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• Read-only view of a Java list with more general type parameter

  - by Michael Rusch

  Suppose I have class Foo extends Superclass. I understand why I can't do this: List<Foo> fooList = getFooList(); List<Superclass> supList = fooList; But, it would seem reasonable for me to do that if supList were somehow "read-only". Then, everything would be consistent as everything that would come out of an objList would be a Foo, which is a Superclass. I could probably write a List implementation that would take an underlying list and a more general type parameter, and would then return everything as the more general type instead of the specific type. It would work like the return of Collections.unmodifiableList() except that the type would be made more general. Is there an easier way? The reason I'm considering doing this is that I am implementing an interface that requires that I return an (unmodifiable) List<Superclass>, but internally I need to use Foos, so I have a List<Foo>. I can't just cast.

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• How to make Stack.Pop threadsafe

  - by user260197

  I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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• forward/strong enum in VS2010

  - by Noah Roberts

  At http://blogs.msdn.com/vcblog/archive/2010/04/06/c-0x-core-language-features-in-vc10-the-table.aspx there is a table showing C++0x features that are implemented in 2010 RC. Among them are listed forwarding enums and strongly typed enums but they are listed as "partial". The main text of the article says that this means they are either incomplete or implemented in some non-standard way. So I've got VS2010RC and am playing around with the C++0x features. I can't figure these ones out and can't find any documentation on these two features. Not even the simplest attempts compile. enum class E { test }; int main() {} fails with: 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(518): error C2332: 'enum' : missing tag name 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(518): error C2236: unexpected 'class' 'E'. Did you forget a ';'? 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(518): error C3381: 'E' : assembly access specifiers are only available in code compiled with a /clr option 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(518): error C2143: syntax error : missing ';' before '}' 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(518): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== int main() { enum E : short; } Fails with: 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(513): warning C4480: nonstandard extension used: specifying underlying type for enum 'main::E' 1e:\dev_workspace\experimental\2010_feature_assessment\2010_feature_assessment\main.cpp(513): error C2059: syntax error : ';' ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== So it seems it must be some totally non-standard implementation that has allowed them to justify calling this feature "partially" done. How would I rewrite that code to access the forwarding and strong type feature?

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• CIL and JVM Little endian to big endian in c# and java

  - by Haythem

  Hello, I am using on the client C# where I am converting double values to byte array. I am using java on the server and I am using writeDouble and readDouble to convert double values to byte arrays. The problem is the double values from java at the end are not the double values at the begin giving to c# writeDouble in Java Converts the double argument to a long using the doubleToLongBits method , and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first. DoubleToLongBits Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout. The Program on the server is waiting of 64-102-112-0-0-0-0-0 from C# to convert it to 1700.0 but he si becoming 0000014415464 from c# after c# converted 1700.0 this is my code in c#: class User { double workingStatus; public void persist() { byte[] dataByte; using (MemoryStream ms = new MemoryStream()) { using (BinaryWriter bw = new BinaryWriter(ms)) { bw.Write(workingStatus); bw.Flush(); bw.Close(); } dataByte = ms.ToArray(); for (int j = 0; j < dataByte.Length; j++) { Console.Write(dataByte[j]); } } public double WorkingStatus { get { return workingStatus; } set { workingStatus = value; } } } class Test { static void Main() { User user = new User(); user.WorkingStatus = 1700.0; user.persist(); } thank you for the help.

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• How to get NSFormatter subclass to work with NSTableColumn sort key and selector?

  - by Andrew

  My setup: I have a sqlite database from which I populate a NSMutableArray of NSDictionary objects this is the DataSource for my NSTableView. One of the columns holds "time", the time is a float that holds seconds. I would like to display the values in this column as minutes:seconds. For instance my data would be 123.4329387 I want to display 2:03 which I have no problem doing with a subclass of NSFormatter (or NSNumberFormatter) applied to my NSTextField in the column. I have sorting set up by using the Table Column Attributes in IB, I just have the sort key set to "time" and the selector set to "compare:" which works fine without the formatter. Currently this gives me something like this when I sort (descending) 1:37, 1:31, 0:10, 0:10, 0:09, 1:30, 1:30, 1:26, 0:09 and similar nonsense, it looks like something is going on but it's definitely not sorted. How do I get the sort to look at the underlying data instead of the formatted value? Alternately, how do I specify a custom sort method and where do I put the code for said method? I have searched around quite a bit and have not found anything to help me out with this problem, any help with this is most appreciated.

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• Using stdint.h and ANSI printf?

  - by nn

  Hi, I'm writing a bignum library, and I want to use efficient data types to represent the digits. Particularly integer for the digit, and long (if strictly double the size of the integer) for intermediate representations when adding and multiplying. I will be using some C99 functionality, but trying to conform to ANSI C. Currently I have the following in my bignum library: #include <stdint.h> #if defined(__LP64__) || defined(__amd64) || defined(__x86_64) || defined(__amd64__) || defined(__amd64__) || defined(_LP64) typedef uint64_t u_w; typedef uint32_t u_hw; #define BIGNUM_DIGITS 2048 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT32_MAX #define U_HW_MIN UINT32_MIN #define U_W_MAX UINT64_MAX #define U_W_MIN UINT64_MIN #else typedef uint32_t u_w; typedef uint16_t u_hw; #define BIGNUM_DIGITS 4096 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT16_MAX #define U_HW_MIN UINT16_MIN #define U_W_MAX UINT32_MAX #define U_W_MIN UINT32_MIN #endif typedef struct bn { int sign; int n_digits; // #digits should exclude carry (digits = limbs) int carry; u_hw tab[BIGNUM_DIGITS]; } bn; As I haven't written a procedure to write the bignum in decimal, I have to analyze the intermediate array and printf the values of each digit. However I don't know which conversion specifier to use with printf. Preferably I would like to write to the terminal the digit encoded in hexadecimal. The underlying issue is, that I want two data types, one that is twice as long as the other, and further use them with printf using standard conversion specifiers. It would be ideal if int is 32bits and long is 64bits but I don't know how to guarantee this using a preprocessor, and when it comes time to use functions such as printf that solely rely on the standard types I no longer know what to use.

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• Using ReadOnlyCollection preventing me from setting up a bi-directional many-to-many relationship

  - by Kevin Pang

  I'm using NHibernate to persist a many-to-many relation between Users and Networks. I've set up both the User and Network class as follows, exposing each's collections as ReadOnlyCollections to prevent direct access to the underlying lists. I'm trying to make sure that the only way a User can be added to a Network is by using its "JoinNetwork" function. However, I can't seem to figure out how to add the User to the Network's list of users since its collection is readonly. public class User { private ISet<Network> _Networks = new HashedSet<Network>(); public ReadOnlyCollection<Network> Networks { get { return new List<Network>(_Networks).AsReadOnly(); } } public void JoinNetwork(Network network) { _Networks.Add(network); // How do I add the current user to the Network's list of users? } } public class Network { private ISet<User> _Users = new HashedSet<User>(); public ReadOnlyCollection<User> Users { get { return new List<User>(_Users).AsReadOnly(); } } }

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• Problem with DataTrigger binding - setters are not being called

  - by aoven

  I have a Command bound to a Button in XAML. When executed, the command changes a property value on the underlying DataContext. I would like the button's Content to reflect the new value of the property. This works*: <Button Command="{x:Static Member=local:MyCommands.TestCommand}" Content="{Binding Path=TestProperty, Mode=OneWay}" /> But this doesn't: <Button Command="{x:Static Member=local:MyCommands.TestCommand}"> <Button.Style> <Style TargetType="{x:Type Button}"> <Style.Triggers> <DataTrigger Binding="{Binding Path=TestProperty, Mode=OneWay}" Value="True"> <DataTrigger.Setters> <Setter Property="Content" Value="Yes"/> </DataTrigger.Setters> </DataTrigger> <DataTrigger Binding="{Binding Path=TestProperty, Mode=OneWay}" Value="False"> <DataTrigger.Setters> <Setter Property="Content" Value="No"/> </DataTrigger.Setters> </DataTrigger> </Style.Triggers> </Style> </Button.Style> </Button> Why is that? * By "works" I mean the Content gets updated whenever I click the button. TIA

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• Documentation for java.util.concurrent.locks.ReentrantReadWriteLock

  - by Andrei Taptunov

  Disclaimer: I'm not very good at Java and just comparing read/writer locks between C# and Java to understand this topic better & decisions behind both implementations. There is JavaDoc about ReentrantReadWriteLock. It states the following about upgrade/downgrade for locks: Lock downgrading ... However, upgrading from a read lock to the write lock is not possible. It also has the following example that shows manual upgrade from read lock to write lock: // Here is a code sketch showing how to exploit reentrancy // to perform lock downgrading after updating a cache void processCachedData() { rwl.readLock().lock(); if (!cacheValid) { // upgrade lock manually #1: rwl.readLock().unlock(); // must unlock first to obtain writelock #2: rwl.writeLock().lock(); if (!cacheValid) { // recheck ... } ... } use(data); rwl.readLock().unlock(); Does it mean that actually the sample from above may not behave correctly in some cases - I mean there is no lock between lines #1 & #2 and underlying structure is exposed to changes from other threads. So it can not be considered as the correct way to upgrade the lock or do I miss something here?

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• Self-referencing tables in Linq2Sql

  - by J-Man

  Hi, I've seen a lot of questions on self-referencing tables in Linq2Sql and how to eagerly load all child records for a particular root object. I've implemented a temporary solution by accessing all underlying properties, but you can see that this doesn't do the performance any good. The thing is though, that all records are correlated with each-other using a correlation GUID. Example below: RootElement - Id: 1 - ParentId: null - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 2 - ParentId: 1 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement2 - Id: 3 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 4 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD In my case, I do have access to the correlationId, so I can retrieve all of my records by performing the following query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' select element; But, of course, I want these elements associated with each other by executing this query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' && element.ParentId == null select element; My question is: is it possible to combine the results the first query as some sort of 'caching mechanism' for the query where I get the root element? Thanks for the input. J.

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• SQL Express under IIS 7.5

  - by fampinheiro

  I´m developing a web service that access a SQL Express database, it works very well in the Visual Studio host but when i deploy it to IIS 7.5 i get this exception. Please help me. Stack Trace: System.Data.EntityException: The underlying provider failed on Open. ---> System.Data.SqlClient.SqlException: Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed. at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.SqlClient.SqlConnection.Open() at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) --- End of inner exception stack trace --- at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) at System.Data.EntityClient.EntityConnection.Open() at System.Data.Objects.ObjectContext.EnsureConnection() at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source) at WSCinema.CinemaService.Movie() in D:\Documents\My Dropbox\Projects\sd.v0910\trab3\code\WSCinema\CinemaService.asmx.cs:line 46

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• Add new types to Go

  - by nevalu

  I'm trying add new types for that been managed/used as in Go core types. To create new types is anything very interesting to validate data before of send it to a non-SQL DBMS or to check data from a form. Go uses univeral constants to define them at global level: var DateType = universe.DefineType("date", universePos, &dateType{}) In this case they're defined to be called from a package like types: var Date = &dateType{} I get these errors: test.go:58: o.lit undefined (cannot refer to unexported field lit) test.go:62: *dateType is not Type missing Pos() token.Position The code is based on: http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go package main import ( "exp/eval" "fmt" // "go/token" ) // http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go type DateValue interface { eval.Value Get(*eval.Thread) string Set(*eval.Thread, string) } /* Date */ type dateV string func (v *dateV) String() string { return fmt.Sprint(*v) } func (v *dateV) Assign(t *eval.Thread, o eval.Value) { *v = dateV(o.(DateValue).Get(t)) } func (v *dateV) Get(*eval.Thread) string { return string(*v) } func (v *dateV) Set(t *eval.Thread, x string) { *v = dateV(x) } // http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go type Type interface { eval.Type // isDate returns true if this is a date type. isDate() bool } /* Common type */ type commonType struct{} // added func (commonType) isDate() bool { return false } /* Date */ type dateType struct { commonType } // * It should not be an universal constant //var universePos = token.Position{"<universe>", 0, 0, 0} // added //var DateType = universe.DefineType("date", universePos, &dateType{}) var Date = &dateType{} func (t *dateType) compat(o Type, conv bool) bool { t2, ok := o.lit().(*dateType) return ok && t == t2 } func (t *dateType) lit() Type { return t } func (t *dateType) isDate() bool { return true } func (t *dateType) String() string { return "<date>" } func (t *dateType) Zero() eval.Value { res := dateV("") return &res } /* Named types */ /* type NamedType struct { eval.NamedType Def Type }*/ type NamedType struct { // added // token.Position Name string // Underlying type. If incomplete is true, this will be nil. // If incomplete is false and this is still nil, then this is // a placeholder type representing an error. Def Type // True while this type is being defined. incomplete bool methods map[string]eval.Method } func (t *NamedType) isDate() bool { return t.Def.isDate() } /* *********************** */ func main() { print("foo") }

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• Why is it assumed that send may return with less than requested data transmitted on a blocking socke

  - by Ernelli

  The standard method to send data on a stream socket has always been to call send with a chunk of data to write, check the return value to see if all data was sent and then keep calling send again until the whole message has been accepted. For example this is a simple example of a common scheme: int send_all(int sock, unsigned char *buffer, int len) { int nsent; while(len 0) { nsent = send(sock, buffer, len, 0); if(nsent == -1) // error return -1; buffer += nsent; len -= nsent; } return 0; // ok, all data sent } Even the BSD manpage mentions that ...If no messages space is available at the socket to hold the message to be transmitted, then send() normally blocks... Which indicates that we should assume that send may return without sending all data. Now I find this rather broken but even W. Richard Stevens assumes this in his standard reference book about network programming, not in the beginning chapters, but the more advanced examples uses his own writen (write all data) function instead of calling write. Now I consider this still to be more or less broken, since if send is not able to transmit all data or accept the data in the underlying buffer and the socket is blocking, then send should block and return when the whole send request has been accepted. I mean, in the code example above, what will happen if send returns with less data sent is that it will be called right again with a new request. What has changed since last call? At max a few hundred CPU cycles have passed so the buffer is still full. If send now accepts the data why could'nt it accept it before? Otherwise we will end upp with an inefficient loop where we are trying to send data on a socket that cannot accept data and keep trying, or else? So it seems like the workaround, if needed, results in heavily inefficient code and in those circumstances blocking sockets should be avoided at all an non blocking sockets together with select should be used instead.

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• How to generate hibernate POJO classes programmatically?

  - by Vatsala

  Hi I am aware of the Hibernate Eclipse plugin that helps us (through a series of screens and button clicks) to generate the POJO and DAO classes for the underlying tables. But I would like to mimic this in a runtime environment, i.e. I would like to be able to do the exact same steps programmatically , where I should be able to supply the .cfg.xml file, the reveng.xml file, the database URL, the destination folder, via a command line/ parameters within main(String[] args).. Apparently there is no such tool available which works in a pure Hibernate scenario. There is one which is tuned to generate code for the spring framework - but thats not of direct use to me right now. I tried downloading hibernate-tools.jar's source code for the eclipse plugin, but right now the src code download link at hibernate.org(new design) has been disabled for some reason. Has anyone handled such a thing before? Or can you give me some clues to do this? I have tried a certain JDBCReader class's object, the rationale being read all tables using JDBCReader's methods and then figure out how to use hbm2POJO generator class....

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• Is it valid to use unsafe struct * as an opaque type instead of IntPtr in .NET Platform Invoke?

  - by David Jeske

  .NET Platform Invoke advocates declaring pointer types as IntPtr. For example, the following [DllImport("user32.dll")] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); However, I find when interfacing with interesting native interfaces, that have many pointer types, flattening everything into IntPtr makes the code very hard to read and removes the typical typechecking that a compiler can do. I've been using a pattern where I declare an unsafe struct to be an opaque pointer type. I can store this pointer type in a managed object, and the compiler can typecheck it form me. For example: class Foo { unsafe struct FOO {}; // opaque type unsafe FOO *my_foo; class if { [DllImport("mydll")] extern static unsafe FOO* get_foo(); [DllImport("mydll")] extern static unsafe void do_something_foo(FOO *foo); } public unsafe Foo() { this.my_foo = if.get_foo(); } public unsafe do_something_foo() { if.do_something_foo(this.my_foo); } While this example may not seem different than using IntPtr, when there are several pointer types moving between managed and native code, using these opaque pointer types for typechecking is a godsend. I have not run into any trouble using this technique in practice. However, I also have not seen an examples of anyone using this technique, and I wonder why. Is there any reason that the above code is invalid in the eyes of the .NET runtime? My main question is about how the .NET GC system treats "unsafe FOO *my_foo". Is this pointer something the GC system is going to try to trace, or is it simply going to ignore it? My hope is that because the underlying type is a struct, and it's declared unsafe, that the GC would ignore it. However, I don't know for sure. Thoughts?

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• Not possible to load DropDownList on FormView from code behind??

  - by tbone

  I have a UserControl, containing a FormView, containing a DropDownList. The FormView is bound to a data control. Like so: <asp:FormView ID="frmEdit" DataKeyNames="MetricCode" runat="server" DefaultMode="Edit" DataSourceID="llbDataSource" Cellpadding="0" > <EditItemTemplate> <asp:DropDownList ID="ParentMetricCode" runat="server" SelectedValue='<%# Bind("ParentMetricCode") %>' /> etc, etc I am trying to populate the DropDownList from the codebehind. If this was not contained in a FormView, I would normally just do it in the Page_Load event. However, that does not work within a FormView, as as soon as I try to do it, accessing the dropdownlist in code, ie: theListcontrol = CType(formView.FindControl(listControlName), System.Web.UI.WebControls.ListControl) ...the data binding mechansim of the FormView is invoked, which, of course, tries to bind the DropDownList to the underlying datasource, causing a *'ParentMetricCode' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value * error, since the DropDownList has not yet been populated. I tried performing the load in the DataBinding() event of the FormView, but then: theListcontrol = CType(formView.FindControl(listControlName), System.Web.UI.WebControls.ListControl) ...fails, as the FormView.Controls.Count = 0 at that point. Is this impossible? (I do not want to have to use a secondary ObjectDataSource to bind the dropdownlist to)

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• Linq-to-sql Add item and a one-to-many record at once

  - by Oskar Kjellin

  I have a function where I can add articles and users can comment on them. This is done with a one to many relationship like= "commentId=>ArticleId". However when I try to add the comment to the database at the same time as I add the one to many record, the commentId is not known. Like this code: Comment comment = new Comment(); comment.Date = DateTime.UtcNow; comment.Text = text; comment.UserId = userId; db.Comments.InsertOnSubmit(comment); comment.Articles.Add(new CommentsForArticle() { ArticleId = articleId, CommentId = comment.CommentId }); The commentId will be 0 before i press submit. Is there any way arround not having to submit in between or do I simply have to cut out the part where I have a one-to-many relationship and just use a CommentTable with a column like "ArticleId". What is best in a performance perspective? I understand the underlying issue, I just want to know which solution works best.

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• What is the difference between cubes and the Unified Dimensional Model (if any)?

  - by ngm

  I'm currently researching SQL Server 2008 as a business intelligence solution, and currently looking at Analysis Services (and I'm pretty new to business intelligence as a whole...) I'm a bit confused by some of the terms in SSAS, particularly the conceptual differences between cubes and MS's Unified Dimensional Model. I believe that a cube in SSAS is basically an OLAP cube -- dimensions, measures, something that sits between the underlying data source and a business user. But then that's kind of what I understand UDM to be as well. The docs for SQL Server 2005 seem to suggest as much: "A cube is essentially synonymous with a Unified Dimensional Model (UDM)". But then the SQL Server 2008 pages sort of suggest that UDM is a wrapper for both multidimensional data (cubes) and relational data: "Use the Unified Dimensional Model to provide one consolidated business view for relational and multidimensional data that includes business entities, business logic, calculations, and metrics." This blog post suggests similarly: "UDM provides a single dimensional model for all OLAP analysis and relational reporting needs. So you can use either MDX or SQL" Is UDM something that sits above cubes? Or are they the same thing? I presume I would develop cubes with the Cube Designer application; what would I develop a UDM with?

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• Extension Method for copying properties form object to another, with first attempt

  - by James

  Hi All, Im trying to write an extension method that I can use to copy values from one object property to another object of a different type, as long as the property names and types match exactly. This is what I have: public static T CopyFrom<T>(this T toObject, object fromObject) { var fromObjectType = fromObject.GetType(); var fromProperties = fromObjectType.GetProperties(); foreach (PropertyInfo toProperty in toObject.GetType().GetProperties()) { PropertyInfo fromProperty = fromObjectType.GetProperty(toProperty.Name); if (fromProperty != null) // match found { // check types var fromType = fromProperty.PropertyType.UnderlyingSystemType; var toType = toProperty.PropertyType.UnderlyingSystemType; if (toType.IsAssignableFrom(fromType)) { toProperty.SetValue(toObject, fromProperty.GetValue(fromObject, null), null); } } } return toObject; } This is working great for non boxed types, but Nullable<T> returns false when I call toType.IsAssignableFrom(fromType) because its type is Nullable<T> and is not the underlying type T. I read here that GetType() should unbox the Nullable<T> so it returns T but if I call that on PropertyInfo.PropertyType I get ReflectedMemberInfo and not the type T im looking for. I think im missing something obvious here, so I thought I would throw it open to SO to get some advice. Anyone have any ideas? Thanks, Jamee

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• C# string.Split() Matching Both Slashes?

  - by Sheep Slapper

  I've got a .NET 3.5 web application written in C# doing some URL rewriting that includes a file path, and I'm running into a problem. When I call string.Split('/') it matches both '/' and '\' characters. Is that... supposed to happen? I assumed that it would notice that the ASCII values were different and skip it, but it appears that I'm wrong. // url = 'someserver.com/user/token/files\subdir\file.jpg string[] buffer = url.Split('/'); The above code gives a string[] with 6 elements in it... which seems counter intuitive. Is there a way to force Split() to match ONLY the forward slash? Right now I'm lucky, since the offending slashes are at the end of the URL, I can just concatenate the rest of the elements in the string[], but it's a lot of work for what we're doing, and not a great solution to the underlying problem. Anyone run into this before? Have a simple answer? I appreciate it!

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• Obtaining touch location for a uiscrollview touch

  - by LOSnively

  I have a uiscrollview as an element of a uiscrollviewcontroller, along with other view objects. The image scrolls and zooms as expected, when the scrollView is the top subview. However, I also need to get the screen location of the touch, in particular when there is no scroll action. (I understand the location may change during a scroll, but that's not important.) I haven't found a way to do that. In the scrollviewcontroller implementation I have customized all of the standard methods that should do this: "touchesShouldBegin...", "touchesBegan:...", "touchesEnded:...", and so on. As far as I can tell, none of these are being called during a touch event when the scrollView is the top subview. I've tried setting the delayContentTouches property to both YES and NO, and that doesn't seem to make a difference. As an alternative, I've tried putting a UIView as the top subview and then tried passing the touches to the now underlying scrollView. In this configuration, the standard methods are called and I can get the touch location, but I haven't found a mechanism for the touches to be passed to the scrollView so scrolling occurs. Doing something like sending the touch messages to the specific scrollView, or to "super" or just sending them to nextResponder doesn't do it. It seems I can make the scroll work or find the location of the touch but not both, depending on what the "top" subview is. I suspect this is trivial, but after two weeks of struggling, it's time to eat my embarrassment for not being able to do this seemingly simplest of things. I've read all of the related questions here on stackoverflow, tried most if not all of the suggestions, and so far, nothing has worked. I've looked through the various links and references suggested by the answers, including Apple's documentation, but none have pointed out the gap in my understanding. Any ideas would be appreciated.

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• Retrieving dll version info via Win32 - VerQueryValue(...) crashes under Win7 x64

  - by user256890

  The respected open source .NET wrapper implementation (SharpBITS) of Windows BITS services fails identifying the underlying BITS version under Win7 x64. Here is the source code that fails. NativeMethods are native Win32 calls wrapped by .NET methods and decorated via DllImport attribute. private static BitsVersion GetBitsVersion() { try { string fileName = Path.Combine( System.Environment.SystemDirectory, "qmgr.dll"); int handle = 0; int size = NativeMethods.GetFileVersionInfoSize(fileName, out handle); if (size == 0) return BitsVersion.Bits0_0; byte[] buffer = new byte[size]; if (!NativeMethods.GetFileVersionInfo(fileName, handle, size, buffer)) { return BitsVersion.Bits0_0; } IntPtr subBlock = IntPtr.Zero; uint len = 0; if (!NativeMethods.VerQueryValue(buffer, @"\VarFileInfo\Translation", out subBlock, out len)) { return BitsVersion.Bits0_0; } int block1 = Marshal.ReadInt16(subBlock); int block2 = Marshal.ReadInt16((IntPtr)((int)subBlock + 2 )); string spv = string.Format( @"\StringFileInfo\{0:X4}{1:X4}\ProductVersion", block1, block2); string versionInfo; if (!NativeMethods.VerQueryValue(buffer, spv, out versionInfo, out len)) { return BitsVersion.Bits0_0; } ... The implementation follows the MSDN instructions by the letter. Still during the second VerQueryValue(...) call, the application crashes and kills the debug session without hesitation. Just a little more debug info right before the crash: spv = "\StringFileInfo\040904B0\ProductVersion" buffer = byte[1900] - full with binary data block1 = 1033 block2 = 1200 I looked at the targeted "C:\Windows\System32\qmgr.dll" file (The implementation of BITS) via Windows. It says that the Product Version is 7.5.7600.16385. Instead of crashing, this value should return in the verionInfo string. Any advice?

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• Dependency Injection and decoupling of software layers

  - by cs31415

  I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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• What's the best way to read a UDT from a database with Java?

  - by Lukas Eder

  I thought I knew everything about UDTs and JDBC until someone on SO pointed out some details of the Javadoc of java.sql.SQLInput and java.sql.SQLData JavaDoc to me. The essence of that hint was (from SQLInput): An input stream that contains a stream of values representing an instance of an SQL structured type or an SQL distinct type. This interface, used only for custom mapping, is used by the driver behind the scenes, and a programmer never directly invokes SQLInput methods. This is quite the opposite of what I am used to do (which is also used and stable in productive systems, when used with the Oracle JDBC driver): Implement SQLData and provide this implementation in a custom mapping to ResultSet.getObject(int index, Map mapping) The JDBC driver will then call-back on my custom type using the SQLData.readSQL(SQLInput stream, String typeName) method. I implement this method and read each field from the SQLInput stream. In the end, getObject() will return a correctly initialised instance of my SQLData implementation holding all data from the UDT. To me, this seems like the perfect way to implement such a custom mapping. Good reasons for going this way: I can use the standard API, instead of using vendor-specific classes such as oracle.sql.STRUCT, etc. I can generate source code from my UDTs, with appropriate getters/setters and other properties My questions: What do you think about my approach, implementing SQLData? Is it viable, even if the Javadoc states otherwise? What other ways of reading UDT's in Java do you know of? E.g. what does Spring do? what does Hibernate do? What does JPA do? What do you do? Addendum: UDT support and integration with stored procedures is one of the major features of jOOQ. jOOQ aims at hiding the more complex "JDBC facts" from client code, without hiding the underlying database architecture. If you have similar questions like the above, jOOQ might provide an answer to you.

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