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• SQL CE not loading from network share

  - by David Veeneman

  I installed VS 2010 RC yesterday, and suddenly, SQL Server CE isn't loading files from a network share. In projects compiled with VS 2008, if I try to open a SQL CE file located on a network share, I get an error that reads like this: Internal error: Cannot open the shared memory region. If I try to create a data connection in VS 2010 to a SQL CE file on a network share, I get this error: SQL Server Compact does not support opening database files on a network share. Can anyone shed any light on what's going on? Thanks.

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• Breaking through the class sealing

  - by Jason Crease

  Do you understand 'sealing' in C#?  Somewhat?  Anyway, here's the lowdown. I've done this article from a C# perspective, but I've occasionally referenced .NET when appropriate. What is sealing a class? By sealing a class in C#, you ensure that you ensure that no class can be derived from that class.  You do this by simply adding the word 'sealed' to a class definition: public sealed class Dog {} Now writing something like " public sealed class Hamster: Dog {} " you'll get a compile error like this: 'Hamster: cannot derive from sealed type 'Dog' If you look in an IL disassembler, you'll see a definition like this: .class public auto ansi sealed beforefieldinit Dog extends [mscorlib]System.Object Note the addition of the word 'sealed'. What about sealing methods? You can also seal overriding methods.  By adding the word 'sealed', you ensure that the method cannot be overridden in a derived class.  Consider the following code: public class Dog : Mammal { public sealed override void Go() { } } public class Mammal { public virtual void Go() { } } In this code, the method 'Go' in Dog is sealed.  It cannot be overridden in a subclass.  Writing this would cause a compile error: public class Dachshund : Dog { public override void Go() { } } However, we can 'new' a method with the same name.  This is essentially a new method; distinct from the 'Go' in the subclass: public class Terrier : Dog { public new void Go() { } } Sealing properties? You can also seal seal properties.  You add 'sealed' to the property definition, like so: public sealed override string Name {     get { return m_Name; }     set { m_Name = value; } } In C#, you can only seal a property, not the underlying setters/getters.  This is because C# offers no override syntax for setters or getters.  However, in underlying IL you seal the setter and getter methods individually - a property is just metadata. Why bother sealing? There are a few traditional reasons to seal: Invariance. Other people may want to derive from your class, even though your implementation may make successful derivation near-impossible.  There may be twisted, hacky logic that could never be second-guessed by another developer.  By sealing your class, you're protecting them from wasting their time.  The CLR team has sealed most of the framework classes, and I assume they did this for this reason. Security.  By deriving from your type, an attacker may gain access to functionality that enables him to hack your system.  I consider this a very weak security precaution. Speed.  If a class is sealed, then .NET doesn't need to consult the virtual-function-call table to find the actual type, since it knows that no derived type can exist.  Therefore, it could emit a 'call' instead of 'callvirt' or at least optimise the machine code, thus producing a performance benefit.  But I've done trials, and have been unable to demonstrate this If you have an example, please share! All in all, I'm not convinced that sealing is interesting or important.  Anyway, moving-on... What is automatically sealed? Value types and structs.  If they were not always sealed, all sorts of things would go wrong.  For instance, structs are laid-out inline within a class.  But what if you assigned a substruct to a struct field of that class?  There may be too many fields to fit. Static classes.  Static classes exist in C# but not .NET.  The C# compiler compiles a static class into an 'abstract sealed' class.  So static classes are already sealed in C#. Enumerations.  The CLR does not track the types of enumerations - it treats them as simple value types.  Hence, polymorphism would not work. What cannot be sealed? Interfaces.  Interfaces exist to be implemented, so sealing to prevent implementation is dumb.  But what if you could prevent interfaces from being extended (i.e. ban declarations like "public interface IMyInterface : ISealedInterface")?  There is no good reason to seal an interface like this.  Sealing finalizes behaviour, but interfaces have no intrinsic behaviour to finalize Abstract classes.  In IL you can create an abstract sealed class.  But C# syntax for this already exists - declaring a class as a 'static', so it forces you to declare it as such. Non-override methods.  If a method isn't declared as override it cannot be overridden, so sealing would make no difference.  Note this is stated from a C# perspective - the words are opposite in IL.  In IL, you have four choices in total: no declaration (which actually seals the method), 'virtual' (called 'override' in C#), 'sealed virtual' ('sealed override' in C#) and 'newslot virtual' ('new virtual' or 'virtual' in C#, depending on whether the method already exists in a base class). Methods that implement interface methods.  Methods that implement an interface method must be virtual, so cannot be sealed. Fields.  A field cannot be overridden, only hidden (using the 'new' keyword in C#), so sealing would make no sense.

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• Infiniband: a highperformance network fabric - Part I

  - by Karoly Vegh

  Introduction:At the OpenWorld this year I managed to chat with interesting people again - one of them answering Infiniband deepdive questions with ease by coffee turned out to be one of Oracle's IB engineers, Ted Kim, who actually actively participates in the Infiniband Trade Association and integrates Oracle solutions with this highspeed network. This is why I love attending OOW. He granted me an hour of his time to talk about IB. This post is mostly based on that tech interview.Start of the actual post: Traditionally datatransfer between servers and storage elements happens in networks with up to 10 gigabit/seconds or in SANs with up to 8 gbps fiberchannel connections. Happens. Well, data rather trickles through.But nowadays data amounts grow well over the TeraByte order of magnitude, and multisocket/multicore/multithread Servers hunger data that these transfer technologies just can't deliver fast enough, causing all CPUs of this world do one thing at the same speed - waiting for data. And once again, I/O is the bottleneck in computing. FC and Ethernet can't keep up. We have half-TB SSDs, dozens of TB RAM to store data to be modified in, but can't transfer it. Can't backup fast enough, can't replicate fast enough, can't synchronize fast enough, can't load fast enough. The bad news is, everyone is used to this, like back in the '80s everyone was used to start compile jobs and go for a coffee. Or on vacation. The good news is, there's an alternative. Not so-called "bleeding-edge" 8gbps, but (as of now) 56. Not layers of overhead, but low latency. And it is available now. It has been for a while, actually. Welcome to the world of Infiniband. Short history:Infiniband was born as a result of joint efforts of HPAQ, IBM, Intel, Sun and Microsoft. They planned to implement a next-generation I/O fabric, in the 90s. In the 2000s Infiniband (from now on: IB) was quite popular in the high-performance computing field, powering most of the top500 supercomputers. Then in the middle of the decade, Oracle realized its potential and used it as an interconnect backbone for the first Database Machine, the first Exadata. Since then, IB has been booming, Oracle utilizes and supports it in a large set of its HW products, it is the backbone of the famous Engineered Systems: Exadata, SPARC SuperCluster, Exalogic, OVCA and even the new DB backup/recovery box. You can also use it to make servers talk highspeed IP to eachother, or to a ZFS Storage Appliance. Following Oracle's lead, even IBM has jumped the wagon, and leverages IB in its PureFlex systems, their first InfiniBand Machines.IB Structural Overview: If you want to use IB in your servers, the first thing you will need is PCI cards, in IB terms Host Channel Adapters, or HCAs. Just like NICs for Ethernet, or HBAs for FC. In these you plug an IB cable, going to an IB switch providing connection to other IB HCAs. Of course you're going to need drivers for those in your OS. Yes, these are long-available for Solaris and Linux. Now, what protocols can you talk over IB? There's a range of choices. See, IB isn't accepting package loss like Ethernet does, and hence doesn't need to rely on TCP/IP as a workaround for resends. That is, you still can run IP over IB (IPoIB), and that is used in various cases for control functionality, but the datatransfer can run over more efficient protocols - like native IB. About PCI connectivity: IB cards, as you see are fast. They bring low latency, which is just as important as their bandwidth. Current IB cards run at 56 gbit/s. That is slightly more than double of the capacity of a PCI Gen2 slot (of ~25 gbit/s). And IB cards are equipped usually with two ports - that is, altogether you'd need 112 gbit/s PCI slots, to be able to utilize FDR IB cards in an active-active fashion. PCI Gen3 slots provide you with around ~50gbps. This is why the most IB cards are configured in an active-standby way if both ports are used. Once again the PCI slot is the bottleneck. Anyway, the new Oracle servers are equipped with Gen3 PCI slots, an the new IB HCAs support those too. Oracle utilizes the QDR HCAs, running at 40gbp/s brutto, which translates to a 32gbp/s net traffic due to the 10:8 signal-to-data information ratio. Consolidation techniques: Technology never stops to evolve. Mellanox is working on the 100 gbps (EDR) version already, which will be optical, since signal technology doesn't allow EDR to be copper. Also, I hear you say "100gbps? I will never use/need that much". Are you sure? Have you considered consolidation scenarios, where (for example with Oracle Virtual Network) you could consolidate your platform to a high densitiy virtualized solution providing many virtual 10gbps interfaces through that 100gbps? Technology never stops to evolve. I still remember when a 10mbps network was impressively fast. Back in those days, 16MB of RAM was a lot. Now we usually run servers with around 100.000 times more RAM. If network infrastrucure speends could grow as fast as main memory capacities, we'd have a different landscape now :) You can utilize SRIOV as well for consolidation. That is, if you run LDoms (aka Oracle VM Server for SPARC) you do not have to add physical IB cards to all your guest LDoms, and you do not need to run VIO devices through the hypervisor either (avoiding overhead). You can enable SRIOV on those IB cards, which practically virtualizes the PCI bus, and you can dedicate Physical- and Virtual Functions of the virtualized HCAs as native, physical HW devices to your guests. See Raghuram's excellent post explaining SRIOV. SRIOV for IB is supported since LDoms 3.1.  This post is getting lengthier, so I will rename it to Part I, and continue it in a second post. 

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• .NET TCPListener limitation ?

  - by Karnalta

  Hi all, I have a question about the usage of TCPListener in .NET... I am thinking about a client/server application and being new to this kind of application I have search a bit around the web and the solution which come the more often is to create a new thread for each new client connection. This solution seem fine but I was wondering if it was still usable with a application where you can have thousands of client at the same time ? Of course if there is thousands of client the application will not be hosted on a small desktop but on a real server, but is it the way to design an application for a large number of client ? Thank for help.

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• Try all available WSDL IPs with JAX-WS

  - by Asaf

  I'm using JAX-WS to open a service port. When the DNS exposes two IPs for the DNS entry (of the WSDL), the Service tries to use only the first - resulting in a "Failed to access the WSDL at: http://some.url.com/someDocument?wsdl. It failed with: Connection refused: connect" exception. I've found an issue filed against JAX-WS, but with no resolution. this is the comment that describes my problem best. The code is just a one-liner: Service service = Service.create("http://some.url.com/someDocument?wsdl", engineQName); the smarts is exposing those two A records on http://some.url.com/ at the DNS. Can anyone help? 10x,

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• What is the best server side solution for a real-time GPS tracking system

  - by Ayman

  Well, I tried to ask this question as a comment on this question, but I thought that maybe no one will notice it, so I decided to ask it as a separate one. The question is about how to do real-time GPS tracking system things; if we have the following scenario: Rather than connecting a GPS receiver to a PC, the user will have a mobile device with an integrated GPS receiver. Location data will be sent over mobile network using GPRS data connection to a server side. The data will be processed and a KML path file will be created and updated on time intervals and used to track the user using Google Earth. The question is: what is the best method to accomplish this scenario for the server side; is it a web service, a web application, a windows service, a windows application or what exactly? Taking into account that the system will serve a number of users simultaneously, and that more users may use the system in the future(scalability issues). Thank you in advance and I highly appreciate any help :)

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• How to use AIR 2.0 NativeProcess API with Java?

  - by dede

  How do you use this great new API in connection with Java? Do you use just pure native process API like nativeProcess.standardInput.write() and nativeProcess.standardOutput.read() with which you cannot debug Java side neither invoke remote java method. Or you are using some library that leverages remote method invocation such as flerry lib but that also cannot debug Java side? Or maybe you are using Merapi with which you can debug but cannot remotely invoke Java method? I'm asking this because this is maybe the most important question regarding this API and its ease of use.

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• Need help with ConnectionString value in C#

  - by SzamDev

  Hi I have an idea and I want to apply it to my Application (C# .NET). When we connect to a DB (MS SQL Server 2008) in VS 2008, the ConnectionString saved in the Application Setting and it's a static varriable (no one can edit it unless you edit it inside VS 2008). I want a way to let my Application search for MS SQL Server and save it to Application Setting and use it to connect to my DB Programmatically. When my application start, the first thing to do is checking the ConnectionString if vaild, NOT Empty and test connection to MS SQL Server Successfully so if there is a proplem I think to show a window form to let the user enter some data like username and password for MS SQL Server 2008 Is there any way to do it?

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• dataset tables row count 'zero'

  - by James123

  I am using dataadapter.Fill() into dataset. But dataset returning tables rows count zero (0). When I ran same sp in sql mgmt. It is returning two tables data. If attributeId = 1 Then spString = "USP_group_1" ElseIf attributeId = 2 Then spString = "USP_group_2" ElseIf attributeId = 3 Then spString = "USP_group_3" End If sqlcmd_q.CommandTimeout = 120 sqlcmd_q.Connection = sqlCnn sqlcmd_q.CommandText = spString sqlcmd_q.CommandType = CommandType.StoredProcedure sqlcmd_q.Parameters.AddWithValue("@client_id", clientId) Try sqlCnn.Open() Dim daGrid As New SqlDataAdapter(sqlcmd_q) daGrid.Fill(dsGrid) daGrid.Dispose() Return dsGrid I don't understand why this happening?

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• How to prevent "Local transaction already has 1 non-XA Resource" exception?

  - by Zeratul

  Hi, I'm using 2 PU in stateless EJB and each of them is invoked on one method: @PersistenceContext(unitName="PU") private EntityManager em; @PersistenceContext(unitName="PU2") private EntityManager em2; @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) public void getCandidates(final Integer eventId) throws ControllerException { ElectionEvent electionEvent = em.find(ElectionEvent.class, eventId); ... Person person = getPerson(candidate.getLogin()); ... } @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) private Person getPerson(String login) throws ControllerException { Person person = em2.find(Person.class, login); return person; } Those methods are annotated with REQUIRES_NEW transcaction to avoid this exception. When I was calling these method from javaFX applet, all worked as expected. Now I'm trying to call them from JAX-RS webservice (I don't see any logical difference as in both cases ejb was looked up in initial context) and I keep getting this exception. When I set up XADatasource in glassfish 2.1 connection pools, I got nullpointer exception on em2. Any ideas what to try next? Regards

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• How to navigate clicking row to another UITableView ?

  - by Meko

  Hi. I am trying to show detailed UItable view when clicking on row. I used - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. // AnotherViewController *anotherViewController = [[AnotherViewController alloc] initWithNibName:@"AnotherView" bundle:nil]; photoListViewController = [[PhotoListViewController alloc]initWithNibName:@"PhotoListViewController" bundle:[NSBundle mainBundle]]; [self.navigationController pushViewController:photoListViewController animated:YES]; [photoListViewController release]; // [self.navigationController pushViewController:anotherViewController]; // [anotherViewController release]; } This PhotoListViewController is an empty UITableViewController. As I know UITableViewCOntroller has a navigation controller implemented and I don`t have to create navigation controller. But When I clicked on row it does not navigate to second view.AM I have to make some connection on nib file?I only created this PhotoListViewController in File-New-UIViewCOntroller and selected UITableView. EDIT : SOLVED I solved my problem.I should use UINAvigation object.I thought that UITable has it but there was no ))

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• Best Design pattern for social media file transfer

  - by Onema

  Our system would like our clients to link their accounts with different social media sites like youtube, vimeo, facebook, myspace and so on. One of the benefits we would like to give to the user is to transfer, update and delete files they have uploaded to our sites and transfer them to the social media sites mentioned above. this files could be videos, images or audio. We started thinking about using a strategy pattern, as all of these sites share a common process ( authentication, connection, use the API to transfer/edit/delete the file ), but we soon realized that it may not work as me may want to use some of the extended functionality that is specific to each service (eg: associate a youtube video with a channel, or upload images to a specific album on facebook, and much, much more...) My question is, what would be the best Structural Design Patter to use for this scenario?

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• How to convert Facebook created_time to Java Date?

  - by smitty

  Hi, I have a FQL statement like this: String query = "SELECT post_id, actor_id, target_id, created_time, message FROM stream WHERE source_id in (SELECT target_id FROM connection WHERE source_id=<userID>) AND is_hidden = 0"; I just wondering what kind of time Facebook gives to me. The result of my statement will be mapped to a wrapper object (wallpost). myDate.setTime(wallpost.getCreated_time()); gives me no valid date. Does anyone have an idea what kind of date Facebook returns and how to match it to Date()? thanks in advance!

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• Is it possible to implement any kind of file upload recovery / resumption in a browser?

  - by Pete

  The project is a servlet to which people can upload files via, at present, HTTP POST. This is accompanied by Web page(s) providing a front-end to trigger the upload. We have more or less complete control over the servlet, and the Web pages, but don't want to impose any restrictions on the client beyond being a reasonably modern browser with Javascript. No Java applets etc. Files may potentially be large, and a possible use case is mobile devices on less reliable networks. Some people on the project are demanding the ability to resume an upload if the network connection goes down. I don't think this is possible with plain HTTP and Javascript in a browser, but I'd love to be proved wrong. Any suggestions?

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• SQL Server Compact with Visual Studio 2008

  - by Thomas

  I am running SQL server 2008 and Visual Studio 2008 on Vista. I downloaded SQL server compact 3.5 SP1 from Microsofts website and ran the install. When I open the server explorer for any windows application that I'm working on with VS 2008 and right click on data connections and then on add a connection a dialog comes up with available data providers. The problem is that SQL compact is not one of the options. Any idea why SQL compact is not showing up as a data provider in VS 2008?

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• Debugging with only the .exe

  - by Franklin Albricias

  HI: I've a Delphi 7 program that I wrote many years ago, but I've lost the source code. It's a small program but very useful for me. I've tried to 'install' it again in a new Windows XP computer, just copying the folder with de data (.db paradox files), and configured the BDE connection. When the programm starts I receive an "Unknown exception" and halts. I've no idea why this happens, and can't debug cause the lost source code. I've tried in another computer with the same results. Any suggestions or ideas? What do you do in a situation like this? Thanks in advance.

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• Surgical slave reads for Ruby on Rails, mulitple databases.

  - by Daniel

  Greetings, I'm currently working on a multiple database rails application. I want to off load the SELECT queries on to the slave databases for only SOME of the databases or specific models. The issue is that in places, we swap out the current database connection and put in a different one for a short time; to load fixtures or to handle sharding. Does anyone have any recommendations on a ruby gem that 1. will split select/(sql writes) with a considerable amount of control. We want to handle just some models and we are looking for a neat surgical fix. 2. does not monkey around with activerecord. 3. is still being maintained. TIA -daniel

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• java I/O is blocked while reading on socket when i put off the battery from device.

  - by gunjan goyal

  hi, i m working on client socket connection. client is a GPRS hardware device. i m receiving request from this client on my serversocket and then opening multiple threads. my problem is that when device/client close the socket then my IO detects that throws an exception but when i put off the battery from the device while sending the request to the serversocket it is blocked without throwing any exception. please help me out. thanks in advance. this is my code. try { while ((len = inputStream.read(mainBuffer)) -1) { System.out.println("len= " + len); }//end of while System.out.println("out of while loop");//which is never printed on screen. } catch (IOException e) { e.printStackTrace(); } regards gunjan goyal

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• custom MSSQL driver

  - by hoodoos

  I had a crazy thought about writing my own MSSQL driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing MSSQL client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# langauge. :)

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• WCF issues with KnownType for Dictionary

  - by Tom Frey

  Hi, I have a service that implements the following DataMember: [DataMember] public Dictionary<string, List<IOptionQueryResult>> QueryResultItems { get; set; } I have the class "OptionQuerySingleResult" which inherits from IOptionQueryResult. Now, I understand that I need to make the OptionQueryResult type "known" to the Service and thus tried to add the KnownType in various ways: [KnownType(typeof(Dictionary<string, OptionQuerySingleResult[]>))] [KnownType(typeof(Dictionary<string, List<OptionQuerySingleResult>>))] [KnownType(typeof(OptionQuerySingleResult)] However, none of those approaches worked and on the client side I'm either getting that deserialization failed or the server simply aborted the request, causing a connection aborted error. Does anyone have an idea on what's the proper way to get this to work? I'd like to add, the if I change the QueryResultItems definition to use the concrete type, instead of the interface, everything works just fine. Thanks, Tom

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• Amazon EC2 Load Balancer: Defending against DoS attack?

  - by netvope

  We usually blacklist IPs address with iptables. But in Amazon EC2, if a connection goes through the Elastic Load Balancer, the remote address will be replaced by the load balancer's address, rendering iptables useless. In the case for HTTP, apparently the only way to find out the real remote address is to look at the HTTP header HTTP_X_FORWARDED_FOR. To me, blocking IPs at the web application level is not an effective way. What is the best practice to defend against DoS attack in this scenario? In this article, someone suggested that we can replace Elastic Load Balancer with HAProxy. However, there are certain disadvantages in doing this, and I'm trying to see if there is any better alternatives.

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• C# and MySQL .NET Connector - Any way of preventing SQL Injection attacks in a generic class?

  - by John M

  My idea is to create some generic classes for Insert/Update/Select via a C# (3.5) Winforms app talking with a MySQL database via MySQL .NET Connector 6.2.2. For example: public void Insert(string strSQL) { if (this.OpenConnection() == true) { MySqlCommand cmd = new MySqlCommand(strSQL, connection); cmd.ExecuteNonQuery(); this.CloseConnection(); } } Then from anywhere in the program I can run a query with/without user input by just passing a SQL query string. Reading around on SO is starting to give me the indication that this may lead to SQL injection attacks (for any user-input values). Is there anyway of scrubbing the inputted strSQL or do I need to go and create individual parameterized queries in every method that needs to do a database function?

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• asp.net membership select provider

  - by Jonesy

  Hi folks, I've done this before but can't remember how for the life of me. I used aspnetreg_sql.exe to create the membership tables in my database. But now i cant seem to be able to point my web app to the correct database. In the provider settings in asp.net management interface i only see a radio button with the label "AspNetSqlProvider" but I can only test it (in which it always fails). I can't modify the connection. Can someone help me with this? Cheers, Billy

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• Client Web Service call over SSL using Apache Axis

  - by java_pill

  I'm using Apache Axis 1.5.1 to code a web service client connecting to a service over SSL. My application is running in Tomcat with SSL configuration setup in JKS. However, when I connect to the server, the connection is failing because the cert from our client is not being sent to the server. Is this something that has to be set in the client through code? Also note that the server does not need any user name or password authentication. With SSL turned off, everything works fine. Thanks,

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• Pear MDB2 class and raiserror exceptions in MSSQL

  - by drholzmichl

  Hi, in MSSQL it's possible to raise an error with raiserror(). I want to use a severity, which doesn't interrupt the connection. This error is raised in a stored procedure. In SQL Management Studio all is fine and I get my error code when executing this SP. But when trying to execute this SP via MDB2 in PHP5 this doesn't work. All I get is an empty array. MDB2 object is created via (including needed options): $db =& MDB2::connect($dsn); $db->setFetchMode(MDB2_FETCHMODE_ASSOC); $db->setOption('portability',MDB2_PORTABILITY_ALL ^ MDB2_PORTABILITY_EMPTY_TO_NULL); The following works (I get a PEAR error): $db->query("RAISERROR('test',11,0);"); But when calling a stored procedure which raises this error via $db->query("EXEC sp_raise_error"); there is not output. What's wrong?

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