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• how can we apply client side validation on fileupload control in ASP.NET to check filename contain s

  - by subodh

  I am working on ASP.NET3.5 platform. I have used a file upload control and a asp button to upload a file. Whenever i try to upload a file which contain special characterlike (file#&%.txt) it show crash and give the messeage Server Error in 'myapplication' Application. A potentially dangerous Request.Files value was detected from the client (filename="...\New Text &#.txt"). Description: Request Validation has detected a potentially dangerous client input value, and processing of the request has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site scripting attack. You can disable request validation by setting validateRequest=false in the Page directive or in the configuration section. However, it is strongly recommended that your application explicitly check all inputs in this case. Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Files value was detected from the client (filename="...\New Text &#.txt"). Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. how can i prevent this crash using javascript at client side?

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• How does static code run with multiple threads?

  - by Krisc

  I was reading http://stackoverflow.com/questions/1511798/threading-from-within-a-class-with-static-and-non-static-methods and I am in a similar situation. I have a static method that pulls data from a resource and creates some runtime objects based on the data. static class Worker{ public static MyObject DoWork(string filename){ MyObject mo = new MyObject(); // ... does some work return mo; } } The method takes awhile (in this case it is reading 5-10mb files) and returns an object. I want to take this method and use it in a multiple thread situation so I can read multiple files at once. Design issues / guidelines aside, how would multiple threads access this code? Let's say I have something like this... class ThreadedWorker { public void Run() { Thread t = new Thread(OnRun); t.Start(); } void OnRun() { MyObject mo = Worker.DoWork("somefilename"); mo.WriteToConsole(); } } Does the static method run for each thread, allowing for parallel execution?

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• C# KeyEvent doesn't log the enter/return key

  - by Pieter888

  Hey all, I've been making this login form in C# and I wanted to 'submit' all the data as soon as the user either clicks on submit or presses the enter/return key. I've been testing a bit with KeyEvents but nothing so far worked. void tbPassword_KeyPress(object sender, KeyPressEventArgs e) { MessageBox.Show(e.KeyChar.ToString()); } The above code was to test if the event even worked in the first place. It works perfectly, when I press 'd' it shows me 'd' when I press '8' it shows me '8' but pressing enter doesn't do anything. So I though this was because enter isn't really bound to a character but it did show backspace, it worked just fine so it got me confused about why it didn't register my enter key. So the question is: How do I log the enter/return key? and why doesn't it log the key press right right now like it should? note: I've put the event in a textbox tbPassword.KeyPress += new KeyPressEventHandler(tbPassword_KeyPress); So it fires when the enter button is pressed WHILE the textbox is selected (which is was the whole time of course) maybe that has something to do with the execution of the code.

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• Working with complex objects in Prevayler commands

  - by alexantd

  The demos included in the Prevayler distribution show how to pass in a couple strings (or something simple like that) into a command constructor in order to create or update an object. The problem is that I have an object called MyObject that has a lot of fields. If I had to pass all of them into the CreateMyObject command manually, it would be a pain. So an alternative I thought of is to pass my business object itself into the command, but to hang onto a clone of it (keeping in mind that I can't store the BO directly in the command). Of course after executing this command, I would need to make sure to dispose of the original copy that I passed in. public class CreateMyObject implements TransactionWithQuery { private MyObject object; public CreateMyObject(MyObject business_obj) { this.object = (MyObject) business_obj.clone(); } public Object executeAndQuery(...) throws Exception { ... } } The Prevayler wiki says: Transactions can't carry direct object references (pointers) to business objects. This has become known as the baptism problem because it's a common beginner pitfall. Direct object references don't work because once a transaction has been serialized to the journal and then deserialized for execution its object references no longer refer to the intended objects - - any objects they may have referred to at first will have been copied by the serialization process! Therefore, a transaction must carry some kind of string or numeric identifiers for any objects it wants to refer to, and it must look up the objects when it is executed. I think by cloning the passed-in object I will be getting around the "direct object pointer" problem, but I still don't know whether or not this is a good idea...

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• Python Error-Checking Standard Practice

  - by chaindriver

  Hi, I have a question regarding error checking in Python. Let's say I have a function that takes a file path as an input: def myFunction(filepath): infile = open(filepath) #etc etc... One possible precondition would be that the file should exist. There are a few possible ways to check for this precondition, and I'm just wondering what's the best way to do it. i) Check with an if-statement: if not os.path.exists(filepath): raise IOException('File does not exist: %s' % filepath) This is the way that I would usually do it, though the same IOException would be raised by Python if the file does not exist, even if I don't raise it. ii) Use assert to check for the precondition: assert os.path.exists(filepath), 'File does not exist: %s' % filepath Using asserts seems to be the "standard" way of checking for pre/postconditions, so I am tempted to use these. However, it is possible that these asserts are turned off when the -o flag is used during execution, which means that this check might potentially be turned off and that seems risky. iii) Don't handle the precondition at all This is because if filepath does not exist, there will be an exception generated anyway and the exception message is detailed enough for user to know that the file does not exist I'm just wondering which of the above is the standard practice that I should use for my codes.

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• C++ Exception Handling

  - by user1413793

  So I was writing some code and I noticed that apart from syntactical, type, and other compile-time errors, C++ does not throw any other exceptions. So I decided to test this out with a very trivial program: #include<iostream> int main() { std::count<<5/0<<std::endl; return 1 } When I compiled it using g++, g++ gave me a warning saying I was dividing by 0. But it still compiled the code. Then when I ran it, it printed some really large arbitrary number. When I want to know is, how does C++ deal with exceptions? Integer division by 0 should be a very trivial example of when an exception should be thrown and the program should terminate. Do I have to essentially enclose my entire program in a huge try block and then catch certain exceptions? I know in Python when an exception is thrown, the program will immediately terminate and print out the error. What does C++ do? Are there even runtime exceptions which stop execution and kill the program?

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• Can shared memory be read and validated without mutexes?

  - by Bribles

  On Linux I'm using shmget and shmat to setup a shared memory segment that one process will write to and one or more processes will read from. The data that is being shared is a few megabytes in size and when updated is completely rewritten; it's never partially updated. I have my shared memory segment laid out as follows: ------------------------- | t0 | actual data | t1 | ------------------------- where t0 and t1 are copies of the time when the writer began its update (with enough precision such that successive updates are guaranteed to have differing times). The writer first writes to t1, then copies in the data, then writes to t0. The reader on the other hand reads t0, then the data, then t1. If the reader gets the same value for t0 and t1 then it considers the data consistent and valid, if not, it tries again. Does this procedure ensure that if the reader thinks the data is valid then it actually is? Do I need to worry about out-of-order execution (OOE)? If so, would the reader using memcpy to get the entire shared memory segment overcome the OOE issues on the reader side? (This assumes that memcpy performs it's copy linearly and ascending through the address space. Is that assumption valid?)

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• Same query has nested loops when used with INSERT, but Hash Match without.

  - by AaronLS

  I have two tables, one has about 1500 records and the other has about 300000 child records. About a 1:200 ratio. I stage the parent table to a staging table, SomeParentTable_Staging, and then I stage all of it's child records, but I only want the ones that are related to the records I staged in the parent table. So I use the below query to perform this staging by joining with the parent tables staged data. --Stage child records INSERT INTO [dbo].[SomeChildTable_Staging] ([SomeChildTableId] ,[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 ) SELECT [SomeChildTableId] ,D.[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 FROM [dbo].[SomeChildTable] D INNER JOIN dbo.SomeParentTable_Staging I ON D.SomeParentTableID = I.SomeParentTableID; The execution plan indicates that the tables are being joined with a Nested Loop. When I run just the select portion of the query without the insert, the join is performed with Hash Match. So the select statement is the same, but in the context of an insert it uses the slower nested loop. I have added non-clustered index on the D.SomeParentTableID so that there is an index on both sides of the join. I.SomeParentTableID is a primary key with clustered index. Why does it use a nested loop for inserts that use a join? Is there a way to improve the performance of the join for the insert?

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• I need a fast runtime expression parser

  - by Chris Lively

  I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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• SQL Server full text query across multiple tables - why so slow?

  - by Mikey Cee

  Hi. I'm trying to understand the performance of an SQL Server 2008 full-text query I am constructing. The following query, using a full-text index, returns the correct results immediately: SELECT O.ID, O.Name FROM dbo.EventOccurrence O WHERE FREETEXT(O.Name, 'query') ie, all EventOccurrences with the word 'query' in their name. And the following query, using a full-text index from a different table, also returns straight away: SELECT V.ID, V.Name FROM dbo.Venue V WHERE FREETEXT(V.Name, 'query') ie. all Venues with the word 'query' in their name. But if I try to join the tables and do both full-text queries at once, it 12 seconds to return: SELECT O.ID, O.Name FROM dbo.EventOccurrence O INNER JOIN dbo.Event E ON O.EventID = E.ID INNER JOIN dbo.Venue V ON E.VenueID = V.ID WHERE FREETEXT(E.Name, 'search') OR FREETEXT(V.Name, 'search') Here is the execution plan: http://uploadpad.com/files/query.PNG From my reading, I didn't think it was even possible to make a free text query across multiple tables in this way, so I'm not sure I am understanding this correctly. Note that if I remove the WHERE clause from this last query then it returns all results within a second, so it's definitely the full-text that is causing the issue here. Can someone explain (i) why this is so slow and (ii) if this is even supported / if I am even understanding this correctly. Thanks in advance for your help.

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• Query broke down and left me stranded in the woods

  - by user1290323

  I am trying to execute a query that deletes all files from the images table that do not exist in the filters tables. I am skipping 3,500 of the latest files in the database as to sort of "Trim" the table back to 3,500 + "X" amount of records in the filters table. The filters table holds markers for the file, as well as the file id used in the images table. The code will run on a cron job. My Code: $sql = mysql_query("SELECT * FROM `images` ORDER BY `id` DESC") or die(mysql_error()); while($row = mysql_fetch_array($sql)){ $id = $row['id']; $file = $row['url']; $getId = mysql_query("SELECT `id` FROM `filter` WHERE `img_id` = '".$id."'") or die(mysql_error()); if(mysql_num_rows($getId) == 0){ $IdQue[] = $id; $FileQue[] = $file; } } for($i=3500; $i<$x; $i++){ mysql_query("DELETE FROM `images` WHERE id='".$IdQue[$i]."' LIMIT 1") or die("line 18".mysql_error()); unlink($FileQue[$i]) or die("file Not deleted"); } echo ($i-3500)." files deleted."; Output: 0 files deleted. Database contents: images table: 10,000 rows filters table: 63 rows Amount of rows in filters table that contain an images table id: 63 Execution time of php script: 4 seconds +/- 0.5 second Relevant DB structure TABLE: images id url etc... TABLE: filter id img_id (CONTAINS ID FROM images table) etc...

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• net send command program debugging in C#

  - by riad

  Dear all, I write a program to execute and send msg using windows net send command.Its working fine for single receptor.But the problem happen when i want to send message in many receptors. i use a for loop to take receptor name from a list box. Here all message go to the first receptor.The problem happen on process execution.So far i guess the process is not clear or dead on the time. Can any body guide me how i can send the msg to multiple users at a time? my code below: string sendingMessage = messageRichTextBox.Text; string[] recepentAddressArray = new string[recepentAddressListBox.Items.Count]; for (int j = 0; j < recepentAddressListBox.Items.Count; j++) // Getting address from list box { recepentAddressArray[j] = recepentAddressListBox.Items[j].ToString(); string recepantAddress = recepentAddressArray[j]; try { string strLine = "net send " + recepantAddress + " " + sendingMessage + " >C:netsend.log"; FileStream fs = new FileStream("c:netsend.bat", FileMode.Create, FileAccess.Write); StreamWriter streamWriter = new StreamWriter(fs); streamWriter.BaseStream.Seek(0, SeekOrigin.End); streamWriter.Write(strLine); streamWriter.Flush(); streamWriter.Close(); fs.Close(); Process p = new Process(); p.StartInfo.FileName = "C:netsend.bat"; p.StartInfo.WindowStyle = ProcessWindowStyle.Hidden; p.Start(); p.WaitForExit(); p.Close(); FileStream fsOutput = new FileStream("C:netsend.log", FileMode.Open, FileAccess.Read); StreamReader reader = new StreamReader(fsOutput); reader.BaseStream.Seek(0, SeekOrigin.Begin); string strOut = reader.ReadLine(); reader.Close(); fsOutput.Close(); } catch (Exception) { MessageBox.Show("ERROR"); } }

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• Delphi trace tool

  - by Max

  I was wondering if there's a tool or a component for Delphi that can trace method execution line by line and create a log file. With this kind of tool it is easy to compare how method performs on two sets of input data by comparing two log files. EDIT: Let's say there is a function 10: function MyFunction(aInput: Integer): Integer; 11: begin 12: if aInput 10 then 13: Result := 10 14: else 15: Result := 0; 16: end; I'm looking for a tool that would give the log which whould be similar to the following: When aInput parameter is 1: Line 10: 'function MyFunction(aInput: Integer): Integer;' Line 11: 'begin' Line 12: 'if aInput 10 then' Line 15: 'Result := 0;' Line 16: 'end;' and when aInput parameter is 11: Line 10: 'function MyFunction(aInput: Integer): Integer;' Line 11: 'begin' Line 12: 'if aInput 10 then' Line 13: 'Result := 10;' Line 16: 'end;' The only information that should be required by the tool is the function name. It's like stepping through the method under debugger, but in an automatic manner with logging every line of code.

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• JQuery submit form and output response or error message

  - by sergdev

  I want to submit form and show message about result. update_records initializes alert_message to error message. If success I expect that its value is changed. Than update_records outputs message. But the function always alerts "Error submitting form". What is wrong with this? The code follows: function update_records(form_name) { var options = { async: false, alert_message: "Error submitting form", success: function(message) { this.alert_message = message; } }; $('#' + form_name).ajaxSubmit(options); alert(options.alert_message); } I am newbie in Javascript/JSon/Jquery and I suspect that I misunderstand some basics of mentioned technologies. UPDATE: I specified "async:false" to make execution synchronous (Is it correct?) I also tried to insert delay between following two lines: $('#' + form_name).ajaxSubmit(options); pausecomp(1000); // inserted pause alert(options.alert_message); It also does not resolve the issue Function fo pousecomp follows: function pausecomp(millis) { var date = new Date(); var curDate = null; do { curDate = new Date(); } while(curDate-date < millis); }

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• LinqToSQL not updating database

  - by codegarten

  Hi. I created a database and dbml in visual studio 2010 using its wizards. Everything was working fine until i checked the tables data (also in visual studio server explorer) and none of my updates were there. using (var context = new CenasDataContext()) { context.Log = Console.Out; context.Cenas.InsertOnSubmit(new Cena() { id = 1}); context.SubmitChanges(); } This is the code i am using to update my database. At this point my database has one table with one field (PK) named ID. *INSERT INTO [dbo].Cenas VALUES (@p0) -- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1* This is LOG from the execution (printed the context log into the console). The problem i'm having is that these updates are not persistent in the database. I mean that when i query my database (visual studio server explorer - new query) i see the table is empty, every time. I am using a SQL Server database file (.mdf).

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• Deep Zoom in Ajax - Possible? Any examples out there?

  - by Phil

  I have an idea to implement a deep zoom type interface hosted in a browser for sports training data (speed, distance, heart rate etc.) However, rather than images I actually want to zoom into a hierarchy of information. For example, the initial display would contain a grid of years - hover over 2008, for example, and spin the mouse wheel (or click) will zoom into that year but during the zoom I want 2008 to fade out and be replaced with a calendar of months. Again zoom into a month and the months are replaced with the months calendar, zoom into a day and you finally see a chart with the training data plotted on it. All the time only dates with actual data would be highlighted in some fashion. My question is whether this would even be possible and whether anyone has seen examples of this already. I'm imagining that most of the time the next level of information could be cached in the browser (in fact, because this is calendar-based, I can calculate most of that and cache the dates to be highlighted.) I could also zoom into an empty chart whilst an Ajax thread is fetching the data to display. I've never tried anything like this before and I'm especially interested in whether DHTML would be capable of this sort of zoom (I suspect not and I would have to resort to Silverlight) and whether the Ajax execution would be uninterrupted whilst the browser rendering thread is kept busy zooming.

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• NUnit integration programmatically with spring

  - by harkon

  Hi! I have a component based architecture framework designed and I use NUnit for isolated testing - okay so far. Now I want to enable integration tests. Therefore the tests use real implementations of the existing components. Each element of the component has a life cycle (init, start and stop) and I created a NUnit component. In the start section the Console runner of the NUnit will be executed. Okay - now if I have a test fixture class in my dlls in the execution path the runner exectues them - fine! But: And this is crucial! Each to be tested implementation exists so far in the process and I want to use this instances for testing. If I use NUnit runner in the current way each instance will be created twice - and above all: I have a spring container and a implementation registry. Via this registry I can get access to all instances in the processes. But how do I give the test fixture access to the existing registry? Good: I can start the component architecture framework in the startup of the nunit runner - but this is not what I want. My guide is the apache Cactus framework (with JUnit and tomcat, JBoss etc.) Can someone help? Thanks a lot! Check: http://cone.codeplex.com

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• reload parent from within iframe

  - by Lauren

  I can't seem to reload the parent page from within an iframe... I've looked around at similar questions' answers but nothing has worked so far. The iframe I'm working with is here http://www.avaline.com/ R3000_3 once you log in, then hit the "order sample" button, and then hit "here" where it says "Your Third Party Shipper Numbers (To enter one, click here.)". I tried using javascript statements window.top.location.reload(),window.parent.location.reload(),window.parent.location.href=window.parent.location.href but none of those worked in FF 3.6 so I didn't move on to the other browsers although I am shooting for a cross-browser solution. I put the one-line javascript statements inside setTimeout("statement",2000) so people could read the content of the iframe (You have updated your shipper number(s). The page should refresh automatically. If not, please refresh and return to "order sample.") before the redirect happens, but that shouldn't affect the execution of the statements... I wish I could test and debug the statements with the Firebug console from within the Iframe but there doesn't seem to be any great way to test this out.

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• SQL Server Long Query

  - by thormj

  Ok... I don't understand why this query is taking so long (MSSQL Server 2005): [Typical output 3K rows, 5.5 minute execution time] SELECT dbo.Point.PointDriverID, dbo.Point.AssetID, dbo.Point.PointID, dbo.Point.PointTypeID, dbo.Point.PointName, dbo.Point.ForeignID, dbo.Pointtype.TrendInterval, coalesce(dbo.Point.trendpts,5) AS TrendPts, LastTimeStamp = PointDTTM, LastValue=PointValue, Timezone FROM dbo.Point LEFT JOIN dbo.PointType ON dbo.PointType.PointTypeID = dbo.Point.PointTypeID LEFT JOIN dbo.PointData ON dbo.Point.PointID = dbo.PointData.PointID AND PointDTTM = (SELECT Max(PointDTTM) FROM dbo.PointData WHERE PointData.PointID = Point.PointID) LEFT JOIN dbo.SiteAsset ON dbo.SiteAsset.AssetID = dbo.Point.AssetID LEFT JOIN dbo.Site ON dbo.Site.SiteID = dbo.SiteAsset.SiteID WHERE onlinetrended =1 and WantTrend=1 PointData is the biggun, but I thought its definition should allow me to pick up what I want easily enough: CREATE TABLE [dbo].[PointData]( [PointID] [int] NOT NULL, [PointDTTM] [datetime] NOT NULL, [PointValue] [real] NULL, [DataQuality] [tinyint] NULL, CONSTRAINT [PK_PointData_1] PRIMARY KEY CLUSTERED ( [PointID] ASC, [PointDTTM] ASC ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO CREATE NONCLUSTERED INDEX [IX_PointDataDesc] ON [dbo].[PointData] ( [PointID] ASC, [PointDTTM] DESC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] GO PointData is 550M rows, and Point (source of PointID) is only 28K rows. I tried making an Indexed View, but I can't figure out how to get the Last Timestamp/Value out of it in a compatible way (no Max, no subquery, no CTE). This runs twice an hour, and after it runs I put more data into those 3K PointID's that I selected. I thought about creating LastTime/LastValue tables directly into Point, but that seems like the wrong approach. Am I missing something, or should I rebuild something? (I'm also the DBA, but I know very little about A'ing a DB!)

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• How do I manage dependencies for automated builds on my build server?

  - by Tom Pickles

  I'm trying to implement continuous integration into our day to day workings. In our team, we're moving from just building our code in Visual Studio on our workstations and deploying, to using MSBuild.exe and automating on our build server (which is Jenkins) without the use of Visual Studio. We have external dependencies to references such as Automap in our projects. Because the automap (for example) dll isn't on the build server, the msbuild execution fails, for obvious reasons. There are other dll's which I need to be part of the build, I'm just using automap as an example. So what's the best way to get any dependencies onto the build server as part of the automated build? I've seen references to using a 'lib' folder, but I don't really understand where I should be putting it (in my project, filesystem, SVN ...?), and how the build server will get to it. I've also read that NuGet can do something with dependencies, but my build server isn't connected to the internet, and I don't understand how I can get my build to pull a NuGet package I may have created, and how it works together. Edit: I'm using subversion and we cannot use TeamCity as we would have to buy it and there's zero chance of funding.

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• get value from css using document.getElementById().style.height javascript

  - by Jamex

  Hi, Please offer insight into this mystery. I am trying to get the height value from a div box by var high = document.getElementById("hintdiv").style.height; alert(high); I can get this value just fine if the attribute is contained within the div tag, but it returns a blank value if the attribute is defined in the css section. This is fine, it shows 100px as a value. The value can be accessed. <div id="hintdiv" style="height:100px; display: none;"> . . var high = document.getElementById("hintdiv").style.height; alert(high); This is not fine, it shows an empty alert screen. The value is practically 0. #hintdiv { height:100px display: none; } <div id="hintdiv"> . . var high = document.getElementById("hintdiv").style.height; alert(high); But I have no problem accessing/changing the "display:none" attribute whether it is in the tag or in the css section. The div box displays correctly by both attribute definition methods (inside the tag or in the css section). I also tried to access the value by other variations, but no luck document.getElementById("hintdiv").style.height.value ----> undefined document.getElementById("hintdiv").height ---->undefined document.getElementById("hintdiv").height.value ----> error, no execution Any solution? TIA.

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• Class initialization and synchronized class method

  - by nybon

  Hi there, In my application, there is a class like below: public class Client { public synchronized static print() { System.out.println("hello"); } static { doSomething(); // which will take some time to complete } } This class will be used in a multi thread environment, many threads may call the Client.print() method simultaneously. I wonder if there is any chance that thread-1 triggers the class initialization, and before the class initialization complete, thread-2 enters into print method and print out the "hello" string? I see this behavior in a production system (64 bit JVM + Windows 2008R2), however, I cannot reproduce this behavior with a simple program in any environments. In Java language spec, section 12.4.1 (http://java.sun.com/docs/books/jls/second_edition/html/execution.doc.html), it says: A class or interface type T will be initialized immediately before the first occurrence of any one of the following: T is a class and an instance of T is created. T is a class and a static method declared by T is invoked. A static field declared by T is assigned. A static field declared by T is used and the reference to the field is not a compile-time constant (§15.28). References to compile-time constants must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field never cause initialization. According to this paragraph, the class initialization will take place before the invocation of the static method, however, it is not clear if the class initialization need to be completed before the invocation of the static method. JVM should mandate the completion of class initialization before entering its static method according to my intuition, and some of my experiment supports my guess. However, I did see the opposite behavior in another environment. Can someone shed me some light on this? Any help is appreciated, thanks.

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• Socket.Recieve Failing When Multithreaded

  - by Qua

  The following piece of code runs fine when parallelized to 4-5 threads, but starts to fail as the number of threads increase somewhere beyond 10 concurrentthreads int totalRecieved = 0; int recieved; StringBuilder contentSB = new StringBuilder(4000); while ((recieved = socket.Receive(buffer, SocketFlags.None)) > 0) { contentSB.Append(Encoding.ASCII.GetString(buffer, 0, recieved)); totalRecieved += recieved; } The Recieve method returns with zero bytes read, and if I continue calling the recieve method then I eventually get a 'An established connection was aborted by the software in your host machine'-exception. So I'm assuming that the host actually sent data and then closed the connection, but for some reason I never recieved it. I'm curious as to why this problem arises when there are a lot of threads. I'm thinking it must have something to do with the fact that each thread doesn't get as much execution time and therefore there are some idle time for the threads which causes this error. Just can't figure out why idle time would cause the socket not to recieve any data.

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• Why does first call to java.io.File.createTempFile(String,String,File) take 5 seconds on Citrix?

  - by Ben Roling

  While debugging slow startup of an Eclipse RCP app on a Citrix server, I came to find out that java.io.createTempFile(String,String,File) is taking 5 seconds. It does this only on the first execution and only for certain user accounts. Specifically, I am noticing it Citrix anonymous user accounts. I have not tried many other types of accounts, but this behavior is not exhibited with an administrator account. Also, it does not matter if the user has access to write to the given directory or not. If the user does not have access, the call will take 5 seconds to fail. If they do have access, the call with take 5 seconds to succeed. This is on a Windows 2003 Server. I've tried Sun's 1.6.0_16 and 1.6.0_19 JREs and see the same behavior. I googled a bit expecting this to be some sort of known issue, but didn't find anything. It seems like someone else would have had to have run into this before. The Eclipse Platform uses File.createTempFile() to test various directories to see if they are writeable during initialization and this issue adds 5 seconds to the startup time of our application. I imagine somebody has run into this before and might have some insight. Here is sample code I executed to see that it is indeed this call that is consuming the time. I also tried it with a second call to createTempFile and notice that subsequent calls return nearly instantaneously. public static void main(final String[] args) throws IOException { final File directory = new File(args[0]); final long startTime = System.currentTimeMillis(); File file = null; try { file = File.createTempFile("prefix", "suffix", directory); System.out.println(file.getAbsolutePath()); } finally { System.out.println(System.currentTimeMillis() - startTime); if (file != null) { file.delete(); } } } Sample output of this program is the following: C:\java.exe -jar filetest.jar C:/Temp C:\Temp\prefix8098550723198856667suffix 5093

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• Beginner Question: For extract a large subset of a table from MySQL, how does Indexing, order of tab

  - by chongman

  Sorry if this is too simple, but thanks in advance for helping. This is for MySQL but might be relevant for other RDMBSs tblA has 4 columns: colA, colB, colC, mydata, A_id It has about 10^9 records, with 10^3 distinct values for colA, colB, colC. tblB has 3 columns: colA, colB, B_id It has about 10^4 records. I want all the records from tblA (except the A_id) that have a match in tblB. In other words, I want to use tblB to describe the subset that I want to extract and then extract those records from tblA. Namely: SELECT a.colA, a.colB, a.colC, a.mydata FROM tblA as a INNER JOIN tblB as b ON a.colA=b.colA a.colB=b.colB ; It's taking a really long time (more than an hour) on a newish computer (4GB, Core2Quad, ubuntu), and I just want to check my understanding of the following optimization steps. ** Suppose this is the only query I will ever run on these tables. So ignore the need to run other queries. Now my questions: 1) What indexes should I create to optimize this query? I think I just need a multiple index on (colA, colB) for both tables. I don't think I need separate indexes for colA and colB. Another stack overflow article (that I can't find) mentioned that when adding new indexes, it is slower when there are existing indexes, so that might be a reason to use the multiple index. 2) Is INNER JOIN correct? I just want results where a match is found. 3) Is it faster if I join (tblA to tblB) or the other way around, (tblB to tblA)? This previous answer says that the optimizer should take care of that. 4) Does the order of the part after ON matter? This previous answer say that the optimizer also takes care of the execution order.

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