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• C# - Cannot implicitly convert type List<Product> to List<IProduct>

  - by Keith Barrows

  I have a project with all my Interface definitions: RivWorks.Interfaces I have a project where I define concrete implmentations: RivWorks.DTO I've done this hundreds of times before but for some reason I am getting this error now: Cannot implicitly convert type 'System.Collections.Generic.List<RivWorks.DTO.Product>' to 'System.Collections.Generic.List<RivWorks.Interfaces.DataContracts.IProduct>' Interface definition (shortened): namespace RivWorks.Interfaces.DataContracts { public interface IProduct { [XmlElement] [DataMember(Name = "ID", Order = 0)] Guid ProductID { get; set; } [XmlElement] [DataMember(Name = "altID", Order = 1)] long alternateProductID { get; set; } [XmlElement] [DataMember(Name = "CompanyId", Order = 2)] Guid CompanyId { get; set; } ... } } Concrete class definition (shortened): namespace RivWorks.DTO { [DataContract(Name = "Product", Namespace = "http://rivworks.com/DataContracts/2009/01/15")] public class Product : IProduct { #region Constructors public Product() { } public Product(Guid ProductID) { Initialize(ProductID); } public Product(string SKU, Guid CompanyID) { using (RivEntities _dbRiv = new RivWorksStore(stores.RivConnString).NegotiationEntities()) { model.Product rivProduct = _dbRiv.Product.Where(a => a.SKU == SKU && a.Company.CompanyId == CompanyID).FirstOrDefault(); if (rivProduct != null) Initialize(rivProduct.ProductId); } } #endregion #region Private Methods private void Initialize(Guid ProductID) { using (RivEntities _dbRiv = new RivWorksStore(stores.RivConnString).NegotiationEntities()) { var localProduct = _dbRiv.Product.Include("Company").Where(a => a.ProductId == ProductID).FirstOrDefault(); if (localProduct != null) { var companyDetails = _dbRiv.vwCompanyDetails.Where(a => a.CompanyId == localProduct.Company.CompanyId).FirstOrDefault(); if (companyDetails != null) { if (localProduct.alternateProductID != null && localProduct.alternateProductID > 0) { using (FeedsEntities _dbFeed = new FeedStoreReadOnly(stores.FeedConnString).ReadOnlyEntities()) { var feedProduct = _dbFeed.AutoWithImage.Where(a => a.ClientID == companyDetails.ClientID && a.AutoID == localProduct.alternateProductID).FirstOrDefault(); if (companyDetails.useZeroGspPath.Value || feedProduct.GuaranteedSalePrice > 0) // kab: 2010.04.07 - new rules... PopulateProduct(feedProduct, localProduct, companyDetails); } } else { if (companyDetails.useZeroGspPath.Value || localProduct.LowestPrice > 0) // kab: 2010.04.07 - new rules... PopulateProduct(localProduct, companyDetails); } } } } } private void PopulateProduct(RivWorks.Model.Entities.Product product, RivWorks.Model.Entities.vwCompanyDetails RivCompany) { this.ProductID = product.ProductId; if (product.alternateProductID != null) this.alternateProductID = product.alternateProductID.Value; this.BackgroundColor = product.BackgroundColor; ... } private void PopulateProduct(RivWorks.Model.Entities.AutoWithImage feedProduct, RivWorks.Model.Entities.Product rivProduct, RivWorks.Model.Entities.vwCompanyDetails RivCompany) { this.alternateProductID = feedProduct.AutoID; this.BackgroundColor = Helpers.Product.GetCorrectValue(RivCompany.defaultBackgroundColor, rivProduct.BackgroundColor); ... } #endregion #region IProduct Members public Guid ProductID { get; set; } public long alternateProductID { get; set; } public Guid CompanyId { get; set; } ... #endregion } } In another class I have: using dto = RivWorks.DTO; using contracts = RivWorks.Interfaces.DataContracts; ... public static List<contracts.IProduct> Get(Guid companyID) { List<contracts.IProduct> myList = new List<dto.Product>(); ... Any ideas why this might be happening? (And I am sure it is something trivially simple!)

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• Templated function with two type parameters fails compile when used with an error-checking macro

  - by SirPentor

  Because someone in our group hates exceptions (let's not discuss that here), we tend to use error-checking macros in our C++ projects. I have encountered an odd compilation failure when using a templated function with two type parameters. There are a few errors (below), but I think the root cause is a warning: warning C4002: too many actual parameters for macro 'BOOL_CHECK_BOOL_RETURN' Probably best explained in code: #include "stdafx.h" template<class A, class B> bool DoubleTemplated(B & value) { return true; } template<class A> bool SingleTemplated(A & value) { return true; } bool NotTemplated(bool & value) { return true; } #define BOOL_CHECK_BOOL_RETURN(expr) \ do \ { \ bool __b = (expr); \ if (!__b) \ { \ return false; \ } \ } while (false) \ bool call() { bool thing = true; // BOOL_CHECK_BOOL_RETURN(DoubleTemplated<int, bool>(thing)); // Above line doesn't compile. BOOL_CHECK_BOOL_RETURN((DoubleTemplated<int, bool>(thing))); // Above line compiles just fine. bool temp = DoubleTemplated<int, bool>(thing); // Above line compiles just fine. BOOL_CHECK_BOOL_RETURN(SingleTemplated<bool>(thing)); BOOL_CHECK_BOOL_RETURN(NotTemplated(thing)); return true; } int _tmain(int argc, _TCHAR* argv[]) { call(); return 0; } Here are the errors, when the offending line is not commented out: 1>------ Build started: Project: test, Configuration: Debug Win32 ------ 1>Compiling... 1>test.cpp 1>c:\junk\temp\test\test\test.cpp(38) : warning C4002: too many actual parameters for macro 'BOOL_CHECK_BOOL_RETURN' 1>c:\junk\temp\test\test\test.cpp(38) : error C2143: syntax error : missing ',' before ')' 1>c:\junk\temp\test\test\test.cpp(38) : error C2143: syntax error : missing ';' before '{' 1>c:\junk\temp\test\test\test.cpp(41) : error C2143: syntax error : missing ';' before '{' 1>c:\junk\temp\test\test\test.cpp(48) : error C2143: syntax error : missing ';' before '{' 1>c:\junk\temp\test\test\test.cpp(49) : error C2143: syntax error : missing ';' before '{' 1>c:\junk\temp\test\test\test.cpp(52) : error C2143: syntax error : missing ';' before '}' 1>c:\junk\temp\test\test\test.cpp(54) : error C2065: 'argv' : undeclared identifier 1>c:\junk\temp\test\test\test.cpp(54) : error C2059: syntax error : ']' 1>c:\junk\temp\test\test\test.cpp(55) : error C2143: syntax error : missing ';' before '{' 1>c:\junk\temp\test\test\test.cpp(58) : error C2143: syntax error : missing ';' before '}' 1>c:\junk\temp\test\test\test.cpp(60) : error C2143: syntax error : missing ';' before '}' 1>c:\junk\temp\test\test\test.cpp(60) : fatal error C1004: unexpected end-of-file found 1>Build log was saved at "file://c:\junk\temp\test\test\Debug\BuildLog.htm" 1>test - 12 error(s), 1 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Any ideas? Thanks!

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• varchar(255) to varchar(MAX)

  - by JD

  Is it possible to change a column type in a MS SQL 2008 database from varchar(255) to varchar(MAX) without having to drop the table and recreate? SQL Server Management Studio throws me an error every time I try to do it using that - but to save myself a headache would be nice to know if I can change the type without having to DROP and CREATE. Thanks

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• Can LINQ-to-SQL omit unspecified columns on insert so a database default value is used?

  - by Todd Ropog

  I have a non-nullable database column which has a default value set. When inserting a row, sometimes a value is specified for the column, sometimes one is not. This works fine in TSQL when the column is omitted. For example, given the following table: CREATE TABLE [dbo].[Table1]( [id] [int] IDENTITY(1,1) NOT NULL, [col1] [nvarchar](50) NOT NULL, [col2] [nvarchar](50) NULL, CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED ([id] ASC) ) GO ALTER TABLE [dbo].[Table1] ADD CONSTRAINT [DF_Table1_col1] DEFAULT ('DB default') FOR [col1] The following two statements will work: INSERT INTO Table1 (col1, col2) VALUES ('test value', '') INSERT INTO Table1 (col2) VALUES ('') In the second statement, the default value is used for col1. The problem I have is when using LINQ-to-SQL (L2S) with a table like this. I want to produce the same behavior, but I can't figure out how to make L2S do that. I want to be able to run the following code and have the first row get the value I specify and the second row get the default value from the database: var context = new DataClasses1DataContext(); var row1 = new Table1 { col1 = "test value", col2 = "" }; context.Table1s.InsertOnSubmit(row1); context.SubmitChanges(); var row2 = new Table1 { col2 = "" }; context.Table1s.InsertOnSubmit(row2); context.SubmitChanges(); If the Auto Generated Value property of col1 is False, the first row is created as desired, but the second row fails with a null error on col1. If Auto Generated Value is True, both rows are created with the default value from the database. I've tried various combinations of Auto Generated Value, Auto-Sync and Nullable, but nothing I've tried gives the behavior I want. L2S does not omit the column from the insert statement when no value is specified. Instead it does something like this: INSERT INTO Table1 (col1, col2) VALUES (null, '') ...which of course causes a null error on col1. Is there some way to get L2S to omit a column from the insert statement if no value is given? Or is there some other way to get the behavior I want? I need the default value at the database level because not all row inserts are done via L2S, and in some cases the default value is a little more complex than a hard coded value (e.g. creating the default based on another field) so I'd rather avoid duplicating that logic.

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• .NET Settings File Available Types

  - by Mashmagar

  When modifying a .NET settings file, I'm given a choice of types for a setting. However, not all of the types accessible by my project appear, even in the 'Browse' window. What determines if a type can be used for a setting file setting? I have a type I created that I would like to be able to save, and I want to know what I need to change about it to use it in a settings file. (VS 2008 - .Net 3.5)

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• How do you send a HEAD HTTP request in Python?

  - by fuentesjr

  So what I'm trying to do here is get the headers of a given URL so I can determine the mime-type. I want to be able to see if http://somedomain/foo/ will return an html document or a jpg image for example. Thus, I need to figure out how to send a HEAD request so that I can read the mime-type without having to download the content. Does anyone know of an easy way of doing this?

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• How to tell Subversion to display binary files using an external program?

  - by lamcro

  I have some code which, like java, is stored in a binary format, and I have the applications to display and modify this code setup in the Subversion's config file. But when I run svn diff for these file, Subversion prevents me =================================================================== Cannot display: file marked as a binary type. svn:mime-type = application/octet-stream I can still view them, but only with the --force argument Since all the files in the repository are of this binary code, how can I permanently force subversion to open the files for diff or edit mode?

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• string <-> int/float conversion pain in .net winform

  - by Benny

  the Text property of control on winform is always string type, so if i wanna expose property of other type for custom control, i have to do the conversion as following, if i have dozens of properties to expose, it will be such pain for me. public int ImageGroupLength { get { return int.Parse(this.imageGroupLength.Text); } set { this.imageGroupLength.Text = value.ToString(); } } so, is there any elegant way to do the conversion?

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• Selecting a date value from a dynamically generated listbox.

  - by ziggy

  Hi All, I have a listbox whose values are generated dynamically. The list box contains months and years and when generated looks like this. <select name="arr_dtm_mon_year" tabindex="150" class="input"> <option value=""></option> <option value="NOV 09">Nov 09</option> <option value="DEC 09">Dec 09</option> <option value="JAN 10">Jan 10</option> <option value="FEB 10">Feb 10</option> <option value="MAR 10">Mar 10</option> <option value="APR 10">Apr 10</option> <option value="MAY 10">May 10</option> <option value="JUN 10" selected>Jun 10</option> <option value="JUL 10">Jul 10</option> <option value="AUG 10">Aug 10</option> <option value="SEP 10">Sep 10</option> <option value="OCT 10">Oct 10</option> </select> The element in the listbox that is by default selected is the current month. When i use selenium IDE to select from this listbox it works fine. Here are example commands i use to select from the listbox. <tr> <td>select</td> <td>arr_dtm_mon_year</td> <td>label=Oct 10</td> </tr> <tr> <td>select</td> <td>arr_dtm_mon_year</td> <td>label=May 10</td> </tr> Now the problem i have is the values in the listbox is dynamically generated. In the above example i selected the option for "May 10". The values that are generated is a list of all previous six months and a list of all future six months. This basically means that if i rerun the test 6 months from now "May 10" will not be available from the list. Is it possible to select the value dynamically. For example can i first calculate the current month and select the value with that is current month + 1 (i.e. next month). And also how can i build the value to be selected after i have determined what the next month is. Any help will be greatly appreciated.

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• Getting the Assembly Qualified Name of a class in Visual Studio

  - by Alex Marshall

  Hello, I'm writing a customized reflective library for some specialized custom domain logic, and that library is going to use XML configuration files that will dynamically resolve System.Type objects at runtime. However, when writing the XML configuration files, it's a bit of a pain to write the types because they need to be fully qualified assembly names for Type.GetType() to resolve them. Is there a way to find out the AssemblyQualifiedName of an object in Visual Studio without resorting to writing a program to print them out to a file or standard out or anything like that ?

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• Manage views for content types (or add a view to multiple lists)

  - by Janis Veinbergs

  I'm surprised that I cannot find on the net a solution where I could manage views for content types. Do I really have to visit each task list with my browser to add/modify a view? Is there any solutions available that would allow me to just define a view for content type and thus make this view available on all lists where content type is?

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• Flash object wont load inside the application but loads in separated file.

  - by Taverneiro

  I have a Flash object that loads fine in a static sample HTML but doesnt inside the application. I saw something interesting in firebug. When the page loads the object is loaded two times. In the first one I get a Partial Response status but the content-type of the package is right. In the second time the whole package is transfered but the content-type is wrong! I am using apache 2.2.14.

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• Error while conversion of string to datetime

  - by aswathi

  The conversion of a char data type to a DateTime data type resulted in an out-of-range DateTime value. The statement has been terminated. Please give me most possible answers ALTER PROCEDURE [dbo].[attendance_updatebyemployee_id] @Employee_id int, @AtDate datetime, @FNLogged bit, @ANLogged bit, @LogTime varchar(10), @LogOuttime varchar(10) AS BEGIN SET NOCOUNT ON; update Mst_Attendance set FNLogged=@FNLogged, ANLogged=@ANLogged,LogTime=@LogTime,LogOuttime=@LogOuttime where EmployeeId=@Employee_id and Atdate= @AtDate END

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• C# underlying types of enums

  - by Marlon

  What is the point of having enum SomeEnum : byte // <---- { SomeValue = 0x01, ... } when you have to make a cast just to assign it to the same type of variable as the enums underlying type? byte b = (byte)SomeEnum.SomeValue;

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• How can I get the correct headers automatically given a filetype in PHP?

  - by incrediman

  A few times I've run into situations where I'd like to be able to include a file using PHP, and depending on the included filetype, output the appropriate headers. In the past I've just done this manually by switch/casing the extension type with the appropriate content-type headers. However what I'm wondering now is if there's a function like get_header($filename) or maybe get_contenttype($extension) For example if I wanted to route all requests for media through a php file, I could use that function to output the correct headers.

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• When is it important to have a public parameterless constructor in C#?

  - by raven

  I'm trying to understand the constraints on generic type parameters in C#. What is the purpose of the where T : new() constraint? Why would you need to insist that the type argument have a public parameterless constructor?

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• Unable to boot Windows 7 after installing Ubuntu

  - by Devendra

  I have Windows 7 on my machine and then installed Ubuntu 12.04 using a live CD. I can see both Windows 7 and Ubuntu in the grub menu, but when I select Windows 7 it shows a black screen for about 2 seconds and the returns to the Grub menu. But if I select Ubuntu it's working fine. This is the contents of the boot-repair log: Boot Info Script 0.61.full + Boot-Repair extra info [Boot-Info November 20th 2012] ============================= Boot Info Summary: =============================== => Grub2 (v2.00) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for (,msdos6)/boot/grub. sda1: __________________________________________________________________________ File system: ntfs Boot sector type: Grub2 (v1.99-2.00) Boot sector info: Grub2 (v2.00) is installed in the boot sector of sda1 and looks at sector 388911128 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for (,msdos6)/boot/grub. No errors found in the Boot Parameter Block. Operating System: Windows 7 Boot files: /bootmgr /Boot/BCD /Windows/System32/winload.exe sda2: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: sda3: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: sda4: __________________________________________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: sda5: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: According to the info in the boot sector, sda5 starts at sector 2048. Operating System: Boot files: sda6: __________________________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 12.10 Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/i386-pc/core.img sda7: __________________________________________________________________________ File system: swap Boot sector type: - Boot sector info: ============================ Drive/Partition Info: ============================= Drive: sda _____________________________________________________________________ Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 206,848 146,802,687 146,595,840 7 NTFS / exFAT / HPFS /dev/sda2 147,007,488 293,623,807 146,616,320 7 NTFS / exFAT / HPFS /dev/sda3 293,623,808 332,820,613 39,196,806 7 NTFS / exFAT / HPFS /dev/sda4 332,822,526 1,465,145,343 1,132,322,818 f W95 Extended (LBA) /dev/sda5 461,342,720 1,465,145,343 1,003,802,624 7 NTFS / exFAT / HPFS /dev/sda6 332,822,528 453,171,199 120,348,672 83 Linux /dev/sda7 453,173,248 461,338,623 8,165,376 82 Linux swap / Solaris "blkid" output: ________________________________________________________________ Device UUID TYPE LABEL /dev/sda1 F6AE2C13AE2BCB47 ntfs /dev/sda2 DC2273012272DFC6 ntfs /dev/sda3 1E76E43376E40D79 ntfs New Volume /dev/sda5 5ED60ACDD60AA57D ntfs /dev/sda6 9e70fd16-b48b-4f88-adcf-e443aef83124 ext4 /dev/sda7 52f3dd94-6be7-4a7b-a3ae-f43eb8810483 swap ================================ Mount points: ================================= Device Mount_Point Type Options /dev/sda6 / ext4 (rw,errors=remount-ro) =========================== sda6/boot/grub/grub.cfg: =========================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=auto load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_IN insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=10 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "${linux_gfx_mode}" != "text" ]; then load_video; fi menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash $vt_handoff initrd /boot/initrd.img-3.5.0-17-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-9e70fd16-b48b-4f88-adcf-e443aef83124' { menuentry 'Ubuntu, with Linux 3.5.0-17-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-advanced-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } menuentry 'Ubuntu, with Linux 3.5.0-17-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-recovery-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry 'Windows 7 (loader) (on /dev/sda1)' --class windows --class os $menuentry_id_option 'osprober-chain-F6AE2C13AE2BCB47' { insmod part_msdos insmod ntfs set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 F6AE2C13AE2BCB47 else search --no-floppy --fs-uuid --set=root F6AE2C13AE2BCB47 fi chainloader +1 } ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### -------------------------------------------------------------------------------- =============================== sda6/etc/fstab: ================================ -------------------------------------------------------------------------------- # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sda6 during installation UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda7 during installation UUID=52f3dd94-6be7-4a7b-a3ae-f43eb8810483 none swap sw 0 0 -------------------------------------------------------------------------------- =================== sda6: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) 162.831275940 = 174.838751232 boot/grub/grub.cfg 1 163.036647797 = 175.059267584 boot/initrd.img-3.5.0-17-generic 1 206.871749878 = 222.126850048 boot/vmlinuz-3.5.0-17-generic 1 163.036647797 = 175.059267584 initrd.img 1 163.036647797 = 175.059267584 initrd.img.old 1 206.871749878 = 222.126850048 vmlinuz 1 =============================== StdErr Messages: =============================== cat: write error: Broken pipe cat: write error: Broken pipe ADDITIONAL INFORMATION : =================== log of boot-repair 2012-12-11__00h59 =================== boot-repair version : 3.195~ppa28~quantal boot-sav version : 3.195~ppa28~quantal glade2script version : 3.2.2~ppa45~quantal boot-sav-extra version : 3.195~ppa28~quantal boot-repair is executed in installed-session (Ubuntu 12.10, quantal, Ubuntu, x86_64) CPU op-mode(s): 32-bit, 64-bit BOOT_IMAGE=/boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash vt.handoff=7 =================== os-prober: /dev/sda6:The OS now in use - Ubuntu 12.10 CurrentSession:linux /dev/sda1:Windows 7 (loader):Windows:chain =================== blkid: /dev/sda1: UUID="F6AE2C13AE2BCB47" TYPE="ntfs" /dev/sda2: UUID="DC2273012272DFC6" TYPE="ntfs" /dev/sda3: LABEL="New Volume" UUID="1E76E43376E40D79" TYPE="ntfs" /dev/sda5: UUID="5ED60ACDD60AA57D" TYPE="ntfs" /dev/sda6: UUID="9e70fd16-b48b-4f88-adcf-e443aef83124" TYPE="ext4" /dev/sda7: UUID="52f3dd94-6be7-4a7b-a3ae-f43eb8810483" TYPE="swap" 1 disks with OS, 2 OS : 1 Linux, 0 MacOS, 1 Windows, 0 unknown type OS. Warning: extended partition does not start at a cylinder boundary. DOS and Linux will interpret the contents differently. =================== /etc/default/grub : # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: # info -f grub -n 'Simple configuration' GRUB_DEFAULT=0 #GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX="" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" =================== /etc/grub.d/ : drwxr-xr-x 2 root root 4096 Oct 17 20:29 grub.d total 72 -rwxr-xr-x 1 root root 7541 Oct 14 23:06 00_header -rwxr-xr-x 1 root root 5488 Oct 4 15:00 05_debian_theme -rwxr-xr-x 1 root root 10891 Oct 14 23:06 10_linux -rwxr-xr-x 1 root root 10258 Oct 14 23:06 20_linux_xen -rwxr-xr-x 1 root root 1688 Oct 11 19:40 20_memtest86+ -rwxr-xr-x 1 root root 10976 Oct 14 23:06 30_os-prober -rwxr-xr-x 1 root root 1426 Oct 14 23:06 30_uefi-firmware -rwxr-xr-x 1 root root 214 Oct 14 23:06 40_custom -rwxr-xr-x 1 root root 216 Oct 14 23:06 41_custom -rw-r--r-- 1 root root 483 Oct 14 23:06 README =================== UEFI/Legacy mode: This installed-session is not in EFI-mode. EFI in dmesg. Please report this message to [email protected] [ 0.000000] ACPI: UEFI 00000000bafe7000 0003E (v01 DELL QA09 00000002 PTL 00000002) [ 0.000000] ACPI: UEFI 00000000bafe6000 00042 (v01 PTL COMBUF 00000001 PTL 00000001) [ 0.000000] ACPI: UEFI 00000000bafe3000 00256 (v01 DELL QA09 00000002 PTL 00000002) SecureBoot disabled. =================== PARTITIONS & DISKS: sda6 : sda, not-sepboot, grubenv-ok grub2, grub-pc , update-grub, 64, with-boot, is-os, not--efi--part, fstab-without-boot, fstab-without-efi, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, apt-get, grub-install, with--usr, fstab-without-usr, not-sep-usr, standard, farbios, . sda1 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, is-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, haswinload, no-recov-nor-hid, bootmgr, is-winboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, not-far, /mnt/boot-sav/sda1. sda2 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda2. sda3 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda3. sda5 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda5. sda : not-GPT, BIOSboot-not-needed, has-no-EFIpart, not-usb, has-os, 2048 sectors * 512 bytes =================== parted -l: Model: ATA WDC WD7500BPKT-7 (scsi) Disk /dev/sda: 750GB Sector size (logical/physical): 512B/4096B Partition Table: msdos Number Start End Size Type File system Flags 1 106MB 75.2GB 75.1GB primary ntfs boot 2 75.3GB 150GB 75.1GB primary ntfs 3 150GB 170GB 20.1GB primary ntfs 4 170GB 750GB 580GB extended lba 6 170GB 232GB 61.6GB logical ext4 7 232GB 236GB 4181MB logical linux-swap(v1) 5 236GB 750GB 514GB logical ntfs =================== parted -lm: BYT; /dev/sda:750GB:scsi:512:4096:msdos:ATA WDC WD7500BPKT-7; 1:106MB:75.2GB:75.1GB:ntfs::boot; 2:75.3GB:150GB:75.1GB:ntfs::; 3:150GB:170GB:20.1GB:ntfs::; 4:170GB:750GB:580GB:::lba; 6:170GB:232GB:61.6GB:ext4::; 7:232GB:236GB:4181MB:linux-swap(v1)::; 5:236GB:750GB:514GB:ntfs::; =================== mount: /dev/sda6 on / type ext4 (rw,errors=remount-ro) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755) gvfsd-fuse on /run/user/dev/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=dev) /dev/sda1 on /mnt/boot-sav/sda1 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda2 on /mnt/boot-sav/sda2 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda3 on /mnt/boot-sav/sda3 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda5 on /mnt/boot-sav/sda5 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) =================== ls: /sys/block/sda (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro sda1 sda2 sda3 sda4 sda5 sda6 sda7 size slaves stat subsystem trace uevent /sys/block/sr0 (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro size slaves stat subsystem trace uevent /dev (filtered): alarm ashmem autofs binder block bsg btrfs-control bus cdrom cdrw char console core cpu cpu_dma_latency disk dri dvd dvdrw ecryptfs fb0 fb1 fd full fuse hpet input kmsg kvm log mapper mcelog mei mem net network_latency network_throughput null oldmem port ppp psaux ptmx pts random rfkill rtc rtc0 sda sda1 sda2 sda3 sda4 sda5 sda6 sda7 sg0 sg1 shm snapshot snd sr0 stderr stdin stdout uinput urandom v4l vga_arbiter vhost-net video0 zero ls /dev/mapper: control =================== df -Th: Filesystem Type Size Used Avail Use% Mounted on /dev/sda6 ext4 57G 2.7G 51G 6% / udev devtmpfs 1.9G 12K 1.9G 1% /dev tmpfs tmpfs 770M 892K 769M 1% /run none tmpfs 5.0M 0 5.0M 0% /run/lock none tmpfs 1.9G 260K 1.9G 1% /run/shm none tmpfs 100M 44K 100M 1% /run/user /dev/sda1 fuseblk 70G 36G 35G 51% /mnt/boot-sav/sda1 /dev/sda2 fuseblk 70G 66G 4.8G 94% /mnt/boot-sav/sda2 /dev/sda3 fuseblk 19G 87M 19G 1% /mnt/boot-sav/sda3 /dev/sda5 fuseblk 479G 436G 44G 92% /mnt/boot-sav/sda5 =================== fdisk -l: Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x1dc69d0b Device Boot Start End Blocks Id System /dev/sda1 * 206848 146802687 73297920 7 HPFS/NTFS/exFAT /dev/sda2 147007488 293623807 73308160 7 HPFS/NTFS/exFAT /dev/sda3 293623808 332820613 19598403 7 HPFS/NTFS/exFAT /dev/sda4 332822526 1465145343 566161409 f W95 Ext'd (LBA) Partition 4 does not start on physical sector boundary. /dev/sda5 461342720 1465145343 501901312 7 HPFS/NTFS/exFAT /dev/sda6 332822528 453171199 60174336 83 Linux /dev/sda7 453173248 461338623 4082688 82 Linux swap / Solaris Partition table entries are not in disk order =================== Recommended repair Recommended-Repair This setting will reinstall the grub2 of sda6 into the MBR of sda. Additional repair will be performed: unhide-bootmenu-10s grub-install (GRUB) 2.00-7ubuntu11,grub-install (GRUB) 2. Reinstall the GRUB of sda6 into the MBR of sda Installation finished. No error reported. grub-install /dev/sda: exit code of grub-install /dev/sda:0 update-grub Generating grub.cfg ... Found linux image: /boot/vmlinuz-3.5.0-17-generic Found initrd image: /boot/initrd.img-3.5.0-17-generic Found memtest86+ image: /boot/memtest86+.bin Found Windows 7 (loader) on /dev/sda1 Unhide GRUB boot menu in sda6/boot/grub/grub.cfg Boot successfully repaired. You can now reboot your computer. The boot files of [The OS now in use - Ubuntu 12.10] are far from the start of the disk. Your BIOS may not detect them. You may want to retry after creating a /boot partition (EXT4, >200MB, start of the disk). This can be performed via tools such as gParted. Then select this partition via the [Separate /boot partition:] option of [Boot Repair]. (https://help.ubuntu.com/community/BootPartition)

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• C#/.NET Little Wonders: The ConcurrentDictionary

  - by James Michael Hare

  Once again we consider some of the lesser known classes and keywords of C#.  In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns.  Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!).  Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections.  A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace.  These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access.  They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist.  As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection.  Obviously, both are designed for quick – O(1) – lookups of data based on a key.  If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively.  While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking.  Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference.  In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates.  This is where the ConcurrentDictionary really shines!  It achieves its thread-safety with no common lock to improve efficiency.  It actually uses a series of locks to provide concurrent updates, and has lockless reads!  This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences.  Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd().  It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be.  If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does.  This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it.  This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation.  GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary.  The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation.  Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated.  This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly.  The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update.  Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3:  4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4:  5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6).  However, because the reads are dirty, we will quite possibly get a combination of some updated, some original.  My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered.  Also note that both E and F show the value 6.  This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises.  Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature.  You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false.  Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update.  If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true.  If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does.  For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10:  11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate.  If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary.  The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value.  This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11:  12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic.  It is important to note that the methods that use delegates execute those delegates outside of the lock.  This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design.  The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned!  Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate.  Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary.  Now A is done and goes to get the lock, and now sees that the item now exists.  In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int.  And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc).  So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4:  5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8:  9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9:  10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12:  13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26.  But running this in parallel you will get something a bit more complex.  My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3?  This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3.  However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded.  This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time.  As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection.  It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

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• python unhashable type - posting xml data

  - by eterry28

  First, I'm not a python programmer. I'm an old C dog that's learned new Java and PHP tricks, but python looks like a pretty cool language. I'm getting an error that I can't quite follow. The error follows the code below. import httplib, urllib url = "pdb-services-beta.nipr.com" xml = '<?xml version="1.0"?><!DOCTYPE SCB_Request SYSTEM "http://www.nipr.com/html/SCB_XML_Request.dtd"><SCB_Request Request_Type="Create_Report"><SCB_Login_Data CustomerID="someuser" Passwd="somepass" /><SCB_Create_Report_Request Title=""><Producer_List><NIPR_Num_List_XML><NIPR_Num NIPR_Num="8980608" /><NIPR_Num NIPR_Num="7597855" /><NIPR_Num NIPR_Num="10166016" /></NIPR_Num_List_XML></Producer_List></SCB_Create_Report_Request></SCB_Request>' params = {} params['xmldata'] = xml headers = {} headers['Content-type'] = 'text/xml' headers['Accept'] = '*/*' headers['Content-Length'] = "%d" % len(xml) connection = httplib.HTTPSConnection(url) connection.set_debuglevel(1) connection.request("POST", "/pdb-xml-reports/scb_xmlclient.cgi", params, headers) response = connection.getresponse() print response.status, response.reason data = response.read() print data connection.close Here's the error: Traceback (most recent call last): File "C:\Python27\tutorial.py", line 14, in connection.request("POST", "/pdb-xml-reports/scb_xmlclient.cgi", params, headers) File "C:\Python27\lib\httplib.py", line 958, in request self._send_request(method, url, body, headers) File "C:\Python27\lib\httplib.py", line 992, in _send_request self.endheaders(body) File "C:\Python27\lib\httplib.py", line 954, in endheaders self._send_output(message_body) File "C:\Python27\lib\httplib.py", line 818, in _send_output self.send(message_body) File "C:\Python27\lib\httplib.py", line 790, in send self.sock.sendall(data) File "C:\Python27\lib\ssl.py", line 229, in sendall v = self.send(data[count:]) TypeError: unhashable type My log file says that the xmldata parameter is empty. Any ideas?

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• Serialization of Queue type- Serialization not working; C#

  - by Soham

  Hi All, Consider this piece of code: private Queue Date=new Queue(); //other declarations public DateTime _Date { get { return (DateTime)Date.Peek();} set { Date.Enqueue(value); } } //other properties and stuff.... public void UpdatePosition(...) { //other code IFormatter formatter = new BinaryFormatter(); Stream Datestream = new MemoryStream(); formatter.Serialize(Datestream, Date); byte[] Datebin = new byte[2048]; Datestream.Read(Datebin,0,2048); //Debug-Bug Console.WriteLine(Convert.ToString(this._Date)); Console.WriteLine(BitConverter.ToString(Datebin, 0, 3)); //other code } The output of the first writeline is perfect. I.e to check if really the Queue is initialised or not. It is. The right variables are stored and et. all [I inserted a value in that Q, that part of the code is not shown] But the second writeline is not giving the right expected answer: It serializes the entire Queue to 00-00-00. Want some serious help! Soham

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• fortran 90 user defined type, passing by value ?

  - by user279137

  I have an issue in fortran 90. I have a user defined type and when I call one of the MPI subroutines the data looks to be passed by values (not address, as I thought it should). The output arguments aren't modified. It seems to be specific to the MPI calls I tried the same thing in a simple test, and I can change the passed in values in the calling scope. I'm not sure why this is because I thought fortran always pass by address. Any idea what could be going on? Just to be clear the commented snippet shows how the calls are made. The in the first call, c%NSubDomains, is an output argument and should be modified in the calling scope, but its not. WHen I call with an array rather than a member of user defined type it works, in the uncommented snippet. ! ! This doesn't work output values aren't modified ?? ! call MPI_Dims_create(c%NProcs,c%NDims,c%NSubDomains,iErr) nsubs(:)=0 call MPI_Dims_create(c%NProcs,c%NDims,nsubs,iErr) c%NSubDomains=nsubs Thanks

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• sqlalchemy date type in 0.6 migration using mssql

  - by nosklo

  I'm connection to mssql server through pyodbc, via FreeTDS odbc driver, on linux ubuntu 10.04. Sqlalchemy 0.5 uses DATETIME for sqlalchemy.Date() fields. Now Sqlalchemy 0.6 uses DATE, but sql server 2000 doesn't have a DATE type. How can I make DATETIME be the default for sqlalchemy.Date() on sqlalchemy 0.6 mssql+pyodbc dialect? I'd like to keep it as clean as possible. Here's code to reproduce the issue: import sqlalchemy from sqlalchemy import Table, Column, MetaData, Date, Integer, create_engine engine = create_engine( 'mssql+pyodbc://sa:sa@myserver/mydb?driver=FreeTDS') m = MetaData(bind=engine) tb = sqlalchemy.Table('test_date', m, Column('id', Integer, primary_key=True), Column('dt', Date()) ) tb.create() And here is the traceback I'm getting: Traceback (most recent call last): File "/tmp/teste.py", line 15, in <module> tb.create() File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/schema.py", line 428, in create bind.create(self, checkfirst=checkfirst) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1647, in create connection=connection, **kwargs) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1682, in _run_visitor **kwargs).traverse_single(element) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/sql/visitors.py", line 77, in traverse_single return meth(obj, **kw) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/ddl.py", line 58, in visit_table self.connection.execute(schema.CreateTable(table)) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1157, in execute params) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1210, in _execute_ddl return self.__execute_context(context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1268, in __execute_context context.parameters[0], context=context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1367, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1360, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/default.py", line 277, in do_execute cursor.execute(statement, parameters) sqlalchemy.exc.ProgrammingError: (ProgrammingError) ('42000', '[42000] [FreeTDS][SQL Server]Column or parameter #2: Cannot find data type DATE. (2715) (SQLExecDirectW)') '\nCREATE TABLE test_date (\n\tid INTEGER NOT NULL IDENTITY(1,1), \n\tdt DATE NULL, \n\tPRIMARY KEY (id)\n)\n\n' ()

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• docs/examples on libxml2 type system?

  - by Wang

  I'm reading through the libxml2 API and examples on xmlsoft.com and having some real difficulty wrapping my head around the type system. For example, the _xmlAttribute struct has an xmlChar* field called name. This obviously refers to the name of the attribute (e.g., "bar" for the struct tied to the element <foo bar='baz' />). The _xmlAttribute struct also has a field called value, which I would expect to be "baz", except the type is xmlNodePtr. Um, what? I guess I could write up some test code and examine the memory in gdb, but there has to be an easier way. Has anyone written up examples of the data structures generated by a libxml2 parser? I'm looking for an English prose text, not generated documentation, that will walk me through the various types and the values they take when parsing some example bit of XML. Bonus points if it presents only the subset of libxml2 needed to read and write a config file---no namespaces or XPath or even modifying an existing document, just parse some XML, access the data, and then write it out again.

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• MATLAB Builder NE (.NET Assembly) Data type question

  - by Brett

  Hi coders, I am using MATLAB Builder NE (MATLAB's integrated .NET assmebly builder), but I am having an issue with data types. I have compiled a small, very simple, function in matlab and build it for .NET. I am able to call the namespace and even the function just fine. However, my function returns a value, and MATLAB defaults to returning it as an "object[]" data type. However, I know that the value is an integer, but I can't figure out how to cast it. My MATLAB function looks like this: function addValue = Myfunction(value1, value2) addValue=value1+value2; end Pretty simple right? And then in .NET I can call it as: xClass.addValue (1, 3, 4); where xClass is the name of the MATLAB built class but when I try: int x = xClass.addValue (1, 3, 4); C# errors out. Typical .NET casting (int) doesn't work. The compiler states it cannot convert object[] to int. Does anyone have experience with the .NET builder in MATLAB that can help me with this? It is really throwing me for a loop. I have scanned through most of the MATLAB BUILDER doc (484 pages!) with zero help. Thank you, Brett

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• Calling a method with an arg of Class<T> where T is a parameterized type

  - by Brian Ferris

  I'm attempting to call a constructor method that looks like: public static SomeWrapper<T> method(Class<T> arg); When T is an unparameterized type like String or Integer, calling is straightforward: SomeWrapper<String> wrapper = method(String.class); Things get tricky when T is a parameterized type like List<String>. The following is not valid: SomeWrapper<List<String>> wrapper = method(List<String>.class); About the only thing I could come up with is: List<String> o = new ArrayList<String>(); Class<List<String>> c = (Class<List<String>>) o.getClass(); SomeWrapper<List<String>> wrapper = method(c); Surely there is an easier way that doesn't require the construction of an additional object?

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