Object[]>. public String getJoinJpqlNativeQuery() { String final SQL_JOIN = "SELECT v1.bitbit, v1.numnum, v1.someTime, t1.username, t1.anotherNum FROM MasatosanTest t1 JOIN MasatoView v1 ON v1.username = t1.username;" System.out.println("get join jpql native query is being called ============================"); EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getDefaultManager(); Query query = em.createNativeQuery(SQL_JOIN); out = query.getResultList(); System.out.println("return object ==========>" + out); System.out.println(out.get(0)); String one = out.get(0).toString(); //LINE 77 where ClassCastException System.out.println(one); } catch(Exception e) { } finally { if(em != null) { em.close; } } } The problem is System.out.println("return object ==========>" + out); outputs: return object ==========> [[true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020], [false, 0, 2010-12-21 15:32:53.0, koga, 0.213]] System.out.println(out.get(0)) outputs: [true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020] So I assumed that I can assign return value of out.get(0) which should be String: String one = out.get(0).toString(); But I get weird ClassCastException. java.lang.ClassCastException: java.util.Vector cannot be cast to [Ljava.lang.Object; at local.test.jaxrs.MasatosanTestResource.getJoinJpqlNativeQuery (MasatosanTestResource.java:77) So what's really going on? Even Object[] foo = out.get(0); would throw an ClassCastException :(

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• Calling into a saved java object via JNI from a different thread

  - by Drake Amara

  I have a java object which calls into a C++ shared object via JNI. In C++, I am saving a reference to the JNIEnv and jObject. JavaVM * jvm; JNIEnv * myEnv; jobject myobj; JNIEXPORT void JNICALL Java_org_api_init (JNIEnv *env, jobject jObj) { myEnv = env; myobj = jObj; } I also have a GLSurface renderer and it eventually calls the C++ shared object mentioned above on a different thread, the GLThread. I am then trying to call back into my original Java object using the jobject I saved initially, but I think because I am on the GLThread, I get the following error. W/dalvikvm(16101): JNI WARNING: 0x41ded218 is not a valid JNI reference I/dalvikvm(16101): "GLThread 981" prio=5 tid=15 RUNNABLE I/dalvikvm(16101): | group="main" sCount=0 dsCount=0 obj=0x41d6e220 self=0x5cb11078 I/dalvikvm(16101): | sysTid=16133 nice=0 sched=0/0 cgrp=apps handle=1555429136 I/dalvikvm(16101): | schedstat=( 0 0 0 ) utm=42 stm=32 core=1 The code calling back into Java : void setData() { jvm->AttachCurrentThread(&myEnv, 0); jclass javaClass = myEnv->FindClass("com/myapp/myClass"); if(javaClass == NULL){ LOGD("ERROR - cant find class"); } jmethodID method = myEnv->GetMethodID(javaClass, "updateDataModel", "()V"); if(method == NULL){ LOGD("ERROR - cant access method"); } // this works, but its a new java object //jobject myobj2 = myEnv->NewObject(javaClass, method); //this is where the crash occurs myEnv->CallVoidMethod(myobj, method, NULL); } If instead I create a new jObject using env-NewObject, I can succuessfully call back into Java, but it is a new object and I dont want that. I need to get back to my original Java Object. Is it a matter of switching threads before I call back into Java? If so, how do I do so ?

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• Javascript function objects, this keyword points to wrong object

  - by Rody van Sambeek

  I've got a problem concerning the javascript "this" keyword when used within a javascript functional object. I want to be able to create an object for handling a Modal popup (JQuery UI Dialog). The object is called CreateItemModal. Which i want to be able to instantiate and pass some config settings. One of the config settings. When the show method is called, the dialog will be shown, but the cancel button is not functioning because the this refers to the DOM object instead of the CreateItemModal object. How can I fix this, or is there a better approach to put seperate behaviour in seperate "classes" or "objects". I've tried several approaches, including passing the "this" object into the events, but this does not feel like a clean solution. See (simplified) code below: function CreateItemModal(config) { // initialize some variables including $wrapper }; CreateItemModal.prototype.show = function() { this.$wrapper.dialog({ buttons: { // this crashes because this is not the current object here Cancel: this.close } }); }; CreateItemModal.prototype.close = function() { this.config.$wrapper.dialog('close'); };

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• Javascript cloned object looses its prototype functions

  - by Jake M

  I am attempting to clone an object in Javascript. I have made my own 'class' that has prototype functions. My Problem: When I clone an object, the clone cant access/call any prototype functions. I get an error when I go to access a prototype function of the clone: clone.render is not a function Can you tell me how I can clone an object and keep its prototype functions This simple JSFiddle demonstrates the error I get: http://jsfiddle.net/VHEFb/1/ function cloneObject(obj) { // Handle the 3 simple types, and null or undefined if (null == obj || "object" != typeof obj) return obj; // Handle Date if (obj instanceof Date) { var copy = new Date(); copy.setTime(obj.getTime()); return copy; } // Handle Array if (obj instanceof Array) { var copy = []; for (var i = 0, len = obj.length; i < len; ++i) { copy[i] = cloneObject(obj[i]); } return copy; } // Handle Object if (obj instanceof Object) { var copy = {}; for (var attr in obj) { if (obj.hasOwnProperty(attr)) copy[attr] = cloneObject(obj[attr]); } return copy; } throw new Error("Unable to copy obj! Its type isn't supported."); } function MyObject(name) { this.name = name; // I have arrays stored in this object also so a simple cloneNode(true) call wont copy those // thus the need for the function cloneObject(); } MyObject.prototype.render = function() { alert("Render executing: "+this.name); } var base = new MyObject("base"); var clone = cloneObject(base); clone.name = "clone"; base.render(); clone.render(); // Error here: "clone.render is not a function"

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• Pass object or id

  - by Charles

  This is just a question about best practices. Imagine you have a method that takes one parameter. This parameter is the id of an object. Ideally, I would like to be able to pass either the object's id directly, or just the object itself. What is the most elegant way to do this? I came up with the following: def method_name object object_id = object.to_param.to_i ### do whatever needs to be done with that object_id end So, if the parameter already is an id, it just pretty much stays the same; if it's an object, it gets its id. This works, but I feel like this could be better. Also, to_param returns a string, which could in some cases return a "real" string (i.e. "string" instead of "2"), hence returning 0 upon calling to_i on it. This could happen, for example, when using the friendly id gem for classes. Active record offers the same functionality. It doesn't matter if you say: Table.where(user_id: User.first.id) # pass in id or Table.where(user_id: User.first) # pass in object and infer id How do they do it? What is the best approach to achieve this effect?

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• WPF Databinding With A Collection Object

  - by Randster

  Argh, although I've been googling, I really would appreciate it if someone could break my problem down as all the code examples online are confusing me more than assisting (perhaps it's just late)... I have a simple class as defined below: public class Person { int _id; string _name; public Person() { } public int ID { get { return _id; } set { _id = value; } } public string Name { get { return _name; } set { _name = value; } } } that is stored in a database, and thru a bit more code I put it into an ObservableCollection object to attempt to databind in WPF later on: public class People : ObservableCollection<Person> { public People() : base() { } public void Add(List<Person> pListOfPeople) { foreach (Person p in pListOfPeople) this.Add(p); } } In XAML, I have myself a ListView that I would like to populate a ListViewItem (consisting of a textblock) for each item in the "People" object as it gets updated from the database. I would also like that textblock to bind to the "Name" property of the Person object. I thought at first that I could do this: lstPeople.DataContext = objPeople; where lstPeople is my ListView control in my XAML, but that of course does nothing. I've found TONS of examples online where people through XAML create an object and then bind to it through their XAML; but not one where we bind to an instantiated object and re-draw accordingly. Could someone please give me a few pointers on: A) How to bind a ListView control to my instantiated "People" collection object? B) How might I apply a template to my ListView to format it for the objects in the collection? Even links to a decent example (not one operating on an object declared in XAML please) would be appreciated. Thanks for your time.

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• Repeating fields in similar database tables

  - by user1738833

  I have been tasked with working on a database that I have never seen before and I'm looking at the DB structure. Some of the central and most heavily queried and joined tables look like virtual duplicates of each other. Here's a massively simplified representation of the situation, with business-sensitive information changed, listing hypothetical table names and fields: TopLevelGroup: PK_TLGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubGroup: PK_SubGroupId, FK_ParentTopLevelGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubSubGroup: PK_SubSUbGroupId, FK_ParentSubGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK I haven't listed the types of the fields as I don't think it's particularly important to the situation. In addition, it's worth saying that rather than four repeated fields as in the example above, I'm looking at 86 repeated fields. For the most part, those fields genuinely do represent "facts" about the primary table entity, so it's not automatically wrong for that reason. In addition, the "groups" represented here have a property inheritance relationship. If DisplaysXOnBill is NULL in the SubSubGroup, it takes the value of DisplaysXOnBillfrom it's parent, the SubGroup, and so-on up to the TopLevelGroup. Further, the requirements will never require that the model extends beyond three levels, so there is no need for flexibility in that area. Is there a design smell from several tables which describe very similar entities having almost identical fields? If so, what might be a better design of the example above? I'm using the phrase "design smell" to indicate a possible problem. Of course, in any given situation, a particular design might well be the best solution. I'm looking for a more general answer - wondering what might be wrong with this design and what might be the better design were that the case. Possibly related, but not primary questions: Is this database schema in a reasonably normal form (e.g. to 3NF), insofar as can be told from the information I've provided. I can't see a problem with the requirements of 2NF and 3NF, except in their inheriting the requirements of 1NF. Is 1NF satisfied though? Are repeating groups allowed in different tables? Is there a best-practice method for implementing the inheritance relationship in a database as I require? The method above feels clunky to me because any query on the SubSubGroup necessarily needs to join onto the SubGroup and the TopLevelGroup tables to collect inherited facts, which can make even trivial joins requiring facts from the SubSubGroup table rather long-winded. There are, of course, political considerations to making a relatively large change like this. For the purpose of this question, I'm happy to ignore that fact in the interests of keeping the answers ring-fenced to the technical problem.

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• Is deriving square from rectangle a violation of Liskov's Substitution Principle?

  - by somaraj

  I am new to design and learning the design principles. It says deriving square from rectangle is a classic example of violation of Liskov's Substitution Principle. If that's the case, what should be the correct design?

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• Apache2 server does not start cannot pen shared object file

  - by sid__

  I am working with Apache and Passenger for a Rails project. And a during a restart I got the following error Cannot load /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so into server: /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so: cannot open shared object file: No such file or directory However there is no change in the apache configuration file. I have attached the snippet from the conf file 287 LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so 288 PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11 289 PassengerRuby /usr/bin/ruby1.8 I am also unable to locate the shared object file in the location pointed to by the server though I am not really sure how the .so file is works (created/destroyed) I would also appreciate it if someone could explain to me what exactly has happened. I understand the shared object file is mission, what could be the reason it got deleted.

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• Partial Trust in WPF 4

  - by Hadi Eskandari

  I've started a new project in WPF 4 (.NET 4) and trying to see if I can run it in xbap mode. I need to run the application in Full Trust with the new mode made available in .NET 4 which asks the end user if the full trust application should be run. I've set the "Security" mode to "Full Trust" application, and it builds just fine. When I run it, an exception is thrown and IE error message shows the following error. Any ways around it?? Startup URI: T:\projects\Hightech Sources\PayRoll\PayRoll.Web\publish\PayRoll.Web.xbap Application Identity: file:///T:/projects/Hightech%20Sources/PayRoll/PayRoll.Web/publish/PayRoll.Web.xbap#PayRoll.Web.xbap, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1d910f49755d2c97, processorArchitecture=msil/PayRoll.Web.exe, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1d910f49755d2c97, processorArchitecture=msil, type=win32 System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessSecurityEngine.Check(CodeAccessPermission cap, StackCrawlMark& stackMark) at System.Security.CodeAccessPermission.Demand() at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection, Boolean suppressSecurityChecks) at System.Reflection.RuntimeAssembly.InternalLoadFrom(String assemblyFile, Evidence securityEvidence, Byte[] hashValue, AssemblyHashAlgorithm hashAlgorithm, Boolean forIntrospection, Boolean suppressSecurityChecks, StackCrawlMark& stackMark) at System.Reflection.Assembly.LoadFrom(String assemblyFile) at PayRoll.Web.App.SelectAssemblies() at Caliburn.PresentationFramework.ApplicationModel.CaliburnApplication..ctor() at PayRoll.Web.App..ctor() at PayRoll.Web.App.Main() at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel) at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData) at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext) at System.Windows.Interop.PresentationApplicationActivator.CreateInstance(ActivationContext actCtx) at System.Activator.CreateInstance(ActivationContext activationContext) at System.AppDomain.Setup(Object arg) at System.AppDomain.nCreateInstance(String friendlyName, AppDomainSetup setup, Evidence providedSecurityInfo, Evidence creatorsSecurityInfo, IntPtr parentSecurityDescriptor) at System.Runtime.Hosting.ApplicationActivator.CreateInstanceHelper(AppDomainSetup adSetup) at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData) at System.Windows.Interop.PresentationApplicationActivator.CreateInstance(ActivationContext actCtx) at System.Activator.CreateInstance(ActivationContext activationContext) at System.Deployment.Application.DeploymentManager.ExecuteNewDomain() at System.Deployment.Application.InPlaceHostingManager.Execute() at MS.Internal.AppModel.XappLauncherApp.ExecuteDownloadedApplication() at System.Windows.Interop.DocObjHost.RunApplication(ApplicationRunner runner) at MS.Internal.AppModel.XappLauncherApp.XappLauncherApp_Exit(Object sender, ExitEventArgs e) at System.Windows.Application.OnExit(ExitEventArgs e) at System.Windows.Application.DoShutdown() at System.Windows.Application.ShutdownImpl() at System.Windows.Application.ShutdownCallback(Object arg) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.StartDispatcherInBrowser(Object unused) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.FileIOPermission

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• NHibernate IUserType convert nullable DateTime to DB not-null value

  - by barakbbn

  I have legacy DB that store dates that means no-date as 9999-21-31, The column Till_Date is of type DateTime not-null="true". in the application i want to build persisted class that represent no-date as null, So i used nullable DateTime in C# //public DateTime? TillDate {get; set; } I created IUserType that knows to convert the entity null value to DB 9999-12-31 but it seems that NHibernate doesn't call SafeNullGet, SafeNullSet on my IUserType when the entity value is null, and report a null is used for not-null column. I tried to by-pass it by mapping the column as not-null="false" (changed only the mapping file, not the DB) but it still didn't help, only now it tries to insert the null value to the DB and get ADOException. Any knowledge if NHibernate doesn't support IUseType that convert null to not-null values? Thanks //Implementation public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = rs.GetDateTime(rs.GetOrdinal(names[0])); return (value == MaxDate)? null : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; ((IDataParameter)cmd.Parameters[index]).Value = dbValue; } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } } //Final Implementation with fixes. make the column mapping in hbm.xml not-null="false" public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = NHibernateUtil.Date.NullSafeGet(rs, names[0]); return (value == MaxDate)? default(DateTime?) : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; NHibernateUtil.Date.NullSafeSet(cmd, valueToSet, index); } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } }

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• General advice and guidelines on how to properly override object.GetHashCode()

  - by Svish

  According to MSDN, a hash function must have the following properties: If two objects compare as equal, the GetHashCode method for each object must return the same value. However, if two objects do not compare as equal, the GetHashCode methods for the two object do not have to return different values. The GetHashCode method for an object must consistently return the same hash code as long as there is no modification to the object state that determines the return value of the object's Equals method. Note that this is true only for the current execution of an application, and that a different hash code can be returned if the application is run again. For the best performance, a hash function must generate a random distribution for all input. I keep finding myself in the following scenario: I have created a class, implemented IEquatable<T> and overridden object.Equals(object). MSDN states that: Types that override Equals must also override GetHashCode ; otherwise, Hashtable might not work correctly. And then it usually stops up a bit for me. Because, how do you properly override object.GetHashCode()? Never really know where to start, and it seems to be a lot of pitfalls. Here at StackOverflow, there are quite a few questions related to GetHashCode overriding, but most of them seems to be on quite particular cases and specific issues. So, therefore I would like to get a good compilation here. An overview with general advice and guidelines. What to do, what not to do, common pitfalls, where to start, etc. I would like it to be especially directed at C#, but I would think it will work kind of the same way for other .NET languages as well(?). I think maybe the best way is to create one answer per topic with a quick and short answer first (close to one-liner if at all possible), then maybe some more information and end with related questions, discussions, blog posts, etc., if there are any. I can then create one post as the accepted answer (to get it on top) with just a "table of contents". Try to keep it short and concise. And don't just link to other questions and blog posts. Try to take the essence of them and then rather link to source (especially since the source could disappear. Also, please try to edit and improve answers instead of created lots of very similar ones. I am not a very good technical writer, but I will at least try to format answers so they look alike, create the table of contents, etc. I will also try to search up some of the related questions here at SO that answers parts of these and maybe pull out the essence of the ones I can manage. But since I am not very stable on this topic, I will try to stay away for the most part :p

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• Embedded Office Application - How to know whether the app is running or the object is embedded

  - by A9S6

  I am adding an Excel Worksheet object inside Word. Excel has a COM addin attached to it. Any idea how one can know whether Excel is running independently or as an embedded object? The COM Addin attached to Excel loads when the embedded Excel object is activated (double-clicked) inside Word. I am looking for some kind of a property or a parameter in OnConnection(...) or other method that can tell the state of Excel object.

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