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  • In Silverlight programming, how to prevent visitors from caching the downloaded content?

    - by suugaku
    Hi all, I want to create an online quiz website using Silverlight. When the registered users are logged in, they can view and answer the quiz once per page. To proceed to the next question, they must push next button, and the new data downloaded from the server. The previous questions are not cached. Thereby everytime the question is requested, the question will be reloaded from the server again. My question is how to do my scenario above in silverlight? Thank you in advance.

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  • What programming shortcuts do you end up regretting or backing out?

    - by bryanjonker
    I saw this question and it reminded me of AutoGenerateColumns in the old DataGrid. The few times I've used them, I ended up backing it out because I needed data formatting past the standard "spit out the Data Source columns." Likewise, with toggle, it sounds like it would save time, but then you end up needing to keep track of state or something else, and you rewrite the code accordingly. Are there things that you end up using thinking it will save you time, but end up backing out because it doesn't do what you need?

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  • What was the thinking behind the development of Object Oriented Programming?

    - by leeand00
    I've got some real nay-sayers on my hands here, and I'm trying to give them the reason why OOP was developed in the first place. I realize that OOP is not perfect for all problems and situations, but it was developed for a reason... My guess would be, that a few of those reasons would be: Maintainability Re-usability Document-ability Abstraction of Complex Technologies Dynamic Extension at Runtime... Probably some things that I'm not even aware of yet... But I really don't have much to back this up, and I was wondering why OOP was developed in the first place, and it's history. What were the people who developed OOP trying to accomplish? What led them to develop OOP?

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  • What's the silliest programming mistake you've ever done? [closed]

    - by bgo
    Despite not being a professional programmer, i use python or c to accomplish simple tasks. Once I needed a nasty equation to use with various data for physics lab. I thought that it would take a few hours if i used some mechanic calculator. Then i've written a python script to make things easier but something was wrong. After finding my mistakes one of which was forgetting to put ":", i realized that it had already took 2-3 hours, not to mention inventing satanic arithmetic techniques since i thought the errors was caused by my math :) Sometimes when you don't see it, you don't see it! Now i can find the syntax errors without thinking for a moment :) Any similar annoying mistakes that you've experienced?

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  • Where to begin with multi-threaded programming with c++?

    - by zoke
    I'm trying to implement my own IRC client as a personal proejct and I realized I needed a way to read and write from the socket at the same time. I realized I could have a reading thread which reads from the socket in the background and puts data in a queue and I could have another thread which writes data from a queue to the socket. However I have no idea on how to start with multithreaded programing or how to do it with c++. Where do I go from here?

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  • How broken is routing strategy that causes a martian packet (so far only) during tracepath?

    - by lkraav
    I believe I've achieved a table that routes packets from and to eth1/192.168.3.x through 192.168.3.1, and packets from and to eth0/192.168.1.x through 192.168.1.1 (helpful source). Question: when doing tracepath from 192.168.3.20 (from within vserver), I'm getting kernel: [318535.927489] martian source 192.168.3.20 from 212.47.223.33, on dev eth0 at or near the target IP, while intermediary hops go without (log below). I don't understand why this packet is arriving on eth0, instead of eth1, even after reading this: Note that you may see packets from non-routable IP addresses when running the traceroute or tracepath commands. While packets cannot be routed to these routers, packets sent between 2 routers only need to know the address of the next hop within the local networks, which could be a non-routable address. Can someone explain that paragraph in human language? Based on short initial trials so far, everything else seems to work without causing martians. Is this contained to the nature of tracepath operation or do I have some other bigger routing problem that will cause work traffic breakage? Side note: is it possible to inspect martian packet with tcpdump or wireshark or anything of the sort? I'm have not been able to get it to show up on my own. vserver-20 / # tracepath -n 212.47.223.33 1: 192.168.3.2 0.064ms pmtu 1500 1: 192.168.3.1 1.076ms 1: 192.168.3.1 1.259ms 2: 90.191.8.2 1.908ms 3: 90.190.134.194 2.595ms 4: 194.126.123.94 2.136ms asymm 5 5: 195.250.170.22 2.266ms asymm 6 6: 212.47.201.86 2.390ms asymm 7 7: no reply 8: no reply 9: no reply ^C Host routing: $ sudo ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo 2: sit0: <NOARP> mtu 1480 qdisc noop state DOWN link/sit 0.0.0.0 brd 0.0.0.0 3: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:24:1d:de:b3:5d brd ff:ff:ff:ff:ff:ff inet 192.168.1.2/24 scope global eth0 4: eth1: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:46:46:a3:6a brd ff:ff:ff:ff:ff:ff inet 192.168.3.2/27 scope global eth1 inet 192.168.3.20/27 brd 192.168.3.31 scope global secondary eth1 # linux-vserver instance $ sudo ip route default via 192.168.1.1 dev eth0 metric 3 unreachable 127.0.0.0/8 scope host 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.2 192.168.3.0/27 dev eth1 proto kernel scope link src 192.168.3.2 $ sudo ip rule 0: from all lookup local 32764: from all to 192.168.3.0/27 lookup dmz 32765: from 192.168.3.0/27 lookup dmz 32766: from all lookup main 32767: from all lookup default $ sudo ip route show table dmz default via 192.168.3.1 dev eth1 metric 4 192.168.3.0/27 dev eth1 scope link metric 4 Gateway routing # ip route 10.24.0.2 dev tun0 proto kernel scope link src 10.24.0.1 10.24.0.0/24 via 10.24.0.2 dev tun0 192.168.3.0/24 dev br-dmz proto kernel scope link src 192.168.3.1 192.168.1.0/24 dev br-lan proto kernel scope link src 192.168.1.1 $ISP_NET/23 dev eth0.1 proto kernel scope link src $WAN_IP default via $ISP_GW dev eth0.1 Additional background Options for non-virtualized network interface isolation?

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  • How can I improve my programming skills with out a computer (or reading material)?

    - by Tom Duckering
    Given the recent and continued chaos with grounded flights and folks stuck in airports, and what not, I'm wondering if anyone has any suggestions for activities that would help sharpen and develop a progammer's mind. The constraints are: Laptop is out of battery and there are no free sockets. You're bored of the book you're reading or you have none with you. Reasonable resources such as a pen and pad of paper are available. Rules can be bent within reason. As daft examples, things I have thought about are: How I might optimise the boarding of a plane. How I might improve the UI of a departure board.

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  • u32 filter udp lenght 0 to 29

    - by Mark Ocok
    Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21668 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21669 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21670 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21671 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 It's Spoofing attack dos, how to block Spoofing UDP lenght 0 to 29 using u32 Flooder target udp length udp 0 to 29

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  • soft lockup - CPU#0 stuck for 11s! error with Xen virtual machines

    - by Arun
    Getting a kernel panic with this error on my XEN VPS's. (all on 8.04 LTS) The kernel version on my Dom-0 is 2.6.24-25-xen and the kernel version on the Xen VPS is also 2.6.24-25-xen. I read something about disabling APIC from here http://muffinresearch.co.uk/archives/2008/08/20/ubuntu-bug-soft-lockup-cpu0-stuck-for-11s/ but that doesn't seem to help as well. Anyone experienced this and are there any workarounds? Thanks in advance!

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  • Interview Questions that can be asked on TCP/IP, UDP, Socket Programming ?

    - by Shantanu Gupta
    I am going for an interview day after tomorrow where i will be asked vaious questions related to TCP/IP and UDP. As of now i have prepared theoritical knowledge about it. But now I am looking up for gaining some practicle knowledge related to how it works in a network. What all is going in vaious .NET classes. I want to create a very small application like a chat or something that can make me all these concepts very much clear. Could you please suggest some questions related to TCP/IP that you generally ask or that you might have faced. How communication is going from server to client. Right now I am studying TcpClient, TcpListener and UdpClient Class but I want to implement all of them so as to get aware about its working. Is Chat application a Tcp/IP application ? I would appreciate your help.

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  • Route outbound connections from local network through VPN

    - by Sharkos
    I have a server A running OpenVPN, an OpenVPN client B (a rooted Android phone as it happens) and a third party C (a laptop, tablet etc.) tethered to B. B can use the VPN to access the internet via A; C can use the tethered connection WITHOUT the VPN to access the internet via B. However, with the VPN on B active, I cannot load information from the internet on C. A appears to log similar traffic inbound and outbound when B or C attempt to load a webpage, say, but the VPN on device B reports no inbound traffic when the connection originated from C. Where should I look for packets being dropped, and what ip rules should I use to make sure they are passed back through the VPN and into the local network B <- C? (I'll obviously post whatever further information is needed.) Further info Without VPN: root@android:/ # ip route default via [B's External Gateway] dev rmnet0 [B's External Subnet] dev rmnet0 proto kernel scope link src [B's External IP] [B's External Gateway] dev rmnet0 scope link 192.168.43.0/24 dev wlan0 proto kernel scope link src 192.168.43.1 With VPN: root@android:/ # ip route 0.0.0.0/1 dev tun0 scope link default via [B's External Gateway] dev rmnet0 [B's External Subnet] dev rmnet0 proto kernel scope link src [B's External IP] [B's External Gateway] dev rmnet0 scope link [External address of A] dev tun0 scope link 128.0.0.0/1 dev tun0 scope link 172.16.0.0/24 dev tun0 scope link 172.16.0.8/30 dev tun0 proto kernel scope link src 172.16.0.10 192.168.43.0/24 dev wlan0 proto kernel scope link src 192.168.43.1 192.168.168.0/24 dev tun0 scope link

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  • How does /burnmemory=XXX boot.ini switch work?

    - by user371602
    I know what the /burnmemory switch does on Windows, but I'd like to understand what Windows is doing under the hood to support it. It's described on msdn as the "amount of memory, in megabytes, that Windows cannot use". Does this mean simply that the kernel does not allow user virtual memory mapping into this area? How is this accomplished in the kernel, and are there other restrictions that the kernel will make when burnmemory is set?

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  • Is it wise to rely on default features of a programming language?

    - by George Edison
    Should I frequently rely on default values? For example, in PHP, if you have the following: <?php $var .= "Value"; ?> This is perfectly fine - it works. But what if assignment like this to a previously unused variable is later eliminated from the language? (I'm not referring to just general assignment to an unused variable.) There are countless examples of where the default value of something has changed and so much existing code was then useless. On the other hand, without default values, there is a lot of code redundancy. What is the proper way of dealing with this?

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  • Is two-finger non-homerow touch-typing for programming acceptable?

    - by codebliss
    I'm currently typing about 90 wpm (from http://speedtest.10-fast-fingers.com/ 90 correct 0 missed) using two fingers and the occasional ring or index. This probably grew from learning to type at an early age, before home-row was presented to me. Is this acceptable? Do people religiously endorse home-row even with low-mistake poking without looking at the keyboard?

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  • What would happen if a same file being read and appended at the same time(python programming)?

    - by Shane
    I'm writing a script using two separate thread one doing file reading operation and the other doing appending, both threads run fairly frequently. My question is, if one thread happens to read the file while the other is just in the middle of appending strings such as "This is a test" into this file, what would happen? I know if you are appending a smaller-than-buffer string, no matter how frequently you read the file in other threads, there would never be incomplete line such as "This i" appearing in your read file, I mean the os would either do: append "This is a test" - read info from the file; or: read info from the file - append "This is a test" to the file; and such would never happen: append "This i" - read info from the file - append "s a test". But if "This is a test" is big enough(assuming it's a bigger-than-buffer string), the os can't do appending job in one operation, so the appending job would be divided into two: first append "This i" to the file, then append "s a test", so in this kind of situation if I happen to read the file in the middle of the whole appending operation, would I get such result: append "This i" - read info from the file - append "s a test", which means I might read a file that includes an incomplete string?

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  • How do you deal with the more mundane parts of programming tasks?

    - by Uri
    My experience as a developer is that many projects or tickets are a mix of a short and focused very interesting task (e.g., designing some API or a platform to solve something) and a lot of repetitive and mundane tasks that cannot be automated (such as certain refactorings to use the API or platform, implementation of certain tests, some GUI handling, etc). I believe that this is the nature of our profession, unless we are high-level architects or managements and can delegate this work. The only item in my personal arsenal when dealing with these tasks is to devote some of my attention to radio or audiobooks (preferably not in English as I find it hard to concentrate on two "streams" of English at the same time). I maintain sufficient attention to carry the task and don't lose concentration as fast. I'm wondering how others cope with these and maintain concentration.

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  • Programming in Python; writing a Caesar Cipher using a zip() method

    - by user1068153
    I'm working on a python program for homework and the problem asks me to develop a program that encrypts a message using a caesar cipher. I need to be able to have the user input a number to shift the encryption by, such as 4: e.g. 'A' to 'E'. The user also needs to input the string to be translated. The book says to use a zip() to do the problem. I am confused on how I would do this though. I have this but it doesn't do anything >>>def ceasarCipher(string, shift): strings = ['abc', 'def'] shifts = [2,3] for string, shift in zip(strings, shifts): print ceasarCipher(string,shift) >>>string = 'hello world' >>>shift = 1

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • What is the difference between the * and the & operators in c programming?

    - by Wesley
    I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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