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• SATA errors reported during boot: exception Emask 0x40 SAct 0x0 SErr 0x80800 action 0x0

  - by digby280

  I have noticed some error during the Linux boot. They seem to continue to occur after the boot adding lines to the log every few seconds. Once booted this normally does not appear to be causing any problems. However, around 1 in 10 boots results in a kernel panic and the computer has on two or three occasions suddenly rebooted after being powered on for a number of hours. I presume the cause of the reboot is a kernel panic as well. I am running Ubuntu 11.10 and I have had Ubuntu installed on the computer for around a year. I have googled around and not found anything useful. I have provided the kernel log lines and the output of smartctl. Can anyone explain exactly what these errors mean, or better still how to resolve them? Apr 2 16:51:27 dell580 kernel: [ 19.831140] EXT4-fs (sdb2): re-mounted. Opts: errors=remount-ro,user_xattr,commit=0 Apr 2 16:51:27 dell580 kernel: [ 19.934194] tg3 0000:03:00.0: eth0: Link is down Apr 2 16:51:28 dell580 kernel: [ 20.929468] tg3 0000:03:00.0: eth0: Link is up at 100 Mbps, full duplex Apr 2 16:51:28 dell580 kernel: [ 20.929471] tg3 0000:03:00.0: eth0: Flow control is on for TX and on for RX Apr 2 16:51:28 dell580 kernel: [ 20.929727] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready Apr 2 16:51:29 dell580 kernel: [ 21.609381] EXT4-fs (sdb2): re-mounted. Opts: errors=remount-ro,user_xattr,commit=0 Apr 2 16:51:29 dell580 kernel: [ 21.616515] ata2.01: exception Emask 0x40 SAct 0x0 SErr 0x80800 action 0x0 Apr 2 16:51:29 dell580 kernel: [ 21.616519] ata2.01: SError: { HostInt 10B8B } Apr 2 16:51:29 dell580 kernel: [ 21.616525] ata2.00: hard resetting link Apr 2 16:51:29 dell580 kernel: [ 21.934036] ata2.01: hard resetting link Apr 2 16:51:29 dell580 kernel: [ 22.408890] ata2.00: SATA link up 1.5 Gbps (SStatus 113 SControl 300) Apr 2 16:51:29 dell580 kernel: [ 22.408907] ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Apr 2 16:51:29 dell580 kernel: [ 22.440934] ata2.00: configured for UDMA/100 Apr 2 16:51:29 dell580 kernel: [ 22.449040] ata2.01: configured for UDMA/133 Apr 2 16:51:29 dell580 kernel: [ 22.449818] ata2: EH complete Apr 2 16:51:33 dell580 kernel: [ 26.122664] ata2.01: exception Emask 0x40 SAct 0x0 SErr 0x80800 action 0x0 Apr 2 16:51:33 dell580 kernel: [ 26.122670] ata2.01: SError: { HostInt 10B8B } Apr 2 16:51:33 dell580 kernel: [ 26.122677] ata2.00: hard resetting link Apr 2 16:51:33 dell580 kernel: [ 26.442684] ata2.01: hard resetting link Apr 2 16:51:34 dell580 kernel: [ 26.925545] ata2.00: SATA link up 1.5 Gbps (SStatus 113 SControl 300) Apr 2 16:51:34 dell580 kernel: [ 26.925561] ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Apr 2 16:51:34 dell580 kernel: [ 26.961542] ata2.00: configured for UDMA/100 Apr 2 16:51:34 dell580 kernel: [ 26.969616] ata2.01: configured for UDMA/133 Apr 2 16:51:34 dell580 kernel: [ 26.970400] ata2: EH complete Apr 2 16:51:35 dell580 kernel: [ 28.111180] ata2.01: exception Emask 0x40 SAct 0x0 SErr 0x80800 action 0x0 Apr 2 16:51:35 dell580 kernel: [ 28.111184] ata2.01: SError: { HostInt 10B8B } Apr 2 16:51:35 dell580 kernel: [ 28.111191] ata2.00: hard resetting link Apr 2 16:51:35 dell580 kernel: [ 28.429674] ata2.01: hard resetting link Apr 2 16:51:36 dell580 kernel: [ 28.904557] ata2.00: SATA link up 1.5 Gbps (SStatus 113 SControl 300) Apr 2 16:51:36 dell580 kernel: [ 28.904572] ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Apr 2 16:51:36 dell580 kernel: [ 28.936609] ata2.00: configured for UDMA/100 Apr 2 16:51:36 dell580 kernel: [ 28.944692] ata2.01: configured for UDMA/133 Apr 2 16:51:36 dell580 kernel: [ 28.945464] ata2: EH complete Apr 2 16:51:38 dell580 kernel: [ 31.581756] eth0: no IPv6 routers present Apr 2 16:51:38 dell580 kernel: [ 32.103066] ata2.01: exception Emask 0x40 SAct 0x0 SErr 0x80800 action 0x0 Apr 2 16:51:38 dell580 kernel: [ 32.103074] ata2.01: SError: { HostInt 10B8B } Apr 2 16:51:38 dell580 kernel: [ 32.103085] ata2.00: hard resetting link Apr 2 16:51:38 dell580 kernel: [ 32.419669] ata2.01: hard resetting link Apr 2 16:51:39 dell580 kernel: [ 32.894518] ata2.00: SATA link up 1.5 Gbps (SStatus 113 SControl 300) Apr 2 16:51:39 dell580 kernel: [ 32.894533] ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Apr 2 16:51:39 dell580 kernel: [ 32.926536] ata2.00: configured for UDMA/100 Apr 2 16:51:39 dell580 kernel: [ 32.934715] ata2.01: configured for UDMA/133 Apr 2 16:51:39 dell580 kernel: [ 32.935578] ata2: EH complete Here's the output of smartctl for the drive. smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.0.0-17-generic] (local build) Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net === START OF INFORMATION SECTION === Model Family: SAMSUNG SpinPoint F1 DT Device Model: SAMSUNG HD103UJ Serial Number: S13PJ90QC19706 LU WWN Device Id: 5 0000f0 00b1c7960 Firmware Version: 1AA01113 User Capacity: 1,000,204,886,016 bytes [1.00 TB] Sector Size: 512 bytes logical/physical Device is: In smartctl database [for details use: -P show] ATA Version is: 8 ATA Standard is: ATA-8-ACS revision 3b Local Time is: Mon Apr 2 17:13:48 2012 BST SMART support is: Available - device has SMART capability. SMART support is: Enabled === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: PASSED General SMART Values: Offline data collection status: (0x00) Offline data collection activity was never started. Auto Offline Data Collection: Disabled. Self-test execution status: ( 41) The self-test routine was interrupted by the host with a hard or soft reset. Total time to complete Offline data collection: (11772) seconds. Offline data collection capabilities: (0x7b) SMART execute Offline immediate. Auto Offline data collection on/off support. Suspend Offline collection upon new command. Offline surface scan supported. Self-test supported. Conveyance Self-test supported. Selective Self-test supported. SMART capabilities: (0x0003) Saves SMART data before entering power-saving mode. Supports SMART auto save timer. Error logging capability: (0x01) Error logging supported. General Purpose Logging supported. Short self-test routine recommended polling time: ( 2) minutes. Extended self-test routine recommended polling time: ( 197) minutes. Conveyance self-test routine recommended polling time: ( 21) minutes. SCT capabilities: (0x003f) SCT Status supported. SCT Error Recovery Control supported. SCT Feature Control supported. SCT Data Table supported. SMART Attributes Data Structure revision number: 16 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 1 Raw_Read_Error_Rate 0x000f 100 100 051 Pre-fail Always - 0 3 Spin_Up_Time 0x0007 076 076 011 Pre-fail Always - 7940 4 Start_Stop_Count 0x0032 099 099 000 Old_age Always - 521 5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always - 0 7 Seek_Error_Rate 0x000f 253 253 051 Pre-fail Always - 0 8 Seek_Time_Performance 0x0025 100 100 015 Pre-fail Offline - 0 9 Power_On_Hours 0x0032 100 100 000 Old_age Always - 642 10 Spin_Retry_Count 0x0033 100 100 051 Pre-fail Always - 0 11 Calibration_Retry_Count 0x0012 100 100 000 Old_age Always - 0 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 482 13 Read_Soft_Error_Rate 0x000e 100 100 000 Old_age Always - 0 183 Runtime_Bad_Block 0x0032 100 100 000 Old_age Always - 759 184 End-to-End_Error 0x0033 100 100 000 Pre-fail Always - 0 187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0 188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0 190 Airflow_Temperature_Cel 0x0022 073 069 000 Old_age Always - 27 (Min/Max 16/27) 194 Temperature_Celsius 0x0022 073 067 000 Old_age Always - 27 (Min/Max 16/28) 195 Hardware_ECC_Recovered 0x001a 100 100 000 Old_age Always - 320028 196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 0 197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always - 0 198 Offline_Uncorrectable 0x0030 100 100 000 Old_age Offline - 0 199 UDMA_CRC_Error_Count 0x003e 099 099 000 Old_age Always - 1494 200 Multi_Zone_Error_Rate 0x000a 100 100 000 Old_age Always - 0 201 Soft_Read_Error_Rate 0x000a 253 253 000 Old_age Always - 0 SMART Error Log Version: 1 ATA Error Count: 211 (device log contains only the most recent five errors) CR = Command Register [HEX] FR = Features Register [HEX] SC = Sector Count Register [HEX] SN = Sector Number Register [HEX] CL = Cylinder Low Register [HEX] CH = Cylinder High Register [HEX] DH = Device/Head Register [HEX] DC = Device Command Register [HEX] ER = Error register [HEX] ST = Status register [HEX] Powered_Up_Time is measured from power on, and printed as DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes, SS=sec, and sss=millisec. It "wraps" after 49.710 days. Error 211 occurred at disk power-on lifetime: 0 hours (0 days + 0 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 84 51 0f 31 63 8f e1 Error: ICRC, ABRT 15 sectors at LBA = 0x018f6331 = 26174257 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- c8 00 00 40 62 8f e1 08 00:01:00.460 READ DMA c8 00 20 00 7c 30 e0 08 00:01:00.450 READ DMA c8 00 00 10 49 8f e1 08 00:01:00.440 READ DMA c8 00 e0 20 d0 30 e0 08 00:01:00.420 READ DMA c8 00 00 c0 59 90 e1 08 00:01:00.400 READ DMA Error 210 occurred at disk power-on lifetime: 0 hours (0 days + 0 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 84 51 cf e9 cf 66 e0 Error: ICRC, ABRT 207 sectors at LBA = 0x0066cfe9 = 6737897 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- c8 00 00 b8 cf 66 e0 08 00:08:29.780 READ DMA c8 00 60 60 c9 18 e0 08 00:08:29.770 READ DMA c8 00 40 20 c9 18 e0 08 00:08:29.770 READ DMA c8 00 20 00 c9 18 e0 08 00:08:29.760 READ DMA c8 00 20 98 cf 66 e0 08 00:08:29.750 READ DMA Error 209 occurred at disk power-on lifetime: 0 hours (0 days + 0 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 84 51 2f d1 74 e0 e0 Error: ICRC, ABRT 47 sectors at LBA = 0x00e074d1 = 14709969 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- c8 00 00 00 74 e0 e0 08 00:00:30.940 READ DMA c8 00 20 18 36 de e0 08 00:00:30.930 READ DMA c8 00 08 48 f1 dd e0 08 00:00:30.930 READ DMA c8 00 08 a8 f0 dd e0 08 00:00:30.930 READ DMA c8 00 08 90 f0 dd e0 08 00:00:30.930 READ DMA Error 208 occurred at disk power-on lifetime: 0 hours (0 days + 0 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 84 51 7f 21 88 9d e0 Error: ICRC, ABRT 127 sectors at LBA = 0x009d8821 = 10324001 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- c8 00 a0 00 88 9d e0 08 00:00:27.610 READ DMA c8 00 58 a8 e7 9c e0 08 00:00:27.610 READ DMA c8 00 00 28 e6 9c e0 08 00:00:27.610 READ DMA c8 00 00 e0 e4 9c e0 08 00:00:27.610 READ DMA c8 00 00 90 e0 9c e0 08 00:00:27.600 READ DMA Error 207 occurred at disk power-on lifetime: 0 hours (0 days + 0 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 04 51 26 6a 6a c3 e0 Error: ABRT at LBA = 0x00c36a6a = 12806762 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- ca 00 00 90 69 c3 e0 08 00:29:39.350 WRITE DMA ca 00 40 90 68 c3 e0 08 00:29:39.350 WRITE DMA ca 00 40 50 65 c3 e0 08 00:29:39.350 WRITE DMA ca 00 40 d0 64 c3 e0 08 00:29:39.350 WRITE DMA ca 00 40 90 63 c3 e0 08 00:29:39.350 WRITE DMA SMART Self-test log structure revision number 1 Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error # 1 Short offline Interrupted (host reset) 90% 638 - # 2 Short offline Interrupted (host reset) 90% 638 - # 3 Extended offline Interrupted (host reset) 90% 638 - # 4 Short offline Interrupted (host reset) 90% 638 - # 5 Extended offline Interrupted (host reset) 90% 638 - SMART Selective self-test log data structure revision number 1 SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS 1 0 0 Not_testing 2 0 0 Not_testing 3 0 0 Not_testing 4 0 0 Not_testing 5 0 0 Not_testing Selective self-test flags (0x0): After scanning selected spans, do NOT read-scan remainder of disk. If Selective self-test is pending on power-up, resume after 0 minute delay.

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• Thoughts on exception handling.

  - by AndyScott

  Was working on a windows form app (something I haven't done in a while), adding threading and logging so that it would work a little more smoothly and have a record of who did what.  I was just about at the point where I was going to check it into source control when I noticed that the Output window was showing "A first chance exception of type 'System.InvalidCastException' occurred in mscorlib.dll", so I googled it.  In reading some threads about the error, I came across the following comment and it got me thinking: "In addition, while they should be avoided if possible, exceptions are a quite legitimate part of program execution. It's their going unhandled that is a real issue, because that means crashy, crashy." How do you normally use exception handling?  I feel that exceptions are intended to handle errors in code (in my experience generally related to bad data making its way into the system).  Now don't get me wrong, I understand that exceptions happen and should be dealt with, but I feel that they are a "last resort" to keep a program from crashing, but should never be a way to pass data or continue logical processing that could be handled in standard code flow. I mention this, because I have seen it done. What do you think?

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• Is there a way of recover from an Exception in Directory.EnumerateFiles ?

  - by Magnus Johansson

  In .NET 4, there's this Directory.EnumerateFiles() method with recursion that seems handy. However, if an Exception occurs within a recursion, how can I continue/recover from that and continuing enumerate the rest of the files? try { var files = from file in Directory.EnumerateFiles(@"c:\", "*.*", SearchOption.AllDirectories) select new { File = file }; Console.WriteLine(files.Count().ToString()); } catch (UnauthorizedAccessException uEx) { Console.WriteLine(uEx.Message); } catch (PathTooLongException ptlEx) { Console.WriteLine(ptlEx.Message); }

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• Visual Studio: What happened to the "Break when an exception is unhandled" option?

  - by Adrian Grigore

  Hi, As far as I remember, Visual Studio (both 2008 and 2010) used to have an option to break either on thrown exceptions or on unhandled exceptions. Now when I bring up the Exceptions dialog (Ctr+Alt+E), it just offers to break when an exception is thrown: http://screencast.com/t/NDk3NDYxZD I've tried resizing to the columns in that dialog, but that did not help. Is this a bug, or am I missing something?

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• Oracle JDBC connection exception in Solaris but not Windows?

  - by lupefiasco

  I have some Java code that connects to an Oracle database using DriverManager.getConnection(). It works just fine on my Windows XP machine. However, when running the same code on a Solaris machine, I get the following exception. Both machines can reach the database machine on the network. I have included the Oracle trace logs. Mar 23, 2010 12:12:33 PM org.apache.commons.configuration.ConfigurationUtils locate FINE: ConfigurationUtils.locate(): base is /users/theUser/ADCompare, name is props.txt Mar 23, 2010 12:12:33 PM org.apache.commons.configuration.ConfigurationUtils locate FINE: Loading configuration from the path /users/theUser/ADCompare/props.txt Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver connect FINE: OracleDriver.connect(url=jdbc:oracle:thin:@//theServer:1521/theService, info) Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver connect FINER: OracleDriver.connect() walletLocation:(null) Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver parseUrl FINER: OracleDriver.parseUrl(url=jdbc:oracle:thin:@//theServer:1521/theService) Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver parseUrl FINER: sub_sub_index=12, end=46, next_colon_index=16, user=17, slash=18, at_sign=17 Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver parseUrl FINER: OracleDriver.parseUrl(url):return Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.OracleDriver connect FINER: user=theUser, password=******, database=//theServer:1521/theService, protocol=thin, prefetch=null, batch=null, accumulate batch result =true, remarks=null, synonyms=null Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.PhysicalConnection <init> FINE: PhysicalConnection.PhysicalConnection(ur="jdbc:oracle:thin:@//theServer:1521/theService", us="theUser", p="******", db="//theServer:1521/theService", info) Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.PhysicalConnection <init> FINEST: PhysicalConnection.PhysicalConnection() : connectionProperties={user=theUser, password=******, protocol=thin} Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.PhysicalConnection initialize FINE: PhysicalConnection.initialize(ur="jdbc:oracle:thin:@//theServer:1521/theService", us="theUser", access) Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.PhysicalConnection initialize FINE: PhysicalConnection.initialize(ur, us):return Mar 23, 2010 12:12:33 PM oracle.jdbc.driver.PhysicalConnection needLine FINE: PhysicalConnection.needLine()--no return java.lang.ArrayIndexOutOfBoundsException: 31 at oracle.net.nl.NVTokens.parseTokens(Unknown Source) at oracle.net.nl.NVFactory.createNVPair(Unknown Source) at oracle.net.nl.NLParamParser.addNLPListElement(Unknown Source) at oracle.net.nl.NLParamParser.initializeNlpa(Unknown Source) at oracle.net.nl.NLParamParser.<init>(Unknown Source) at oracle.net.resolver.TNSNamesNamingAdapter.loadFile(Unknown Source) at oracle.net.resolver.TNSNamesNamingAdapter.checkAndReload(Unknown Source) at oracle.net.resolver.TNSNamesNamingAdapter.resolve(Unknown Source) at oracle.net.resolver.NameResolver.resolveName(Unknown Source) at oracle.net.resolver.AddrResolution.resolveAndExecute(Unknown Source) at oracle.net.ns.NSProtocol.establishConnection(Unknown Source) at oracle.net.ns.NSProtocol.connect(Unknown Source) at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1037) at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:282) at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:468) at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:165) at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:35) at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:839) at java.sql.DriverManager.getConnection(DriverManager.java:582) at java.sql.DriverManager.getConnection(DriverManager.java:185) The above exception is also thrown if I use OracleDataSource instead of the generic DriverManager.getConnection(). Any ideas on why the behavior is different in the different environments?

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• Can a stack have an exception safe method for returning and removing the top element with move seman

  - by Motti

  In an answer to a question about std::stack::pop() I claimed that the reason pop does not return the value is for exception safety reason (what happens if the copy constructor throws). @Konrad commented that now with move semantics this is no longer relevant. Is this true? AFAIK, move constructors can throw, but perhaps with noexcept it can still be achieved. For bonus points what thread safety guarantees can this operation supply?

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• Most appropriate exception for a collection not being initialised?

  - by Brian Scott

  What is the most appropriate .Net exception type for when you have a class which must have its collection property initialised with at least one item? I'm thinking that it would be an ArgumentOutOfRangeException but is there something more appropriate based on a collection?

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• What exception type to throw for unrecognized ID paramater?

  - by fearofawhackplanet

  ITool GetTool(Guid tool) { if (tool = Hammer.Id) return new Hammer(); else if (tool = Drill.Id) return new Drill(); else throw new ....? } What's the most appropriate exception type to throw here? NotSupportedException is the closest I've found but I don't think that's quite right.

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• .NET and C# Exceptions. What is it reasonable to catch.

  - by djna

  Disclaimer, I'm from a Java background. I don't do much C#. There's a great deal of transfer between the two worlds, but of course there are differences and one is in the way Exceptions tend to be thought about. I recently answered a C# question suggesting that under some circstances it's reasonable to do this: try { some work } catch (Exeption e) { commonExceptionHandler(); } (The reasons why are immaterial). I got a response that I don't quite understand: until .NET 4.0, it's very bad to catch Exception. It means you catch various low-level fatal errors and so disguise bugs. It also means that in the event of some kind of corruption that triggers such an exception, any open finally blocks on the stack will be executed, so even if the callExceptionReporter fuunction tries to log and quit, it may not even get to that point (the finally blocks may throw again, or cause more corruption, or delete something important from the disk or database). May I'm more confused than I realise, but I don't agree with some of that. Please would other folks comment. I understand that there are many low level Exceptions we don't want to swallow. My commonExceptionHandler() function could reasonably rethrow those. This seems consistent with this answer to a related question. Which does say "Depending on your context it can be acceptable to use catch(...), providing the exception is re-thrown." So I conclude using catch (Exception ) is not always evil, silently swallowing certain exceptions is. The phrase "Until .NET 4 it is very bad to Catch Exception" What changes in .NET 4? IS this a reference to AggregateException, which may give us some new things to do with exceptions we catch, but I don't think changes the fundamental "don't swallow" rule. The next phrase really bothers be. Can this be right? It also means that in the event of some kind of corruption that triggers such an exception, any open finally blocks on the stack will be executed (the finally blocks may throw again, or cause more corruption, or delete something important from the disk or database) My understanding is that if some low level code had lowLevelMethod() { try { lowestLevelMethod(); } finally { some really important stuff } } and in my code I call lowLevel(); try { lowLevel() } catch (Exception e) { exception handling and maybe rethrowing } Whether or not I catch Exception this has no effect whatever on the excution of the finally block. By the time we leave lowLevelMethod() the finally has already run. If the finally is going to do any of the bad things, such as corrupt my disk, then it will do so. My catching the Exception made no difference. If It reaches my Exception block I need to do the right thing, but I can't be the cause of dmis-executing finallys

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• How to handle "null primary key encountered" exception in eclipselink?

  - by den-javamaniac

  Hi. I'm catching ... Null primary key encountered in unit of work clone ... exception in eclipselink(2.0.2 with 2.0 jpa) literally meaning that id in my entity is <=0 (for primitive types). Though debug here states that everything's fine and I have nothing to worry about. My AS is glassfish v3. Can any one point out what may cause such behavior?

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• How do you access the Source Error, Source File and Line Number of an exception to use in a custom e

  - by Iain Fraser

  Basically I want to take the following: And make it match the styling of the rest of the application. I am creating a custom error page in my C# based project and I want it to be able to show the same information that is displayed in the ASP.NET default error page. From fiddling with reflector I can see that this is generated through HttpException.GetHtmlErrorMessage() but when I try to use this in my exception it returns null.

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• I've caught an exception!! Now what?

  - by Jonesy

  Hi folks, I've started using try catch blocks (bit late i know!) but now im not sure what to do with the exception once i've caught it. What do people usually do here? -- Jonesy Try connection.Open() Dim sqlCmd As New SqlCommand("do some SQL", connection) Dim sqlDa As New SqlDataAdapter(sqlCmd) sqlDa.Fill(dt) Catch ex As SQLException ' ahhhh what to do now!!!? Finally connection.Close() End Try

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• Is there a way to make eclipse report a general "catch (Exception e)" as an error/warning (in java)?

  - by Rog

  I'm trying to encourage a best practice of not catching general exceptions in Java code. eg: try { ... } catch (Exception e) { // bad! ... } Is there a way to flag this as an error/warning in Eclipse? I know PMD picks this up, but I'd rather avoid integrating it into everyone's build environment at the moment.

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• How to change Exception message, "The application ... has stopped unexpectedly. Please try again lat

  - by ChaimKut

  Is there any way to modify the generic Android Exception message "The application ... has stopped unexpectedly. Please try again later.” to display something more meaningful to the user?

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• Is it possible to control Visual Studio exception handling from the debugged code itself?

  - by mark

  Dear ladies and sirs. I am wondering if it is possible to control the Visual Studio exception handling options from the code itself. For instance, I would like to turn off stopping on FCE for a certain piece of code, that generates many FCE, however, I would like it to be active for all the other code. Is it possible to do it from code? Something like this: visualStudio.DoNotStopOnFCE() try { // some code generating many FCE } catch {} visualStudio.StopOnFCE() Thanks.

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• Is it possible to catch out of memory exception in java?

  - by jy

  I'm developing a program that would require huge amount of memory, and I want to catch when out-of-memory exception happens. I had heard this is not possible to do, but curious if there is any development on this end.

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• Where to define exception classes, inside classes or on a higher level?

  - by rve

  Should exception classes be part of the class which may throw them or should they exist on a higher level? For example : class Test { public: class FooException: public ExceptionBase { }; void functionThrowingFooException(); }; or class FooException: public ExceptionBase { }; class Test { public: void functionThrowingFooException(); }; (functionThrowingFooException() is the only function to ever throw a FooException)

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• It&rsquo;s ok to throw System.Exception&hellip;

  - by Chris Skardon

  No. No it’s not. It’s not just me saying that, it’s the Microsoft guidelines: http://msdn.microsoft.com/en-us/library/ms229007.aspx  Do not throw System.Exception or System.SystemException. Also – as important: Do not catch System.Exception or System.SystemException in framework code, unless you intend to re-throw.. Throwing: Always, always try to pick the most specific exception type you can, if the parameter you have received in your method is null, throw an ArgumentNullException, value received greater than expected? ArgumentOutOfRangeException. For example: public void ArgChecker(int theInt, string theString) { if (theInt < 0) throw new ArgumentOutOfRangeException("theInt", theInt, "theInt needs to be greater than zero."); if (theString == null) throw new ArgumentNullException("theString"); if (theString.Length == 0) throw new ArgumentException("theString needs to have content.", "theString"); } Why do we want to do this? It’s a lot of extra code when compared with a simple: public void ArgChecker(int theInt, string theString) { if (theInt < 0 || string.IsNullOrWhiteSpace(theString)) throw new Exception("The parameters were invalid."); } It all comes down to a couple of things; the catching of the exceptions, and the information you are passing back to the calling code. Catching: Ok, so let’s go with introduction level Exception handling, taught by many-a-university: You do all your work in a try clause, and catch anything wrong in the catch clause. So this tends to give us code like this: try { /* All the shizzle */ } catch { /* Deal with errors */ } But of course, we can improve on that by catching the exception so we can report on it: try { } catch(Exception ex) { /* Log that 'ex' occurred? */ } Now we’re at the point where people tend to go: Brilliant, I’ve got exception handling nailed, what next??? and code gets littered with the catch(Exception ex) nastiness. Why is it nasty? Let’s imagine for a moment our code is throwing an ArgumentNullException which we’re catching in the catch block and logging. Ok, the log entry has been made, so we can debug the code right? We’ve got all the info… What about an OutOfMemoryException – what can we do with that? That’s right, not a lot, chances are you can’t even log it (you are out of memory after all), but you’ve caught it – and as such - have hidden it. So, as part of this, there are two things you can do one, is the rethrow method: try { /* code */ } catch (Exception ex) { //Log throw; } Note, it’s not catch (Exception ex) { throw ex; } as that will wipe all your important stack trace information. This does get your exception to continue, and is the only reason you would catch Exception (anywhere other than a global catch-all) in your code. The other preferred method is to catch the exceptions you can deal with. It may not matter that the string I’m passing in is null, and I can cope with it like this: try{ DoSomething(myString); } catch(ArgumentNullException){} And that’s fine, it means that any exceptions I can’t deal with (OutOfMemory for example) will be propagated out to other code that can deal with it. Of course, this is horribly messy, no one wants try / catch blocks everywhere and that’s why Microsoft added the ‘Try’ methods to the framework, and it’s a strategy we should continue. If I try: int i = (int) "one"; I will get an InvalidCastException which means I need the try / catch block, but I could mitigate this using the ‘TryParse’ method: int i; if(!Int32.TryParse("one", out i)) return; Similarly, in the ‘DoSomething’ example, it might be beneficial to have a ‘TryDoSomething’ that returns a boolean value indicating the success of continuing. Obviously this isn’t practical in every case, so use the ol’ common sense approach. Onwards Yer thanks Chris, I’m looking forward to writing tonnes of new code. Fear not, that is where helpers come into it… (but that’s the next post)

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• Throwing a C++ exception after an inline-asm jump

  - by SoapBox

  I have some odd self modifying code, but at the root of it is a pretty simple problem: I want to be able to execute a jmp (or a call) and then from that arbitrary point throw an exception and have it caught by the try/catch block that contained the jmp/call. But when I do this (in gcc 4.4.1 x86_64) the exception results in a terminate() as it would if the exception was thrown from outside of a try/catch. I don't really see how this is different than throwing an exception from inside of some far-flung library, yet it obviously is because it just doesn't work. How can I execute a jmp or call but still throw an exception back to the original try/catch? Why doesn't this try/catch continue to handle these exceptions as it would if the function was called normally? The code: #include <iostream> #include <stdexcept> using namespace std; void thrower() { cout << "Inside thrower" << endl; throw runtime_error("some exception"); } int main() { cout << "Top of main" << endl; try { asm volatile ( "jmp *%0" // same thing happens with a call instead of a jmp : : "r"((long)thrower) : ); } catch (exception &e) { cout << "Caught : " << e.what() << endl; } cout << "Bottom of main" << endl << endl; } The expected output: Top of main Inside thrower Caught : some exception Bottom of main The actual output: Top of main Inside thrower terminate called after throwing an instance of 'std::runtime_error' what(): some exception Aborted

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• Catching specific vs. generic exceptions in c#

  - by Scott Vercuski

  This question comes from a code analysis run against an object I've created. The analysis says that I should catch a more specific exception type than just the basic Exception. Do you find yourself using just catching the generic Exception or attempting to catch a specific Exception and defaulting to a generic Exception using multiple catch blocks? One of the code chunks in question is below: internal static bool ClearFlags(string connectionString, Guid ID) { bool returnValue = false; SqlConnection dbEngine = new SqlConnection(connectionString); SqlCommand dbCmd = new SqlCommand("ClearFlags", dbEngine); SqlDataAdapter dataAdapter = new SqlDataAdapter(dbCmd); dbCmd.CommandType = CommandType.StoredProcedure; try { dbCmd.Parameters.AddWithValue("@ID", ID.ToString()); dbEngine.Open(); dbCmd.ExecuteNonQuery(); dbEngine.Close(); returnValue = true; } catch (Exception ex) { ErrorHandler(ex); } return returnValue; } Thank you for your advice EDIT: Here is the warning from the code analysis Warning 351 CA1031 : Microsoft.Design : Modify 'ClearFlags(string, Guid)' to catch a more specific exception than 'Exception' or rethrow the exception

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• unknown exception error in php

  - by fayer

  i wanna catch all exceptions thrown in a script and then check if they have a error code 23000. if they don't i want to rethrow the exception. here is my code: function myException($exception) { /*** If it is a Doctrine Connection Mysql Duplication Exception ***/ if(get_class($exception) === 'Doctrine_Connection_Mysql_Exception' && $exception->getCode() === 23000) { echo "Duplicate entry"; } else { throw $exception; } } set_exception_handler('myException'); $contact = new Contact(); $contact->email = 'peter'; $contact->save(); but i get this error message and i dont know what it means: Fatal error: Exception thrown without a stack frame in Unknown on line 0 i want to be able to rethrow the original error message if it has not the error code 23000. even when i deleted the check errorcode i still get the same message: function myException($exception) { throw $exception; } set_exception_handler('myException'); $contact = new Contact(); $contact->email = 'peter'; $contact->save(); how could i solve this? thanks

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• Entity Framework Code-First, OData & Windows Phone Client

  - by Jon Galloway

  Entity Framework Code-First is the coolest thing since sliced bread, Windows  Phone is the hottest thing since Tickle-Me-Elmo and OData is just too great to ignore. As part of the Full Stack project, we wanted to put them together, which turns out to be pretty easy… once you know how.   EF Code-First CTP5 is available now and there should be very few breaking changes in the release edition, which is due early in 2011.  Note: EF Code-First evolved rapidly and many of the existing documents and blog posts which were written with earlier versions, may now be obsolete or at least misleading.   Code-First? With traditional Entity Framework you start with a database and from that you generate “entities” – classes that bridge between the relational database and your object oriented program. With Code-First (Magic-Unicorn) (see Hanselman’s write up and this later write up by Scott Guthrie) the Entity Framework looks at classes you created and says “if I had created these classes, the database would have to have looked like this…” and creates the database for you! By deriving your entity collections from DbSet and exposing them via a class that derives from DbContext, you "turn on" database backing for your POCO with a minimum of code and no hidden designer or configuration files. POCO == Plain Old CLR Objects Your entity objects can be used throughout your applications - in web applications, console applications, Silverlight and Windows Phone applications, etc. In our case, we'll want to read and update data from a Windows Phone client application, so we'll expose the entities through a DataService and hook the Windows Phone client application to that data via proxies.  Piece of Pie.  Easy as cake. The Demo Architecture To see this at work, we’ll create an ASP.NET/MVC application which will act as the host for our Data Service.  We’ll create an incredibly simple data layer using EF Code-First on top of SQLCE4 and we’ll expose the data in a WCF Data Service using the oData protocol.  Our Windows Phone 7 client will instantiate  the data context via a URI and load the data asynchronously. Setting up the Server project with MVC 3, EF Code First, and SQL CE 4 Create a new application of type ASP.NET MVC 3 and name it DeadSimpleServer.  We need to add the latest SQLCE4 and Entity Framework Code First CTP's to our project. Fortunately, NuGet makes that really easy. Open the Package Manager Console (View / Other Windows / Package Manager Console) and type in "Install-Package EFCodeFirst.SqlServerCompact" at the PM> command prompt. Since NuGet handles dependencies for you, you'll see that it installs everything you need to use Entity Framework Code First in your project. PM> install-package EFCodeFirst.SqlServerCompact 'SQLCE (= 4.0.8435.1)' not installed. Attempting to retrieve dependency from source... Done 'EFCodeFirst (= 0.8)' not installed. Attempting to retrieve dependency from source... Done 'WebActivator (= 1.0.0.0)' not installed. Attempting to retrieve dependency from source... Done You are downloading SQLCE from Microsoft, the license agreement to which is available at http://173.203.67.148/licenses/SQLCE/EULA_ENU.rtf. Check the package for additional dependencies, which may come with their own license agreement(s). Your use of the package and dependencies constitutes your acceptance of their license agreements. If you do not accept the license agreement(s), then delete the relevant components from your device. Successfully installed 'SQLCE 4.0.8435.1' You are downloading EFCodeFirst from Microsoft, the license agreement to which is available at http://go.microsoft.com/fwlink/?LinkID=206497. Check the package for additional dependencies, which may come with their own license agreement(s). Your use of the package and dependencies constitutes your acceptance of their license agreements. If you do not accept the license agreement(s), then delete the relevant components from your device. Successfully installed 'EFCodeFirst 0.8' Successfully installed 'WebActivator 1.0.0.0' You are downloading EFCodeFirst.SqlServerCompact from Microsoft, the license agreement to which is available at http://173.203.67.148/licenses/SQLCE/EULA_ENU.rtf. Check the package for additional dependencies, which may come with their own license agreement(s). Your use of the package and dependencies constitutes your acceptance of their license agreements. If you do not accept the license agreement(s), then delete the relevant components from your device. Successfully installed 'EFCodeFirst.SqlServerCompact 0.8' Successfully added 'SQLCE 4.0.8435.1' to EfCodeFirst-CTP5 Successfully added 'EFCodeFirst 0.8' to EfCodeFirst-CTP5 Successfully added 'WebActivator 1.0.0.0' to EfCodeFirst-CTP5 Successfully added 'EFCodeFirst.SqlServerCompact 0.8' to EfCodeFirst-CTP5 Note: We're using SQLCE 4 with Entity Framework here because they work really well together from a development scenario, but you can of course use Entity Framework Code First with other databases supported by Entity framework. Creating The Model using EF Code First Now we can create our model class. Right-click the Models folder and select Add/Class. Name the Class Person.cs and add the following code: using System.Data.Entity; namespace DeadSimpleServer.Models { public class Person { public int ID { get; set; } public string Name { get; set; } } public class PersonContext : DbContext { public DbSet<Person> People { get; set; } } } Notice that the entity class Person has no special interfaces or base class. There's nothing special needed to make it work - it's just a POCO. The context we'll use to access the entities in the application is called PersonContext, but you could name it anything you wanted. The important thing is that it inherits DbContext and contains one or more DbSet which holds our entity collections. Adding Seed Data We need some testing data to expose from our service. The simplest way to get that into our database is to modify the CreateCeDatabaseIfNotExists class in AppStart_SQLCEEntityFramework.cs by adding some seed data to the Seed method: protected virtual void Seed( TContext context ) { var personContext = context as PersonContext; personContext.People.Add( new Person { ID = 1, Name = "George Washington" } ); personContext.People.Add( new Person { ID = 2, Name = "John Adams" } ); personContext.People.Add( new Person { ID = 3, Name = "Thomas Jefferson" } ); personContext.SaveChanges(); } The CreateCeDatabaseIfNotExists class name is pretty self-explanatory - when our DbContext is accessed and the database isn't found, a new one will be created and populated with the data in the Seed method. There's one more step to make that work - we need to uncomment a line in the Start method at the top of of the AppStart_SQLCEEntityFramework class and set the context name, as shown here, public static class AppStart_SQLCEEntityFramework { public static void Start() { DbDatabase.DefaultConnectionFactory = new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0"); // Sets the default database initialization code for working with Sql Server Compact databases // Uncomment this line and replace CONTEXT_NAME with the name of your DbContext if you are // using your DbContext to create and manage your database DbDatabase.SetInitializer(new CreateCeDatabaseIfNotExists<PersonContext>()); } } Now our database and entity framework are set up, so we can expose data via WCF Data Services. Note: This is a bare-bones implementation with no administration screens. If you'd like to see how those are added, check out The Full Stack screencast series. Creating the oData Service using WCF Data Services Add a new WCF Data Service to the project (right-click the project / Add New Item / Web / WCF Data Service). We’ll be exposing all the data as read/write.  Remember to reconfigure to control and minimize access as appropriate for your own application. Open the code behind for your service. In our case, the service was called PersonTestDataService.svc so the code behind class file is PersonTestDataService.svc.cs. using System.Data.Services; using System.Data.Services.Common; using System.ServiceModel; using DeadSimpleServer.Models; namespace DeadSimpleServer { [ServiceBehavior( IncludeExceptionDetailInFaults = true )] public class PersonTestDataService : DataService<PersonContext> { // This method is called only once to initialize service-wide policies. public static void InitializeService( DataServiceConfiguration config ) { config.SetEntitySetAccessRule( "*", EntitySetRights.All ); config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2; config.UseVerboseErrors = true; } } } We're enabling a few additional settings to make it easier to debug if you run into trouble. The ServiceBehavior attribute is set to include exception details in faults, and we're using verbose errors. You can remove both of these when your service is working, as your public production service shouldn't be revealing exception information. You can view the output of the service by running the application and browsing to http://localhost:[portnumber]/PersonTestDataService.svc/: <service xml:base="http://localhost:49786/PersonTestDataService.svc/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns="http://www.w3.org/2007/app"> <workspace> <atom:title>Default</atom:title> <collection href="People"> <atom:title>People</atom:title> </collection> </workspace> </service> This indicates that the service exposes one collection, which is accessible by browsing to http://localhost:[portnumber]/PersonTestDataService.svc/People <?xml version="1.0" encoding="iso-8859-1" standalone="yes"?> <feed xml:base=http://localhost:49786/PersonTestDataService.svc/ xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom"> <title type="text">People</title> <id>http://localhost:49786/PersonTestDataService.svc/People</id> <updated>2010-12-29T01:01:50Z</updated> <link rel="self" title="People" href="People" /> <entry> <id>http://localhost:49786/PersonTestDataService.svc/People(1)</id> <title type="text"></title> <updated>2010-12-29T01:01:50Z</updated> <author> <name /> </author> <link rel="edit" title="Person" href="People(1)" /> <category term="DeadSimpleServer.Models.Person" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" /> <content type="application/xml"> <m:properties> <d:ID m:type="Edm.Int32">1</d:ID> <d:Name>George Washington</d:Name> </m:properties> </content> </entry> <entry> ... </entry> </feed> Let's recap what we've done so far. But enough with services and XML - let's get this into our Windows Phone client application. Creating the DataServiceContext for the Client Use the latest DataSvcUtil.exe from http://odata.codeplex.com. As of today, that's in this download: http://odata.codeplex.com/releases/view/54698 You need to run it with a few options: /uri - This will point to the service URI. In this case, it's http://localhost:59342/PersonTestDataService.svc  Pick up the port number from your running server (e.g., the server formerly known as Cassini). /out - This is the DataServiceContext class that will be generated. You can name it whatever you'd like. /Version - should be set to 2.0 /DataServiceCollection - Include this flag to generate collections derived from the DataServiceCollection base, which brings in all the ObservableCollection goodness that handles your INotifyPropertyChanged events for you. Here's the console session from when we ran it: <ListBox x:Name="MainListBox" Margin="0,0,-12,0" ItemsSource="{Binding}" SelectionChanged="MainListBox_SelectionChanged"> Next, to keep things simple, change the Binding on the two TextBlocks within the DataTemplate to Name and ID, <ListBox x:Name="MainListBox" Margin="0,0,-12,0" ItemsSource="{Binding}" SelectionChanged="MainListBox_SelectionChanged"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Margin="0,0,0,17" Width="432"> <TextBlock Text="{Binding Name}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" /> <TextBlock Text="{Binding ID}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextSubtleStyle}" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> Getting The Context In the code-behind you’ll first declare a member variable to hold the context from the Entity Framework. This is named using convention over configuration. The db type is Person and the context is of type PersonContext, You initialize it by providing the URI, in this case using the URL obtained from the Cassini web server, PersonContext context = new PersonContext( new Uri( "http://localhost:49786/PersonTestDataService.svc/" ) ); Create a second member variable of type DataServiceCollection<Person> but do not initialize it, DataServiceCollection<Person> people; In the constructor you’ll initialize the DataServiceCollection using the PersonContext, public MainPage() { InitializeComponent(); people = new DataServiceCollection<Person>( context ); Finally, you’ll load the people collection using the LoadAsync method, passing in the fully specified URI for the People collection in the web service, people.LoadAsync( new Uri( "http://localhost:49786/PersonTestDataService.svc/People" ) ); Note that this method runs asynchronously and when it is finished the people  collection is already populated. Thus, since we didn’t need or want to override any of the behavior we don’t implement the LoadCompleted. You can use the LoadCompleted event if you need to do any other UI updates, but you don't need to. The final code is as shown below: using System; using System.Data.Services.Client; using System.Windows; using System.Windows.Controls; using DeadSimpleServer.Models; using Microsoft.Phone.Controls; namespace WindowsPhoneODataTest { public partial class MainPage : PhoneApplicationPage { PersonContext context = new PersonContext( new Uri( "http://localhost:49786/PersonTestDataService.svc/" ) ); DataServiceCollection<Person> people; // Constructor public MainPage() { InitializeComponent(); // Set the data context of the listbox control to the sample data // DataContext = App.ViewModel; people = new DataServiceCollection<Person>( context ); people.LoadAsync( new Uri( "http://localhost:49786/PersonTestDataService.svc/People" ) ); DataContext = people; this.Loaded += new RoutedEventHandler( MainPage_Loaded ); } // Handle selection changed on ListBox private void MainListBox_SelectionChanged( object sender, SelectionChangedEventArgs e ) { // If selected index is -1 (no selection) do nothing if ( MainListBox.SelectedIndex == -1 ) return; // Navigate to the new page NavigationService.Navigate( new Uri( "/DetailsPage.xaml?selectedItem=" + MainListBox.SelectedIndex, UriKind.Relative ) ); // Reset selected index to -1 (no selection) MainListBox.SelectedIndex = -1; } // Load data for the ViewModel Items private void MainPage_Loaded( object sender, RoutedEventArgs e ) { if ( !App.ViewModel.IsDataLoaded ) { App.ViewModel.LoadData(); } } } } With people populated we can set it as the DataContext and run the application; you’ll find that the Name and ID are displayed in the list on the Mainpage. Here's how the pieces in the client fit together: Complete source code available here

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• Error internal server error exception Search Core Result webpart

  - by Patrick Olurotimi Ige

  I migrated a WSS v3 to Sharepoint Foundation 2010 and all went ok apart from some few errors. I then tried installing a Sharepoint 2010 express search which went ok. But after trying to add  the Search Core Result webpart  to a search center i got the  error : internal server error exception I found a solution here And you can download the hofix here Hope this helps

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• Class-Level Model Validation with EF Code First and ASP.NET MVC 3

  - by ScottGu

  Earlier this week the data team released the CTP5 build of the new Entity Framework Code-First library.  In my blog post a few days ago I talked about a few of the improvements introduced with the new CTP5 build.  Automatic support for enforcing DataAnnotation validation attributes on models was one of the improvements I discussed.  It provides a pretty easy way to enable property-level validation logic within your model layer. You can apply validation attributes like [Required], [Range], and [RegularExpression] – all of which are built-into .NET 4 – to your model classes in order to enforce that the model properties are valid before they are persisted to a database.  You can also create your own custom validation attributes (like this cool [CreditCard] validator) and have them be automatically enforced by EF Code First as well.  This provides a really easy way to validate property values on your models.  I showed some code samples of this in action in my previous post. Class-Level Model Validation using IValidatableObject DataAnnotation attributes provides an easy way to validate individual property values on your model classes.  Several people have asked - “Does EF Code First also support a way to implement class-level validation methods on model objects, for validation rules than need to span multiple property values?”  It does – and one easy way you can enable this is by implementing the IValidatableObject interface on your model classes. IValidatableObject.Validate() Method Below is an example of using the IValidatableObject interface (which is built-into .NET 4 within the System.ComponentModel.DataAnnotations namespace) to implement two custom validation rules on a Product model class.  The two rules ensure that: New units can’t be ordered if the Product is in a discontinued state New units can’t be ordered if there are already more than 100 units in stock We will enforce these business rules by implementing the IValidatableObject interface on our Product class, and by implementing its Validate() method like so: The IValidatableObject.Validate() method can apply validation rules that span across multiple properties, and can yield back multiple validation errors. Each ValidationResult returned can supply both an error message as well as an optional list of property names that caused the violation (which is useful when displaying error messages within UI). Automatic Validation Enforcement EF Code-First (starting with CTP5) now automatically invokes the Validate() method when a model object that implements the IValidatableObject interface is saved.  You do not need to write any code to cause this to happen – this support is now enabled by default. This new support means that the below code – which violates one of our above business rules – will automatically throw an exception (and abort the transaction) when we call the “SaveChanges()” method on our Northwind DbContext: In addition to reactively handling validation exceptions, EF Code First also allows you to proactively check for validation errors.  Starting with CTP5, you can call the “GetValidationErrors()” method on the DbContext base class to retrieve a list of validation errors within the model objects you are working with.  GetValidationErrors() will return a list of all validation errors – regardless of whether they are generated via DataAnnotation attributes or by an IValidatableObject.Validate() implementation.  Below is an example of proactively using the GetValidationErrors() method to check (and handle) errors before trying to call SaveChanges(): ASP.NET MVC 3 and IValidatableObject ASP.NET MVC 2 included support for automatically honoring and enforcing DataAnnotation attributes on model objects that are used with ASP.NET MVC’s model binding infrastructure.  ASP.NET MVC 3 goes further and also honors the IValidatableObject interface.  This combined support for model validation makes it easy to display appropriate error messages within forms when validation errors occur.  To see this in action, let’s consider a simple Create form that allows users to create a new Product: We can implement the above Create functionality using a ProductsController class that has two “Create” action methods like below: The first Create() method implements a version of the /Products/Create URL that handles HTTP-GET requests - and displays the HTML form to fill-out.  The second Create() method implements a version of the /Products/Create URL that handles HTTP-POST requests - and which takes the posted form data, ensures that is is valid, and if it is valid saves it in the database.  If there are validation issues it redisplays the form with the posted values.  The razor view template of our “Create” view (which renders the form) looks like below: One of the nice things about the above Controller + View implementation is that we did not write any validation logic within it.  The validation logic and business rules are instead implemented entirely within our model layer, and the ProductsController simply checks whether it is valid (by calling the ModelState.IsValid helper method) to determine whether to try and save the changes or redisplay the form with errors. The Html.ValidationMessageFor() helper method calls within our view simply display the error messages our Product model’s DataAnnotations and IValidatableObject.Validate() method returned.  We can see the above scenario in action by filling out invalid data within the form and attempting to submit it: Notice above how when we hit the “Create” button we got an error message.  This was because we ticked the “Discontinued” checkbox while also entering a value for the UnitsOnOrder (and so violated one of our business rules).  You might ask – how did ASP.NET MVC know to highlight and display the error message next to the UnitsOnOrder textbox?  It did this because ASP.NET MVC 3 now honors the IValidatableObject interface when performing model binding, and will retrieve the error messages from validation failures with it. The business rule within our Product model class indicated that the “UnitsOnOrder” property should be highlighted when the business rule we hit was violated: Our Html.ValidationMessageFor() helper method knew to display the business rule error message (next to the UnitsOnOrder edit box) because of the above property name hint we supplied: Keeping things DRY ASP.NET MVC and EF Code First enables you to keep your validation and business rules in one place (within your model layer), and avoid having it creep into your Controllers and Views.  Keeping the validation logic in the model layer helps ensure that you do not duplicate validation/business logic as you add more Controllers and Views to your application.  It allows you to quickly change your business rules/validation logic in one single place (within your model layer) – and have all controllers/views across your application immediately reflect it.  This help keep your application code clean and easily maintainable, and makes it much easier to evolve and update your application in the future. Summary EF Code First (starting with CTP5) now has built-in support for both DataAnnotations and the IValidatableObject interface.  This allows you to easily add validation and business rules to your models, and have EF automatically ensure that they are enforced anytime someone tries to persist changes of them to a database.  ASP.NET MVC 3 also now supports both DataAnnotations and IValidatableObject as well, which makes it even easier to use them with your EF Code First model layer – and then have the controllers/views within your web layer automatically honor and support them as well.  This makes it easy to build clean and highly maintainable applications. You don’t have to use DataAnnotations or IValidatableObject to perform your validation/business logic.  You can always roll your own custom validation architecture and/or use other more advanced validation frameworks/patterns if you want.  But for a lot of applications this built-in support will probably be sufficient – and provide a highly productive way to build solutions. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• LINQ: Single vs. First

  - by Paulo Morgado

  I’ve witnessed and been involved in several discussions around the correctness or usefulness of the Single method in the LINQ API. The most common argument is that you are querying for the first element on the result set and an exception will be thrown if there’s more than one element. The First method should be used instead, because it doesn’t throw if the result set has more than one item. Although the documentation for Single states that it returns a single, specific element of a sequence of values, it actually returns THE single, specific element of a sequence of ONE value. One you use the Single method in your code you are asserting that your query will result in a scalar result instead of a result set of arbitrary length. On the other hand, the documentation for First states that it returns the first element of a sequence of arbitrary length. Imagine you want to catch a taxi. You go the the taxi line and catch the FIRST one, no matter how many are there. On the other hand, if you go the the parking lot to get your car, you want the SINGLE one specific car that’s yours. If your “query” “returns” more than one car, it’s an exception. Either because it “returned” not only your car or you happen to have more than one car in that parking lot. In either case, you can only drive one car at once and you’ll need to refine your “query”.

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