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• Python progression path - From apprentice to guru

  - by Morlock

  Hi all, I've been learning, working, and playing with Python for a year and a half now. As a biologist slowly making the turn to bio-informatics, this language has been a the very core of all the major contributions I have made in the lab. (bash and R scripts have helped some too. My C++ capabilities are very not functional yet). I more or less fell in love with the way Python permits me to express beautiful solutions and also with the semantics of the language that allows such a natural flow from thoughts to workable code. What I would like to know from you is your answer to a kind of question I have seldom seen in this or other forums. Let me sum up what I do NOT want to ask first ;) I don't want to know how to QUICKLY learn Python Nor do I want to find out the best way to get acquainted with the language Finally, I don't want to know a 'one trick that does it all' approach. What I do want to know your opinion about, is: What are the steps YOU would recommend to a Python journeyman, from apprenticeship to guru status (feel free to stop wherever your expertise dictates it), in order that one IMPROVES CONSTANTLY, becoming a better and better Python coder, one step at a time. The kind of answers I would enjoy (but feel free to surprise the readership :P ), is formatted more or less like this: Read this (eg: python tutorial), pay attention to that kind of details Code for so manytime/problems/lines of code Then, read this (eg: this or that book), but this time, pay attention to this Tackle a few real-life problems Then, proceed to reading Y. Be sure to grasp these concepts Code for X time Come back to such and such basics or move further to... (you get the point :) This process depicts an iterative Learn/Code cycle, and I really care about knowing your opinion on what exactly one should pay attention to, at various stages, in order to progress CONSTANTLY (with due efforts, of course). If you come from a specific field of expertise, discuss the path you see as appropriate in this field. Thanks a lot for sharing your opinions and good Python coding!

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• ASP Classic page quit working

  - by justSteve

  I've had a set of legacy pages running on my IIS7 server for at least a year. Sometime last week something changed and now this line: Response.Write CStr(myRS(0).name) & "=" & Cstr(myRS(0).value) which used to return nothing more exciting than the string: 'Updated=true' (the sproc processing input params, stores them to a table, checks for errors and when that's all done returns a success code by executing this statement: select 'true' as [Updated] Now my pageside error handler is being involved and offers: myError=Error from /logQuizScore.asp Error source: Microsoft VBScript runtime error Error number: 13 Error description: Type mismatch Important to note that all lots of pages use the same framework - same db, same coding format, connecitonstrings and (so far as I can tell) all others are working. Troubleshot to this point: The call to the stored procedure is working correctly (stuff is stored to the given table). The output from the stored procedure is working correctly (i can execute a direct call with the given parameters and stuff works. I can see profiler calling and passing. I can replace all code with 'select 'true' as updated' and the error is the same. everything up to the response.write statement above is correct. So something changed how ADO renders that particular recordset. So i try: Response.Write myRS.Item.count and get: Error number: 424 Error description: Object required The recordset object seems not to be instantiating but the command object _did execute. Repeat - lots of other pages just the same basic logic to hit other sprocs without a problem. full code snippet set cmd1 = Server.CreateObject("ADODB.Command") cmd1.ActiveConnection = MM_cnCompliance4_STRING cmd1.CommandText = "dbo._usp_UserAnswers_INSERT" ... cmd1.CommandType = 4 cmd1.CommandTimeout = 0 cmd1.Prepared = true set myRS = cmd1.Execute Response.Write CStr(myRS(0).name) & "=" & Cstr(myRS(0).value)

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• Simple iPhone drawing app with Quartz 2D

  - by Mr guy 4

  I am making a simple iPhone drawing program as a personal side-project. I capture touches event in a subclassed UIView and render the actual stuff to a seperate CGLayer. After each render, I call [self setNeedsLayout] and in the drawRect: method I draw the CGLayer to the screen context. This all works great and performs decently for drawing rectangles. However, I just want a simple "freehand" mode like a lot of other iPhone applications have. The way I thought to do this was to create a CGMutablePath, and simply: CGMutablePathRef path; -(void)touchBegan { path = CGMutablePathCreate(); } -(void)touchMoved { CGPathMoveToPoint(path,NULL,x,y); CGPathAddLineToPoint(path,NULL,x,y); } -(void)drawRect:(CGContextRef)context { CGContextBeginPath(context); CGContextAddPath(context,path); CGContextStrokePath(context); } However, after drawing for more than 1 second, performance degrades miserably. I would just draw each line into the off-screen CGLayer, if it were not for variable opacity! The less-than-100% opacity causes dots to be left on the screen connecting the lines. I have looked at CGContextSetBlendingMode() but alas I cannot find an answer. Can anyone point me in the right direction? Other iPhone apps are able to do this with very good efficiency.

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• Could not load type from assembly error

  - by George Mauer

  I have written the following simple test in trying to learn Castle Windsor's Fluent Interface: using NUnit.Framework; using Castle.Windsor; using System.Collections; using Castle.MicroKernel.Registration; namespace WindsorSample { public class MyComponent : IMyComponent { public MyComponent(int start_at) { this.Value = start_at; } public int Value { get; private set; } } public interface IMyComponent { int Value { get; } } [TestFixture] public class ConcreteImplFixture { [Test] public void ResolvingConcreteImplShouldInitialiseValue() { IWindsorContainer container = new WindsorContainer(); container.Register(Component.For<IMyComponent>().ImplementedBy<MyComponent>().Parameters(Parameter.ForKey("start_at").Eq("1"))); IMyComponent resolvedComp = container.Resolve<IMyComponent>(); Assert.AreEqual(resolvedComp.Value, 1); } } } When I execute the test through TestDriven.NET I get the following error: System.TypeLoadException : Could not load type 'Castle.MicroKernel.Registration.IRegistration' from assembly 'Castle.MicroKernel, Version=1.0.3.0, Culture=neutral, PublicKeyToken=407dd0808d44fbdc'. at WindsorSample.ConcreteImplFixture.ResolvingConcreteImplShouldInitialiseValue() When I execute the test through the NUnit GUI I get: WindsorSample.ConcreteImplFixture.ResolvingConcreteImplShouldInitialiseValue: System.IO.FileNotFoundException : Could not load file or assembly 'Castle.Windsor, Version=1.0.3.0, Culture=neutral, PublicKeyToken=407dd0808d44fbdc' or one of its dependencies. The system cannot find the file specified. If I open the Assembly that I am referencing in Reflector I can see its information is: Castle.MicroKernel, Version=1.0.3.0, Culture=neutral, PublicKeyToken=407dd0808d44fbdc and that it definitely contains Castle.MicroKernel.Registration.IRegistration What could be going on? I should mention that the binaries are taken from the latest build of Castle though I have never worked with nant so I didn't bother re-compiling from source and just took the files in the bin directory. I should also point out that my project compiles with no problem.

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• CPAN mirroring problem in cpan::mirrror

  - by user304122

  I am on a corporate PC that forces mcshield on everything that moves. I get blocked when trying to mirror on :- . . . . . . authors/id/J/JV/JV/EekBoek-2.00.01.tar.gz ... updated authors/id/J/JV/JV/CHECKSUMS ... updated Could not stat tmpfile '/cygdrive/t/cpan_mirror/authors/id/J/JW/JWIED/Mail-IspMailGate-1.1013.tar.gz-4712': No such file or directory at /usr/lib/perl5/site_perl/5.10/LWP/UserAgent.pm line 851. authors/id/J/JW/JWIED/Mail-IspMailGate-1.1013.tar.gz At this point, I get the Virus scanner mcshield sticking its Awr in. To maintain my mirror I execute:- #!/usr/bin/perl CPAN::Mini-update_mirror( remote = "http://mirror.eunet.fi/CPAN", local = "/cygdrive/t/cpan_mirror/", trace = 1, errors = 1, module_filters = [ qr/kjkjhkjhkjkj/i, qr/clamav/i, qr/ispmailgate/i, qr/IspMailGate/, qr/Mail-IspMailGate/, qr/mail-ispmailgate/i, ], path_filters = [ qr/ZZYYZZ/, #qr/WIED/, #qr/RJBS/, ] ); It skips OK if I enable the path_filter WIED. Just cannot get it to skip the module failing module to complete other WIED modules. Any ideas ?? .

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• how to do asynchronous http requests with epoll and python 3.1

  - by flow

  there is an interesting page http://scotdoyle.com/python-epoll-howto.html about how to do asnchronous / non-blocking / AIO http serving in python 3. there is the tornado web server which does include a non-blocking http client. i have managed to port parts of the server to python 3.1, but the implementation of the client requires pyCurl and seems to have problems (with one participant stating how ‘Libcurl is such a pain in the neck’, and looking at the incredibly ugly pyCurl page i doubt pyCurl will arrive in py3+ any time soon). now that epoll is available in the standard library, it should be possible to do asynchronous http requests out of the box with python. i really do not want to use asyncore or whatnot; epoll has a reputation for being the ideal tool for the task, and it is part of the python distribution, so using anything but epoll for non-blocking http is highly counterintuitive (prove me wrong if you feel like it). oh, and i feel threading is horrible. no threading. i use stackless. people further interested in the topic of asynchronous http should not miss out on this talk by peter portante at PyCon2010; also of interest is the keynote, where speaker antonio rodriguez at one point emphasizes the importance of having up-to-date web technology libraries right in the standard library.

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• Complete list of tools and technologies that make up a solid ASP.NET MVC 2 development environment f

  - by Dr Dork

  This question is related to another wiki I found on SO, but I'd like to develop a more comprehensive example of an automated ASP MVC 2 development environment that can be used to develop and deploy a wide range of small-scale websites by beginners. As far as characteristics of the dev environment go, I'd like to focus on beginner-friendly over powerful since the other wiki focuses more on advanced, powerful setups. This information is targeted for beginners (that already know C# and understand web dev concepts) that have selected... ASP.NET MVC 2 as their dev framework Visual Studio 2010 Pro (or 2008 Pro SP1) as their IDE Windows 7 as their OS and are looking for a quick and easy-to-setup environment that covers managing, building, testing, tracking, and deploying their website with as much automation as possible. A system that can be used for becoming familiar with the whole process, as well as a launching point for exploring other, more custom and powerful systems. Since we've already selected the Compiler, Framework, and OS, I'd like to develop ideas for... Code editor (unless you feel VS will suffice for all areas of code) Database and related tools Unit testing (VS?) Continuous integration build system (VS?) Project Planning Issue tracking Deployment (VS?) Source management (VS?) ASP, C#, VS, and related blogs that beginners can follow Any other categories I'm probably missing Since we're already using Visual Studio, I'd like to focus on the out-of-the-box solutions and features built into Visual Studio, unless you feel there are better solutions that work well with VS and are easier to use than the features built directly into VS. Thanks so much in advance for your wisdom!

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• How do you host multiple public facing websites on a VPS?

  - by Petras

  We host about 30 websites using typical shared hosting plans using ASP.NET and SQL 2000/2005/2008. I am now wondering about hosting all of these websites using our own virtual private server such as http://www.crystaltech.com/vps.aspx This is clearly cheaper but comes with a lot of questions I need answers to: Is the risk of having to keep this VPS server up and running worth it? Until now, the host provider has managed the server and we have not had to worry about crashes, downtime, software patches etc. We are not server administrators, we are programmers, so this is not really our expertise. On the other hand, it may not be hard to learn. When we make a website live, we log in to a domain management control panel and change the primary and secondary name servers to point to our shared web host: Eg ns1.sharedwebhost.com and ns2.sharedwebhost.com These name servers are going to have to change when we have a VPS. I don’t understand anything about how to set this up. Is there some useful info anyone could direct me to? Or is there software we need to install to make the primary and secondary name servers work on our VPS? The control panel we have for shared hosting comes with DNS management like this: What software would I need to install to create this for each site we host at a VPS? The control panel we have for shared hosting also comes with a POP email interface that allows email addresses to be added easily: Is this something that can be easily set up at a VPS so clients can manage their own email addresses? Is there software we need to install to make this work?

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• How to handle corrupt messages arriving on a socket?

  - by Pieter

  I've got a working socket handling mechanism, similar (but a bit more complex) to Qt's Fortune Example http://qt.nokia.com/doc/4.5/network-fortuneclient.html http://qt.nokia.com/doc/4.5/network-fortuneserver.html Now I'm wondering how to handle corrupt messages. Discarding the data is a start, but I need to discard up to a point I can start processing messages again. The corrupt message may be lost, but I need to be able to recover from it. I've got the following idea in mind: Put a fixed header at the start of each message, eg. 0xABCDEF01. When recovering, lookup this header and restart handling incoming messages. = Break off readFortune() on a timeout and recover = When encountering an inconsistent header, recover A huge blocksize is still going to be a problem. To fix that, I should be constantly checking whether or not I'm reading gibberish, but this is not always possible. I can also limit the blocksize on certain message-types. Any ideas on this? Any proposals on what to use as byteword?

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• WinForms DataGridView - update database

  - by Geo Ego

  I know this is a basic function of the DataGridView, but for some reason, I just can't get it to work. I just want the DataGridView on my Windows form to submit any changes made to it to the database when the user clicks the "Save" button. I populate the DataGridView according to a function triggered by a user selection in a DropDownList as follows: using (SqlConnection con = new SqlConnection(conString)) { con.Open(); SqlDataAdapter ruleTableDA = new SqlDataAdapter("SELECT rule.fldFluteType AS [Flute], rule.fldKnife AS [Knife], rule.fldScore AS [Score], rule.fldLowKnife AS [Low Knife], rule.fldMatrixScore AS [Matrix Score], rule.fldMatrix AS [Matrix] FROM dbo.tblRuleTypes rule WHERE rule.fldMachine_ID = '1003'", con); DataSet ruleTableDS = new DataSet(); ruleTableDA.Fill(ruleTableDS); RuleTable.DataSource = ruleTableDS.Tables[0]; } In my save function, I basically have the following (I've trimmed out some of the code around it to get to the point): using (SqlDataAdapter ruleTableDA = new SqlDataAdapter("SELECT rule.fldFluteType AS [Flute], rule.fldKnife AS [Knife], rule.fldScore AS [Score], rule.fldLowKnife AS [Low Knife], rule.fldMatrixScore AS [Matrix Score], rule.fldMatrix AS [Matrix] FROM dbo.tblRuleTypes rule WHERE rule.fldMachine_ID = '1003'", con)) { SqlCommandBuilder commandBuilder = new SqlCommandBuilder(ruleTableDA); DataTable dt = new DataTable(); dt = RuleTable.DataSource as DataTable; ruleTableDA.Fill(dt); ruleTableDA.Update(dt); } Okay, so I edited the code to do the following: build the commands, create a DataTable based on the DataGridView (RuleTable), fill the DataAdapter with the DataTable, and update the database. Now ruleTableDA.Update(dt) is throwing the exception "Concurrency violation: the UpdateCommand affected 0 of the expected 1 records."

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• Swig typecast to derived class?

  - by Zack

  I notice that Swig provides a whole host of functions to allow for typecasting objects to their parent classes. However, in C++ one can produce a function like the following: A * getAnObject() { if(someBoolean) return (A *) new B; else return (A *) new C; } Where "A" is the parent of classes "B" and "C". One can then typecast the pointer returned into being a "B" type or "C" type at one's convenience like: B * some_var = (B *) getAnObject(); Is there some way I can typecast an object I've received from a generic-pointer-producing function at run-time in the scripting language using the wrappers? (In my case, Lua?) I have a function that could produce one of about a hundred possible classes, and I'd like to avoid writing an enormous switch structure that I'd have to maintain in C++. At the point where I receive the generic pointer, I also have a string representation of the data type I'd like to cast it to. Any thoughts? Thanks! -- EDIT -- I notice that SWIG offers to generate copy constructors for all of my classes. If I had it generate those, could I do something like the following?: var = myModule.getAnObject(); -- Function that returns an object type-cast down to a pointer of the parent class, as in the function getAnObject() above. var = myModule.ClassThatExtendsBaseClass(var); -- A copy constructor that SWIG theoretically creates for me and have var then be an instance of the inheriting class that knows it's an instance of the inheriting class?

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• Iterating arrays in a batch file

  - by dboarman-FissureStudios

  I am writing a batch file (I asked a question on SU) to iterate over terminal servers searching for a specific user. So, I got the basic start of what I'm trying to do. Enter a user name Iterate terminal servers Display servers where user is found (they can be found on multiple servers now and again depending on how the connection is lost) Display a menu of options Iterating terminal servers I have: for /f "tokens=1" %%Q in ('query termserver') do (set __TermServers.%%Q) Now, I am getting the error... Environment variable __TermServers.SERVER1 not defined ...for each of the terminal servers. This is really the only thing in my batch file at this point. Any idea on why this error is occurring? Obviously, the variable is not defined, but I understood the SET command to do just that. I'm also thinking that in order to continue working on the iteration (each terminal server), I will need to do something like: :Search for /f "tokens=1" %%Q in ('query termserver') do (call Process) goto Break :Process for /f "tokens=1" %%U in ('query user %%username%% /server:%%Q') do (set __UserConnection = %%C) goto Search However, there are 2 things that bug me about this: Is the %%Q value still alive when calling Process? When I goto Search, will the for-loop be starting over? I'm doing this with the tools I have at my disposal, so as much as I'd like to hear about PowerShell and other ways to do this, it would be futile. I have notepad and that's it. Note: I would continue this line of questions on SuperUser, except that it seems to be getting more into programming specifics.

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• Javascript/Greasemonkey: search for something then set result as a value

  - by thewinchester

  Ok, I'm a bit of a n00b when it comes to JS (I'm not the greatest programmer) so please be gentle - specially if my questions been asked already somewhere and I'm too stupid to find the right answer. Self deprecation out of the way, let's get to the question. Problem There is a site me and a large group of friends frequently use which doesn't display all the information we may like to know - in this case an airline bookings site and the class of travel. While the information is buried in the code of the page, it isn't displayed anywhere to the user. Using a Greasemonkey script, I'd like to liberate this piece of information and display it in a suitable format. Here's the psuedocode of what I'm looking to do. Search dom for specified element define variables Find a string of text If found Set result to a variable Write contents to page at a specific location (before a specified div) If not found Do nothing I think I've achieved most of it so far, except for the key bits of: Searching for the string: The page needs to search for the following piece of text in the page HEAD: mileageRequest += "&CLASSES=S,S-S,S-S"; The Content I need to extract and store is between the second equals (=) sign and the last comma ("). The contents of this area can be any letter between A-Z. I'm not fussed about splitting it up into an array so I could use the elements individually at this stage. Writing the result to a location: Taking that found piece of text and writing it to another location. Code so far This is what I've come up so far, with bits missing highlighted. buttons = document.getElementById('buttons'); ''Search goes here var flightClasses = document.createElement("div"); flightClasses.innerHTML = '<div id="flightClasses"> ' + '<h2>Travel classes</h2>' + 'For the above segments, your flight classes are as follows:' + 'write result here' + '</div>'; main.parentNode.insertBefore(flightClasses, buttons); If anyone could help me, or point me in the right direction to finish this off I'd appreciate it.

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• Programming language shootout: code most like pseudocode for Dijkstra's Algorithm

  - by Casebash

  Okay, so this question here asked which language is most like executable pseudocode, so why not find out by actually writing some code! Here we have a competition where I will award a 100 point bounty (I know its not much, but I am poor after the recalc) to the code which most resembles this pseudocode. I've read through this a few times so I'm pretty sure that this pseudocode below is correct and about as unambiguous as pseudocode can be. Personally, I'm going to have a go in Python and probably Haskell as well, but I'm just learning the later so my attempt will probably be pretty poor. Note: Obviously to implement anything looking like this you'll have to define quite a few library functions. define DirectedGraph G with: Vertices as V, Edges as E define Vertex A, Z declare each e in E as having properties: Boolean fixed with: initial=false Real minSoFar with: initial=0 for A else infinity define PriorityQueue pq with: objects=V initial=A priority v=v.minSoFar create triggers for v in V: when v.minSoFar event reduced then pq.addOrUpdate v when v.fixed event becomesTrue then pq.remove v Repeat until Z.fixed==True: define Vertex U=pq.pop() U.fixed=True for Edge E adjacentTo U with other Vertex V: V.minSoFar=U.minSoFar+length(E) if reducesValue return Z.name, Z.minSoFar

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• Connecting to a Ghost User in Flex RTMFP

  - by Dan

  I have a simple Flex RTMFP P2P video app in the same mold as the Adobe Cirrus VideoPhone Sample application. A problem I've been encountering in developing this app (the same problem occurs in the sample) is when you try to connect to a ghost Stratus instance i.e you try to call someone whose Stratus id is in the database but who is no longer on the page. So here's an example of what I mean: Let's say you go to the Adobe Stratus sample and connect as Dan. Then open up a new tab, go to the sample again and connect as Fred. If from this point, you (as Fred) call Dan everything will work fine. But, if you close the tab in which you connected as Dan, and then from the Fred tab try to connect to Dan the program will just hang. I would have thought there would be a NetStream event that would be triggered if you tried to connect to a Stratus instance that is not longer online but I can't seem to find anything besides NetStream.Connect.Rejected which doesn't seem to be called. Any help is much appreciated!

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• Large Django application layout

  - by Rob Golding

  I am in a team developing a web-based university portal, which will be based on Django. We are still in the exploratory stages, and I am trying to find the best way to lay the project/development environment out. My initial idea is to develop the system as a Django "app", which contains sub-applications to separate out the different parts of the system. The reason I intended to make these "sub" applications is that they would not have any use outside the parent application whatsoever, so there would be little point in distributing them separately. We envisage that the portal will be installed in multiple locations (at different universities, for example) so the main app can be dropped into a number of Django projects to install it. We therefore have a different repository for each location's project, which is really just a settings.py file defining the installed portal applications, and a urls.py routing the urls to it. I have started to write some initial code, though, and I've come up against a problem. Some of the code that handles user authentication and profiles seems to be without a home. It doesn't conceptually belong in the portal application as it doesn't relate to the portal's functionality. It also, however, can't go in the project repository - as I would then be duplicating the code over each location's repository. If I then discovered a bug in this code, for example, I would have to manually replicate the fix over all of the location's project files. My idea for a fix is to make all the project repos a fork of a "master" location project, so that I can pull any changes from that master. I think this is messy though, and it means that I have one more repository to look after. I'm looking for a better way to achieve this project. Can anyone recommend a solution or a similar example I can take a look at? The problem seems to be that I am developing a Django project rather than just a Django application.

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• Web-design / UI advice

  - by Damian

  I'm working on a website on a Fmylife style. Now the homepage is the page showing the list of the latest posts. But I think there is a problem with that: The most "interesting" page is the one showing the top posts of the last days, but that page has very few visits compared to the main page. I suppose that's only because the main page is the "default" one. So, I've been thinking of making a home page that shows no posts (only one at the top of the page) but 4 big buttons showing the visitors what are the options to browse the content. But I'm also afraid that most users will not click any option and leave the site having seen no posts. So I don't know what to do. Obviously I have no idea of what will be good from a usability/efficiency point of view. Maybe a mix of the two options will be the best, but I don't know how to mix them. Any advice or idea will be greatly appreciated. The current home page looks like this: http://soquestion.latest.secretsapp.appspot.com/latest The new home page would look like this: http://soquestion.latest.secretsapp.appspot.com/

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• Filter Dynamically Calendar View SharePoint

  - by lerac

  Hello world I'm using SP wss 3.0 wondering if anybody knows how to filter a calendar view in SharePoint dynamically based upon the current user. It's not the simple question of using [ME] because this will not work with single line text fields. Also users do not add the items, they are being imported. So filtering on the basis of Created by, Modified by, Assigned to, or People picking data is not a option. Already managed to get to the current user in a jScript variable, now I would like to filter it in the calendar view. Been searching for a long time now, but can't seem to find anything. Altough filtering with a all items view is possible, yet I can't seem to find a way to dynamically filter a calendar view. Already tried modifing allitems.aspx view page in Designer Fooling around with CAML jScript (as far as I know) Calculated views Google (find more other cool things then a solution) Ofcourse I don't expect a solution on a silver platter (ofcourse would be nice ;) ), but if somebody can point me into a direction I already would be quite happy.

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• Cannot rollback ransaction with Entity Framework

  - by Luca

  I have to do queries on uncommitted changes and I tried to use transactions, but I found that it do not work if there are exceptions. I made a simple example to reproduce the problem. I have a database with only one table called "Tabella" and the table has two fields: "ID" is a autogenerated integer, and "Valore" is an integer with a Unique constraint. Then I try to run this code: using (TransactionScope scope = new TransactionScope()) { Db1Container db1 = new Db1Container(); try { db1.AddToTabella(new Tabella() { Valore = 1 }); db1.SaveChanges(); } catch { } try { db1.AddToTabella(new Tabella() { Valore = 1 }); db1.SaveChanges(); //Unique constraint is violated here and an exception is thrown } catch { } try { db1.AddToTabella(new Tabella() { Valore = 2 }); db1.SaveChanges(); } catch { } //scope.Complete(); //NEVER called } //here everything should be rolled back Now if I look into the database it should contain no records because the transaction should rollback, instead I find two records!!!! One with Valore=1 and one with Valore=2. I am missing something? It looks like the second call to SaveChanges method rollback its own changes and "deletes" the transaction, then the third call to SaveChanges commits the changes of the first and the third insert (at this point it is like the transaction not exists). I also tried to use SaveChanges(false) method (even without calling AcceptAllChanges method), but with no success: I have the same behaviour. I do not want the transaction to be rolled back automatically by SaveChanges, because I want to correct the errors (for example by user interaction in the catch statement) and make a retry. Can someone help me with this? It seems like a "bug", and it is giving me a really big headache...

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• iPhone SDK: Rendering a CGLayer into an image object

  - by codemercenary

  Hi all, I am trying to add a curved border around an image downloaded and to be displayed in a UITableViewCell. In the large view (ie one image on the screen) I have the following: productImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:product.image]]; [productImageView setAlpha:0.4]; productImageView.frame = CGRectMake(10.0, 30.0, 128.0, 128.0); CALayer *roundedlayer = [productImageView layer]; [roundedlayer setMasksToBounds:YES]; [roundedlayer setCornerRadius:7.0]; [roundedlayer setBorderWidth:2.0]; [roundedlayer setBorderColor:[[UIColor darkGrayColor] CGColor]]; [self addSubview:productImageView]; In the table view cell, to get it to scroll fast, an image needs to be drawn in the drawRect method of a UIView which is then added to a custom cell. so in drawRect - (void)drawRect:(CGRect)rect { ... point = CGPointMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP); //CALayer *roundedlayer = [productImageView layer]; //[roundedlayer setMasksToBounds:YES]; //[roundedlayer setCornerRadius:7.0]; //[roundedlayer setBorderWidth:2.0]; //[roundedlayer setBorderColor:[[UIColor darkGrayColor] CGColor]]; //[productImageView drawRect:CGRectMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP, IMAGE_WIDTH, IMAGE_HEIGHT)]; // [productImageView.image drawInRect:CGRectMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP, IMAGE_WIDTH, IMAGE_HEIGHT)]; So this works well, but if I remove the comment and try to show the rounded CA layer the scrolling goes really slow. To fix this I suppose I would have to render this image context into a different image object, and store this in an array, then set this image as something like: productImageView.image = (UIImage*)[imageArray objectAtIndex:indexPath.row]; My question is "How do I render this layer into an image?" TIA.

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• Editing a UITextField inside a UITableViewCell fails

  - by Stephen Darlington

  In my application I have a UITextField inside a UITableViewCell. If I click inside the text field and add some text I find that if try to move the insertion point it works the first time but fails on subsequent attempts. I am completely unable to move the selection; no "magnifying glass" appears. Even more curious, this "setting" seems to be permanent until I restart the application. And it affects all UITextFields on that screen and not just the one that I originally tried to edit. If you want to see it yourself, try the "UICatalog" sample that comes with the iPhone SDK. Click "text fields" and then "edit" and play around with the text boxes. I've done a lot of digging on this but it's pretty hard to Google for! The best references I've found are on Apple's support board and MacRumors formum (both reference a solution that apparently used to work on iPhone 2.0 but does work not with contemporary versions -- I did try). My feeling that is that this is a bug in the OS, but I thought I'd throw this out to the SO crowd for a second opinion and to see if there are any workarounds. Any ideas? Following benzado's suggestion, I tried building my application using the 2.0, 2.1 and 2.2 SDKs. I got the same behaviour in all versions. (Actually, something related but not the same broke in 2.2 but that's probably another question!)

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• Null Reference getting REMOTE_ADDR

  - by Josh

  I have an ASMX web service running under IIS7 in classic mode. This service has the following code: try { env.ExternalIP = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"]; } catch (Exception ex) { LogWriter.WriteError(ex); env.ExternalIP="000.000.000.000"; } This results in the following stack trace. I only modified the names of usercode call stack here to protect the innocent: Message: An Exception of type: NullReferenceException occured in method: GetAdditionalServerVar ExceptionMsg: Object reference not set to an instance of an object. ===Stack Trace=== at System.Web.Hosting.ISAPIWorkerRequestInProc.GetAdditionalServerVar(Int32 index) at System.Web.Hosting.ISAPIWorkerRequestInProc.GetServerVariable(String name) at System.Web.HttpRequest.AddServerVariableToCollection(String name) at System.Web.HttpRequest.FillInServerVariablesCollection() at System.Web.HttpServerVarsCollection.Populate() at System.Web.HttpServerVarsCollection.Get(String name) at System.Collections.Specialized.NameValueCollection.get_Item(String name) at MyService.MyMethod() I'm at a loss here as this is very basic plain vanilla code. EDIT This gets even stranger. I have added some basic code just wondering what server variables I can get at this point. This fails with the same exception when I try and get all the keys: System.NullReferenceException: Object reference not set to an instance of an object. at System.Web.Hosting.ISAPIWorkerRequestInProc.GetAdditionalServerVar(Int32 index) at System.Web.Hosting.ISAPIWorkerRequestInProc.GetServerVariable(String name) at System.Web.HttpRequest.AddServerVariableToCollection(String name) at System.Web.HttpRequest.FillInServerVariablesCollection() at System.Web.HttpServerVarsCollection.Populate() at System.Web.HttpServerVarsCollection.get_AllKeys() at MyService.MyHelper() When I was looking at the framework code looks like this could happen when the array which caches the server variables isn't populated and it looks like this occurs when there a null pointer to some Context...which seems like a fairly core piece of the framework code. I suppose it's time to burn up one of our support tickets with Microsoft.

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• Threading 101: What is a Dispatcher?

  - by Water Cooler v2

  Once upon a time, I remembered this stuff by heart. Over time, my understanding has diluted and I mean to refresh it. As I recall, any so called single threaded application has two threads: a) the primary thread that has a pointer to the main or DllMain entry points; and b) For applications that have some UI, a UI thread, a.k.a the secondary thread, on which the WndProc runs, i.e. the thread that executes the WndProc that recieves messages that Windows posts to it. In short, the thread that executes the Windows message loop. For UI apps, the primary thread is in a blocking state waiting for messages from Windows. When it recieves them, it queues them up and dispatches them to the message loop (WndProc) and the UI thread gets kick started. As per my understanding, the primary thread, which is in a blocking state, is this: C++ while(getmessage(/* args &msg, etc. */)) { translatemessage(&msg, 0, 0); dispatchmessage(&msg, 0, 0); } C# or VB.NET WinForms apps: Application.Run( new System.Windows.Forms() ); Is this what they call the Dispatcher? My questions are: a) Is my above understanding correct? b) What in the name of hell is the Dispatcher? c) Point me to a resource where I can get a better understanding of threads from a Windows/Win32 perspective and then tie it up with high level languages like C#. Petzold is sparing in his discussion on the subject in his epic work. Although I believe I have it somewhat right, a confirmation will be relieving.

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• Multiple asynchronous method calls to method while in a loop

  - by ranabra

  I have spent a whole day trying various ways using 'AddOnPreRenderCompleteAsync' and 'RegisterAsyncTask' but no success so far. I succeeded making the call to the DB asynchronous using 'BeginExecuteReader' and 'EndExecuteReader' but that is missing the point. The asynch handling should not be the call to the DB which in my case is fast, it should be afterwards, during the 'while' loop, while calling an external web-service. I think the simplified pseudo code will explain best: (Note: the connection string is using 'MultipleActiveResultSets') "Select ID, UserName from MyTable" 'Open connection to DB ExecuteReader(); if (DR.HasRows) {     while (DR.Read())     {         'Call external web-service         'and get current Temperature of each UserName - DR["UserName"].ToString()         'Update my local DB         Update MyTable set Temperature = ValueFromWebService where UserName =                                       DR["UserName"]         CmdUpdate.ExecuteNonQuery();     }     'Close connection etc } Accessing the DB is fast. Getting the returned result from the external web-service is slow and that at least should be handled Asynchnously. If each call to the web service takes just 1 second, assuming I have only 100 users it will take minimum 100 seconds for the DB update to complete, which obviously is not an option. There eventually should be thousands of users (currently only 2). Currently everything works, just very synchnously :) Thoughts to myself: Maybe my way of approaching this is wrong? Maybe the entire process should be called Asynchnously Many thanx

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• input type file alternative and file upload best practice

  - by Ioxp

  Background: I am working on a file upload page that will extend an existing web portal. This page will allow for an end user to upload files from there local computer to our network (the files will not be stored on the web server, rather a remote workstation). The end user will have the ability to view the data that they have submitted by hyper-linking the files that have been uploaded on this page. Question 1: Is there an ASP.net alternative to the <input type="file" runat="server" /> HTML tag? The reason for asking is i would rather use an image button and display the file as an asp label on the portal to keep with a consistent style. Question 2: So i understand that giving the end user the ability to upload files to the server and then turn around to show them the data that they posted poses a security threat. So far i am using the id.PostedFile.ContentType and the file extension to reject the data if its not an accepted format (i.e. "text/plain", "application/pdf", "application/vnd.ms-excel", or "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"). Also the location where the files are uploaded to has a sufficient amount of virus and malware protection and this is not a concern. What, from the C# point of view, additional steps should i take to ensure that the end user cant take advantage and compromise the system in regards to allowing them to upload files?

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