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• Password hashing, salt and storage of hashed values

  - by Jonathan Leffler

  Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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• problem when cloning jQuery UI datepicker

  - by h3

  I have a div in which there is a datepicker. I use something like this to clone it: mydiv = $('#someDiv'); // works fine so far mydiv.find('input.datefield').datepicker(); // clone without the events and insert newDiv = myDiv.clone(false).insertAfter(myDiv); // datepicker won't re-init if this class is present newDiv.find('.hadDatepicker').removeClass('hadDatepicker'); // reinitialize datepicker newDiv.find('input.datefield').datepicker(); This is a stripped down version of my code. It works and the calendar shows up as expected where it is expected .. but when a date is clicked, the previous datepicker's value gets updated.. (the one from which it was cloned). I've tried to destroy the (inexisting) instance before like this: newDiv.find('input.datefield').datepicker('destroy').datepicker(); No luck .. I've checked how it keeps track of instances and manually cleared the data like this: newDiv.find('input.datefield').data('datepicker', false).datepicker('destroy').datepicker(); Still no luck. What I don't understand is that only the date selection behavior is buggy, everything else works as expected. I really don't know what else to check now ..

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• window.setInterval from inside an object

  - by Keith Rousseau

  I'm currently having an issue where I have a javascript object that is trying to use setInterval to call a private function inside of itself. However, it can't find the object when I try to call it. I have a feeling that it's because window.setInterval is trying to call into the object from outside but doesn't have a reference to the object. FWIW - I can't get it to work with the function being public either. The basic requirement is that I may need to have multiple instances of this object to track multiple uploads that are occurring at once. If you have a better design than the current one or can get the current one working then I'm all ears. The following code is meant to continuously ping a web service to get the status of my file upload: var FileUploader = function(uploadKey) { var intervalId; var UpdateProgress = function() { $.get('someWebService', {}, function(json) { alert('success'); }); }; return { BeginTrackProgress: function() { intervalId = window.setInterval('UpdateProgress()', 1500); }, EndTrackProgress: function() { clearInterval(intervalId); } }; }; This is how it is being called: var fileUploader = new FileUploader('myFileKey'); fileUploader.BeginTrackProgress();

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• iPhone: Leak with UIWebView loading Office documents. Any ideas how to avoid it?

  - by Thomas Tempelmann

  While there are already quite a few posts about leaks around UIWebView, mine is a bit more special, I believe, and thus deserves its own post here. I see a reproducible large leak every time I load a Office document such as a Word or Excel file. For instance, every time I display a 180KB .doc file, I get a 100KB leak. And that happens with both the simulator and an actual device, running OS 3.1.3. The leak is not visible with the Leaks instrument but only by looking at the malloc instances via the ObjectAlloc instrument. Here's a picture from the instruments trace: I've also made a demo project, UIWebView-Leak.zip, so you can verify this yourself. To see the leak, use the ObjectAlloc instrument, switch to the view where you see individual allocation objects, and sort by size so that you see the large ones in a group, just like in my picture above. Then view a Office document a few times and find the Malloc objects that keep staying "Live" even after the actual UIWebView has been freed. Is this a known bug? Or is there any way I can avoid these leaks? I.e, have you successfully shown Office documents on an iPhone withing getting such leaks? Note: I've reported this as a bug to Apple now, too (ID 7950594) I am still waiting for someone (including Apple) to confirm this as a true leak or show why it isn't (i.e. that I do something wrong or make wrong assumptions)

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• Complicated SQL query

  - by Yandawl

  Please bare with me this is difficult to explain xD http://img90.imageshack.us/i/croppercapture1.png/ This is based on an undergraduate degree course where a student takes many units (say 4 core units and 1 optional unit per year). tblAwardCoreUnits and tblAwardOptUnits store which units are optional and core for which award, hence the relationship to tblAward and tblStudentCoreUnits and tblStudentOptUnits store the particular instances of those units which a particular student is taking. Secondly, a unit can have multiple events (say a lecture and a unit) and each of those events has sessions in which a student can attend, hence tblEvents, tblSessions and tblAttendances. The query I am trying to produce is to get a list of all level one students, grouped by their award that lists the percentage of attendances in all the units in the current level. I've tried and tried with this and the following is the best I've managed to come up with so far... I'd REALLY appreciate any help you can give with this! SELECT tblStudents.enrolmentNo, tblStudents.forename, tblStudents.surname, tblAwards.title, (SELECT COUNT((tblAttendances.attended + tblAttendances.authorisedAbsence)) AS SumOfAttendances FROM tblAttendances INNER JOIN (tblStudents ON tblStudents.enrolmentNo = tblAttendances.enrolmentNo)) / FROM tblUnits, tblAwards INNER JOIN ((tblStudents INNER JOIN tblStudentOptUnit ON tblStudents.studentID = tblStudentOptUnit.studentID) INNER JOIN tblStudentCoreUnit ON tblStudents.studentID = tblStudentCoreUnit.studentID) ON tblAwards.awardID = tblStudents.awardID WHERE (((tblStudents.level)="1") AND ((tblStudents.status)="enrolled")) GROUP BY tblAwards.title ORDER BY tblStudents.forname;

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• Is there a way to automaticly call all versions of an inherited method?

  - by Eric

  I'm writing a plug-in for a 3D modeling program. I have a custom class that wraps instances of elements in the 3D model, and in turn derives it's properties from the element it wraps. When the element in the model changes I want my class(es) to update their properties based on the new geometry. In the simplified example below. I have classes AbsCurveBasd, Extrusion, and Shell which are all derived from one another. Each of these classes implement a RefreshFromBaseShape() method which updates specific properties based on the current baseShape the class is wrapping. I can call base.RefreshFromBaseShape() in each implementation of RefreshFromBaseShape() to ensure that all the properties are updated. But I'm wondering if there is a better way where I don't have to remember to do this in every implementation of RefershFromBaseShape()? For example because AbsCurveBased does not have a parameterless constructor the code wont even compile unless the constructors call the base class constructors. public abstract class AbsCurveBased { internal Curve baseShape; double Area{get;set;} public AbsCurveBased(Curve baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public virtual void RefreshFromBaseShape() { //sets the Area property from the baseShape } } public class Extrusion : AbsCurveBased { double Volume{get;set;} double Height{get;set;} public Extrusion(Curve baseShape):base(baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public override void RefreshFromBaseShape() { base.RefreshFromBaseShape(); //sets the Volume property based on the area and the height } } public class Shell : Extrusion { double ShellVolume{get;set;} double ShellThickness{get;set;} public Shell(Curve baseShape): base(baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public void RefreshFromBaseShape() { base.RefreshFromBaseShape(); //sets this Shell Volume from the Extrusion properties and ShellThickness property } }

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• Which source control paradigm and solution to embed in a custom editor application?

  - by Greg Harman

  I am building an application that manages a number of custom objects, which may be edited concurrently by multiple users (using different instances of the application). These objects have an underlying serialized representation, and my plan is to persist them (through my application UI) in an external source control system. Of course this implies that my application can check the current version of an object for updates, a merging interface for each object, etc. My question is what source control paradigm(s) and specific solution(s) to support and why. The way I (perhaps naively) see the source control world is three general paradigms: Single-repository, locked access (MS SourceSafe) Single-repository, concurrent access (CVS/SVN) Distributed (Mercurial, Git) I haven't heard of anyone using #1 for quite a number of years, so I am planning to disregard this case altogether (unless I get a compelling argument otherwise). However, I'm at a loss as to whether to support #2 or #3, and which specific implementations. I'm concerned that the use paradigms are subtly different enough that I can't adequately capture basic operations in a single UI. The last bit of information I should convey is that this application is intended to be deployed in a commercial setting, where a source control system may already be in use. I would prefer not to support more than one solution unless it's really a deal-breaker, so wide adoption in a corporate setting is a plus.

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• Using data binding on value which is a FrameworkElement

  - by JaredPar

  One of my data sources produces a collection of values which are typed to the following interface public interface IData { string Name { get; } FrameworkElement VisualElement { get; } } I'd like to use data binding in WPF to display a collection of IData instances in a TabControl where the Name value becomes the header of the tab and the VisualElement value is displayed as the content of the corresponding tab. Binding the header is straight forward. I'm stuck though on how to define a template which allows me to display the VisualElement value. I've tried a number of solutions with little success. My best attempt is as follows. <TabControl ItemsSource="{Binding}"> <TabControl.ItemTemplate> <DataTemplate> <Label Content="{Binding Name}"/> </DataTemplate> </TabControl.ItemTemplate> <TabControl.ContentTemplate> <DataTemplate> How do I display VisualElement here? </DataTemplate> </TabControl.ContentTemplate> </TabControl> I'm still very new to WPF so I could be missing the obvious here.

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• Improving field get and set performance with ASM

  - by ng

  I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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• How can I make a family of singletons?

  - by Jay

  I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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• Tips on designing a .NET API for future use with F#

  - by Drew Noakes

  I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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• WPF - List items not visible in Blend when 'DisplayMemberPath' is used

  - by Andy T

  Hi, We're currently working out how to implement MVVM and I've got to the point where I've got the MVVM Light Toolkit set up in blend and can specify dummy data to be supplied if running in Blend. All good. I've created a dummy list of data. The list contains 6 instances of a very simple class called DummyItem which has Age and Name properties. Here's the main code from my 'DummyList' class: public class DummyItem{ public string Name; public int Age; public DummyItem(string name, int age){ this.Name = name; this.Age = age; } } public class DummyList : ArrayList { public DummyList() { this.Add(new DummyItem("Dummy1", 00)); this.Add(new DummyItem("Dummy2", 01)); this.Add(new DummyItem("Dummy3", 02)); this.Add(new DummyItem("Dummy4", 03)); this.Add(new DummyItem("Dummy5", 04)); this.Add(new DummyItem("Dummy6", 05)); } } Here's the operative part of my XAML. The DataContext line does work and points to the correct ViewModel. <Grid x:Name="LayoutRoot"> <ListBox x:Name="ListViewBox" DataContext="{Binding Source={StaticResource Locator}, Path=ListViewModel}" ItemsSource="{Binding TheList}" DisplayMemberPath="Name"> </ListBox> </Grid> The problem is, when I add 'DisplayMemberPath', as I have above, then I can no longer see the list items in Blend. If I remove 'DisplayMemberPath', then I see a list of objects (DummyItem) with their full path. When the app is run, everything works perfectly. It's just that in Blend itself I cannot see the list items when I use 'DisplayMemberPath'. Anyone know why I can't see the items inside Blend itself when I use DisplayMemberPath? Thanks! AT

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• Bulk insert of component collection in Hibernate?

  - by edbras

  I have the mapping as listed below. When I update a detached Categories item (that doesn't contain any Hibernate class as it comes from a dto converter) I notice that Hibernate will first delete ALL employer wages instances (the collection link) and then insert ALL employer wage entries ONE-BY-ONE :(... I understand that it has to delete and then insert all entries as it was completely detached. BUT, what I don't understand, why is Hibernate NOT inserting all the entries through bulk-insert?.. That is: inserting all the employer wage entries all in one SQL statement ? How can I tell Hibernate to use bulk-insert? (if possible). I tried playing with the following value but didn't see any difference: hibernate.jdbc.batch_size=30 My mapping snippet: <class name="com.sample.CategoriesDefault" table="dec_cats" > <id name="id" column="id" type="string" length="40" access="property"> <generator class="assigned" /> </id> <component name="incomeInfoMember" class="com.sample.IncomeInfoDefault"> <property name="hasWage" type="boolean" column="inMemWage"/> ... <component name="wage" class="com.sample.impl.WageDefault"> <property name="hasEmployerWage" type="boolean" column="inMemEmpWage"/> ... <set name="employerWages" cascade="all-delete-orphan" lazy="false"> <key column="idCats" not-null="true" /> <one-to-many entity-name="mIWaEmp"/> </set> </component> </component> </class>

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• Left/Right/Inner joins using C# and LINQ

  - by Keith Barrows

  I am trying to figure out how to do a series of queries to get the updates, deletes and inserts segregated into their own calls. I have 2 tables, one in each of 2 databases. One is a Read Only feeds database and the other is the T-SQL R/W Production source. There are a few key columns in common between the two. What I am doing to setup is this: List<model.AutoWithImage> feedProductList = _dbFeed.AutoWithImage.Where(a => a.ClientID == ClientID).ToList(); List<model.vwCompanyDetails> companyDetailList = _dbRiv.vwCompanyDetails.Where(a => a.ClientID == ClientID).ToList(); foreach (model.vwCompanyDetails companyDetail in companyDetailList) { List<model.Product> productList = _dbRiv.Product.Include("Company").Where(a => a.Company.CompanyId == companyDetail.CompanyId).ToList(); } Now that I have a (source) list of products from the feed, and an existing (target) list of products from my prod DB I'd like to do 3 things: Find all SKUs in the feed that are not in the target Find all SKUs that are in both, that are active feed products and update the target Find all SKUs that are in both, that are inactive and soft delete from the target What are the best practices for doing this without running a double loop? Would prefer a LINQ 4 Objects solution as I already have my objects. EDIT: BTW, I will need to transfer info from feed rows to target rows in the first 2 instances, just set a flag in the last instance. TIA

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• Ideas on frameworks in .NET that can be used for job processing and notifications

  - by Rajat Mehta

  Scenario: We have one instance of WCF windows service which exposes contracts like: AddNewJob(Job job), GetJobs(JobQuery query) etc. This service is consumed by 70-100 instances of client which is Windows Form based .NET app. Typically the service has 50-100 inward calls/minute to add or query jobs that are stored in a table on Sql Server. The same service is also responsible for processing these jobs in real time. It queries database every 5 seconds picks up the queued jobs and starts processing them. A job has 6 states. Queued, Pre-processing, Processing, Post-processing, Completed, Failed, Locked. Another responsibility on this service is to update all clients on every state change of every job. This means almost 200+ callbacks to clients per second. Question: This whole implementation is done using WCF Duplex bindings and works perfectly fine on small number of parallel jobs. Problem arises when we scale it up to 1000 jobs at a time. The notifications don't work as expected, it leads to memory overflow etc. Is there any standard framework that can provide a clean infrastructure for handling this scenario?? Apologies for the long explanation!

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• SSIS Transaction with Sql Transaction

  - by Mike

  I started with a package to make sure Transactions are working correctly. The package level transaction is set to Required. I have two Execute Sql Task, one deletes rows from a table and one does 1/0, to throw the error. Both task are set to supported transaction level and Serializable IsolationLevel. That works. Now when I replace my two sql task to two separate procedure calls, the first one, ChargeInterest, runs successful but the second one, PaymentProcess, fails always saying. [Execute SQL Task] Error: Executing the query "Exec [proc_xx_NotesReceivable_PaymentProcess] ..." failed with the following error: "Uncommittable transaction is detected at the end of the batch. The transaction is rolled back.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly. PaymentProcess being the second stored procedure. Both procedures have there own BEGIN, COMMIT AND ROLLBACKS inside the SP. I believe that the transactions are being successfully handed in the Charge Interest because I can run the following without issues or the dreaded you started with 0 and now have 1 transaction. EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 --OR GO BEGIN TRAN EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 ROLLBACK TRAN Now I have noticed that DTC does get kicked off in both instances? Why I am not sure because it is using the same connection. In the live example I can see the transaction get started but disappears if I put a breakpoint on the PreExecute event of the second stored procedure. What is the correct way to mingle SP transactions with SSIS transactions?

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• Working with extra fields in an Inline form - save_model, save_formset, can't make sense of the diff

  - by magicrebirth

  Suppose I am in the usual situation where there're extra fields in the many2many relationship: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) # other models which are unrelated to the ones above.. class Trip(models.Model): placeVisited = models.ForeignKey(Place) visitor = models.ForeignKey(Person) pleasuretrip = models.Boolean() class Place(models.Model): name = models.CharField(max_length=128) I want to add some extra fields in the Membership form that gets displayed through the Inline. These fields basically are a shortcut to the instantiation of another model (Trip). Trip can have its own admin views, but these shortcuts are needed because when my project partners are entering 'Membership' data in the system they happen to have also the 'Trip' information handy (and also because some of the info in Membership can just be copied over to Trip etc. etc.). So all I want to have is two extra fields in the Membership Inline - placeVisited and pleasuretrip - which together with the Person instance will let me instantiate the Trip model in the background... I found out I can easily add extra fields to the inline view by defining my own form. But once the data have been entered, how and when to reference to them in order to perform the save operations I need to do? class MyForm(forms.ModelForm): place = forms.ModelChoiceField(required=False, queryset=Place.objects.all(), label="place",) pleasuretrip = forms.BooleanField(required=False, label="...") class MembershipInline(admin.TabularInline): model = Membership form = MyForm def save_model(self, request, obj, form, change): place = form.place pleasuretrip = form.pleasuretrip person = form.person .... # now I can create Trip instances with those data .... obj.save() class GroupAdmin(admin.ModelAdmin): model = Group .... inlines = (MembershipInline,) This doesn't seem to work... I'm also a bit puzzled by the save_formset method... maybe is that the one I should be using? Many thanks in advance for the help!!!!

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• Alternative way of implementation of a code

  - by vikramjb

  The title is not exactly meaningful, but I am not share what else to name it. I wrote a TOC Generation code sometime later. Based on this I was writing code to check for duplicates also. The code is as follows curNumber = getTOCReference(selItem.SNo, IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); curNumber = realTOCRef; And the code for CheckForDuplicates is ListViewItem curItem = this.tlvItems.FindItemWithText(curNumber); if (curItem != null) { curNumber = this.getTOCReference(curNumber, !IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); } else { realTOCRef= curNumber; } What this code does, it gets a TOC and tries it find if it already exists in the ObjectListView and gets a new TOC if there is a existing TOC. Once it determines that the generated TOC is not there in the list it stores it in realTOCRef and sends it back to the main calling code. I have used "out" to return the last generated TOC, which is something I did not want to do. The reason why I did it was after the non duplicate TOC was generated the return was not going back to the calling code instead it looped through the previous instances then it returned back. When the looping back happened the TOC that was to be returned also got reset. I would appreciate any help on this.

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• Why does Microsoft advise against readonly fields with mutable values?

  - by Weeble

  In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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• RSKeyMgmt -r unable to remove installtion ID

  - by Eves

  I have backed up databases on one 2005 SQL Server and have restored those databases on a second 2005 SQL Server. I am currently trying to remove the new server's OLD key instance ID using the Reporting Services Key Manager (RSKeyMgmt -r). Prior to running the removal command the list of the current instances shows the new server's OLD instance ID as well as the NEW instance ID from the first SQL Server. Executing the RSKeyMgmt -r command results in: "The command completed successfully". However, when I recheck the listing of current instance IDs I see both the OLD and NEW instance IDs. In addition, when I check the Application Event Viewer I see an error: Report Server Windows Service (MSSQLSERVER) has not been granted access to the catalog content Does anyone know why I would be getting the above application error? Or...does anyone know what I would need to do to give access to the catalog to the Report Server Window Service? The first SQL Server where the databases were backed up is an Enterprise edition SQL Server and the second SQL Server where the databases were restored is Standard edition. Could this be the cause of the problem? Is there a way to make this backup and restore migration work?

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• What setting needs to be made to make .Net Automation responsive?

  - by Greg

  Have an app that is looking for application windows being created on the desktop using class Unresponsive { private StructureChangedEventHandler m_UIAeventHandler = new StructureChangedEventHandler(OnStructureChanged); public Unresponsive() { Automation.AddStructureChangedEventHandler(AutomationElement.RootElement, TreeScope.Children, m_UIAeventHandler); } private void OnStructureChanged(object sender, StructureChangedEventArgs e) { Debug.WriteLine("Change event"); } } You can see the same issue using UISpy.exe, selecting the desktop and configuring scope for children and just the structure changed event. The problem I'm trying to resolve is that the events are not raised in a timely manner, there seems to be some grouping/delay which makes the app appear to be non responsive. If you start a new app with 1 window and wait a second you get the event, seems alright. If you start the same app several times without delay (say clicking on quickstart), it's not until all of the instances of the app get 'initialised' by the AutomationProxies that you get the notice for the first app (and in short order the other apps/windows). I've sat watching task manager as each instance of the app starts to grow as it is initialised, waiting until the last app is done and then seeing the events all come in. Similarly any time any apps are starting windows within a timeframe there seems to be some blocking. I can't see how to configure this timeframe, or get each structure changed event to be sent on as soon as it happens. Also, this process of listening for structure changed events seems to be leaking, just by listening there is a leak in native memory. (visible in UISpy and my app)

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• MySql Query lag time?

  - by Click Upvote

  When there are multiple PHP scripts running in parallel, each making an UPDATE query to the same record in the same table repeatedly, is it possible for there to be a 'lag time' before the table is updated with each query? I have basically 5-6 instances of a PHP script running in parallel, having been launched via cron. Each script gets all the records in the items table, and then loops through them and processes them. However, to avoid processing the same item more than once, I store the id of the last item being processed in a seperate table. So this is how my code works: function getCurrentItem() { $sql = "SELECT currentItemId from settings"; $result = $this->db->query($sql); return $result->get('currentItemId'); } function setCurrentItem($id) { $sql = "UPDATE settings SET currentItemId='$id'"; $this->db->query($sql); } $currentItem = $this->getCurrentItem(); $sql = "SELECT * FROM items WHERE status='pending' AND id > $currentItem'"; $result = $this->db->query($sql); $items = $result->getAll(); foreach ($items as $i) { //Check if $i has been processed by a different instance of the script, and if so, //leave it untouched. if ($this->getCurrentItem() > $i->id) continue; $this->setCurrentItem($i->id); // Process the item here } But despite of all the precautions, most items are being processed more than once. Which makes me think that there is some lag time between the update queries being run by the PHP script, and when the database actually updates the record. Is it true? And if so, what other mechanism should I use to ensure that the PHP scripts always get only the latest currentItemId even when there are multiple scripts running in parrallel? Would using a text file instead of the db help?

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• C# how to calculate hashcode from an object reference.

  - by Wayne

  Folks, here's a thorny problem for you! A part of the TickZoom system must collect instances of every type of object into a Dictionary< type. It is imperative that their equality and hash code be based on the instance of the object which means reference equality instead of value equality. The challenge is that some of the objects in the system have overridden Equals() and GetHashCode() for use as value equality and their internal values will change over time. That means that their Equals and GetHashCode are useless. How to solve this generically rather than intrusively? So far, We created a struct to wrap each object called ObjectHandle for hashing into the Dictionary. As you see below we implemented Equals() but the problem of how to calculate a hash code remains. public struct ObjectHandle : IEquatable<ObjectHandle>{ public object Object; public bool Equals(ObjectHandle other) { return object.ReferenceEquals(this.Object,other.Object); } } See? There is the method object.ReferenceEquals() which will compare reference equality without regard for any overridden Equals() implementation in the object. Now, how to calculate a matching GetHashCode() by only considering the reference without concern for any overridden GetHashCode() method? Ahh, I hope this give you an interesting puzzle. We're stuck over here. Sincerely, Wayne

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• MySql: Query multiple identical dynamic tables.

  - by JYelton

  I have a database with 500+ tables, each with identical structure, that contain historical data from sensors. I am trying to come up with a query that will locate, for example, all instances where sensor n exceeds x. The problem is that the tables are dynamic, the query must be able to dynamically obtain the list of tables. I can query information_schema.tables to get a list of the tables, like so: SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name'; I can use this to create a loop in the program and then query the database repeatedly, however it seems like there should be a way to have MySql do the multiple table search. I have not been able to make a stored procedure that works, but the examples I can find are generally for searching for a string in any column. I want to specifically find data in a specific column that exists in all tables. I admit I do not understand how to properly use stored procedures nor if they are the appropriate solution to this problem. An example query inside the loop would be: SELECT device_name, sensor_value FROM device_table WHERE sensor_value > 10; Trying the following does not work: SELECT device_name, sensor_value FROM ( SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name' ) WHERE sensor_value > 10; It results in an error: "Every derived table must have its own alias." The goal is to have a list of all devices that have had a given sensor value occur anywhere in their log (table). Ultimately, should I just loop in my program once I've obtained a list of tables, or is there a query structure that would be more efficient?

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• xPath Groupings how?

  - by David

  OK So, I'm learning/using xpath for a basic application thats effectively ripping data off another website. I need to gain the knowledge of each persons Countryy/Suburb/area. In some instances you can get Australia/Victoria/melborne for instance. Others may just be Australia/Melbourne. Or even just Melbourne OR just AUSTRALIA. who knows. So I'm current able to view the below code and rip all of the information with the string xpath search:@" //table/tr/td/tabke/tr/td/font/a, this returns every entry, but what I really want is to group each lot separately. I hope someone out there on planet earth knows what I just tried to explain... and can help... Good day! <font face="arial" size="2"> <strong>Location:</strong> <a href="http://maps.google.com/maps?q=Australia" target="mapblast" style="text-decoration:none">Australia</a>, <a href='http://maps.google.com/maps?q=Australia%20Victoria'target="mapblast" style='text-decoration:none'>Victoria</a>, <a href='http://maps.google.com/maps?q=Australia%20Melbourne%20Victoria'target="mapblast" style='text-decoration:none'>Melbourne</a> </font> </td> </tr>

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