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• System.Dynamic bug?

  - by ControlFlow

  While I playing with the C# 4.0 dynamic, I found strange things happening with the code like this: using System.Dynamic; sealed class Foo : DynamicObject { public override bool TryInvoke( InvokeBinder binder, object[] args, out object result) { result = new object(); return true; } static void Main() { dynamic foo = new Foo(); var t1 = foo(0); var t2 = foo(0); var t3 = foo(0); var t4 = foo(0); var t5 = foo(0); } } Ok, it works but... take a look at IntelliTrace window: So every invokation (and other operations too on dynamic object) causes throwing and catching strange exceptions twice! I understand, that sometimes exceptions mechanism may be used for optimizations, for example first call to dynamic may be performed to some stub delegate, that simply throws exception - this may be like a signal to dynamic binder to resolve an correct member and re-point delegate. Next call to the same delegate will be performed without any checks. But... behavior of the code above looks very strange. Maybe throwing and catching exceptions twice per any operation on DynamicObject - is a bug?

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• Converting LINQ to Twitter to Twitter API v1.1

  - by Joe Mayo

  Twitter recently updated their API to v1.1 (Current status: API v1.1). Naturally, LINQ to Twitter  needed to be updated too. This blog post outlines the changes made to LINQ to Twitter during this conversion and highlights important features that LINQ to Twitter developers will want to know. Overall Impact Generally speaking, Twitter API v1.1 is semantically very much the same as it’s predecessor. The base URL changed and so did a few resource segments, but the resources themselves are still intact. The good news is that LINQ to Twitter has always shielded the developer from this plumbing, so the entities, types, and filters didn’t change much at all.  The following sections describe what did  change. Authentication In Twitter API v1.0 authentication was not required for some resources, such as user timelines and search. However, that’s all changed because *all* queries must be authenticated in Twitter API v1.1. LINQ to Twitter has various types of authorizers you can use, supporting whatever OAuth options are available via Twitter.  You can see the LINQ to Twitter documentation, Securing Your Applications, for more info on OAuth support. The New Search One of the larger changes to the API was Search. To be more specific, the Search entity now contains a List<Status>, named Statuses, to hold results.  Additionally, any meta-data associated with the search is now in a property named SearchMetaData. The change to the Search entity and responses is the big change, but the good news is that your Search query syntax doesn’t change. Different Rate Limits The issue of rate limits itself is contentious, but this discussion is focused on the coding experience and I’ll leave the politics to those who prefer to engage in that activity. What’s important here is that both headers and resources have changed. You should review Twitter’s Rate Limit documentation to understand what the changes mean.  A quick explanation is that rate limits are applied individually to each resource in 15 minute time intervals. In LINQ to Twitter these changes surface on the Help entity, via HelpType.RateLimits. The RateLimits query has a Resources filter where you can specify a comma-separated list of categories to return rate limit info for.  The results materialize in the RateLimits dictionary, keyed on category. The Help entity also has a RateLimitsAuthorizationContext, holding the Access Token for the user performing queries – and to whom the rate limits apply. In addition to the new RateLimits query, there are new RateLimit headers that appear in the query response, whose HTTP header name is of the form X-Rate-Limit… which is different from the previous header name. LINQ to Twitter surfaces these headers via the existing properties of the TwitterContext instance. For anyone who retrieved rate limit information via the Headers property of TwitterContext, you should be aware of the new header names.  I haven’t done anything with Feature rate limit properties yet, but they appear to no longer be available – this will require more follow-up. Error Handling Twitter API v1.1 has a new format for Error Codes & Responses. LINQ to Twitter wraps these messages in the TwitterQueryException, which has been updated appropriately. The Message property of TwitterQueryException now reflects the Twitter error message, when available. There’s also a new ErrorCode that’s populated with the message error code. Parameters Most parameters stayed the same, but one of interest is Include Entities (different from LINQ to Twitter data object entities). Entities are metadata hanging off tweets, that provide start/end position in the tweet and other information for mentions, urls, hash tags, and media. Entities used to not be included unless you specified you wanted them. Now, in v1.1, entities are included by default for all APIs that return a Status.  If you were always setting IncludeEntities to true, then you won’t see a change. However, be aware that you’ll now be receiving additional data in your response from Twitter, which will explain a sudden increase in bandwidth utilization. This might or might not  matter to you  depending on the requirements of your application, but you should be aware of it. Everything Else There might be small changes here and there that I haven’t mentioned, but these were the ones you should be most aware of.  Streams didn’t change, but Twitter will be deprecating username/password authentication on public streams, in favor of OAuth, so you’ll be seeing me make that change some time in the future.  Also, Twitter will continue to evolve the API and you can expect that LINQ to Twitter will change accordingly. Summary The big changes to Twitter API were Authentication, Search, Rate Limits, and Error Handling. All API calls must be authenticated. You’ll need to change your code to read Search results differently, but the query is much the same as you use now. There’s a new RateLimits API, one of the Help queries.  Also, the new error messages are integrated into TwitterQueryException. Besides these changes, I expect  most others to be small or affect a smaller percentage of developers.  You can get the latest version of LINQ to Twitter from NuGet or visit the LINQ to Twitter download page at CodePlex.com.   @JoeMayo

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• T-SQL Dynamic SQL and Temp Tables

  - by George

  It looks like #temptables created using dynamic SQL via the EXECUTE string method have a different scope and can't be referenced by "fixed" SQLs in the same stored procedure. However, I can reference a temp table created by a dynamic SQL statement in a subsequence dynamic SQL but it seems that a stored procedure does not return a query result to a calling client unless the SQL is fixed. A simple 2 table scenario: I have 2 tables. Let's call them Orders and Items. Order has a Primary key of OrderId and Items has a Primary Key of ItemId. Items.OrderId is the foreign key to identify the parent Order. An Order can have 1 to n Items. I want to be able to provide a very flexible "query builder" type interface to the user to allow the user to select what Items he want to see. The filter criteria can be based on fields from the Items table and/or from the parent Order table. If an Item meets the filter condition including and condition on the parent Order if one exists, the Item should be return in the query as well as the parent Order. Usually, I suppose, most people would construct a join between the Item table and the parent Order tables. I would like to perform 2 separate queries instead. One to return all of the qualifying Items and the other to return all of the distinct parent Orders. The reason is two fold and you may or may not agree. The first reason is that I need to query all of the columns in the parent Order table and if I did a single query to join the Orders table to the Items table, I would be repoeating the Order information multiple times. Since there are typically a large number of items per Order, I'd like to avoid this because it would result in much more data being transfered to a fat client. Instead, as mentioned, I would like to return the two tables individually in a dataset and use the two tables within to populate a custom Order and child Items client objects. (I don't know enough about LINQ or Entity Framework yet. I build my objects by hand). The second reason I would like to return two tables instead of one is because I already have another procedure that returns all of the Items for a given OrderId along with the parent Order and I would like to use the same 2-table approach so that I could reuse the client code to populate my custom Order and Client objects from the 2 datatables returned. What I was hoping to do was this: Construct a dynamic SQL string on the Client which joins the orders table to the Items table and filters appropriate on each table as specified by the custom filter created on the Winform fat-client app. The SQL build on the client would have looked something like this: TempSQL = " INSERT INTO #ItemsToQuery OrderId, ItemsId FROM Orders, Items WHERE Orders.OrderID = Items.OrderId AND /* Some unpredictable Order filters go here */ AND /* Some unpredictable Items filters go here */ " Then, I would call a stored procedure, CREATE PROCEDURE GetItemsAndOrders(@tempSql as text) Execute (@tempSQL) --to create the #ItemsToQuery table SELECT * FROM Items WHERE Items.ItemId IN (SELECT ItemId FROM #ItemsToQuery) SELECT * FROM Orders WHERE Orders.OrderId IN (SELECT DISTINCT OrderId FROM #ItemsToQuery) The problem with this approach is that #ItemsToQuery table, since it was created by dynamic SQL, is inaccessible from the following 2 static SQLs and if I change the static SQLs to dynamic, no results are passed back to the fat client. 3 around come to mind but I'm look for a better one: 1) The first SQL could be performed by executing the dynamically constructed SQL from the client. The results could then be passed as a table to a modified version of the above stored procedure. I am familiar with passing table data as XML. If I did this, the stored proc could then insert the data into a temporary table using a static SQL that, because it was created by dynamic SQL, could then be queried without issue. (I could also investigate into passing the new Table type param instead of XML.) However, I would like to avoid passing up potentially large lists to a stored procedure. 2) I could perform all the queries from the client. The first would be something like this: SELECT Items.* FROM Orders, Items WHERE Order.OrderId = Items.OrderId AND (dynamic filter) SELECT Orders.* FROM Orders, Items WHERE Order.OrderId = Items.OrderId AND (dynamic filter) This still provides me with the ability to reuse my client sided object-population code because the Orders and Items continue to be returned in two different tables. I have a feeling to, that I might have some options using a Table data type within my stored proc, but that is also new to me and I would appreciate a little bit of spoon feeding on that one. If you even scanned this far in what I wrote, I am surprised, but if so, I woul dappreciate any of your thoughts on how to accomplish this best.

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• Nginx dynamic upstream configuration / routing

  - by Dan Sosedoff

  I was experimenting with dynamic upstream configuration for nginx and cant find any good solution to implement upstream configuration from third-party source like redis or mysql. The idea behind it is to have a single file configuration in primary server and proxy requests to various app servers based on environment conditions. Think of dynamic deployments where you have X servers that are running Y workers on different ports. For instance, i create a new app and deploy. App manager selects a server and then rolls out a worker (Ruby/PHP/Python) and then reports the ip:port to the central database with status "up". At this time when i go to the given url nginx should proxy all requests to the specified ip:port upstream. The whole thing is pretty similar to what heroku does, except this proof-of-concept is not supposed to be production ready, mostly for internal needs. The easiest solution i found was using resolver with ruby-based DNS server. It works, nginx gets the IP address correctly, but the only problem is that you cant define port number for that IP. Second solution (which i havent tried yet) is to roll something else as a proxy server, maybe written in Erlang. In this case we need to use something to serve static content. Any ideas how to implement this in more flexible and stable way? P.S. Some research options: http://openresty.org/#DynamicRoutingBasedOnRedis https://github.com/nodejitsu/node-http-proxy

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• Canonical Redirect on Dynamic Mass Virtual Hosts on Apache

  - by Josh

  I have a Web app on Apache that allows users to point their domain to the server. Right now I'm using Apache's dynamic mass virtual hosts with an entry VirtualDocumentRoot /www/hosts/%0/docs So with www.companydomain.com it points to /www/hosts/www.companydomain.com/docs The problem is when the user goes to companydomain.com it will point to /www/hosts/companydomain.com/docs Is there an easy way to automatically have Apache check to see if a directory exists for the virtual host, and if not, look for the host name with "www." in front of it? Other subdomains are fine (i.e. abc.domain.com should point to a diff. directory than def.domain.com) but the whole "www" issue is a mystery to me. I am using dynamic mass virtual hosts so the server does not have to restart after each registration for the application. If there is a different way that is fine as long as apache isn't restarted each time. How can I accomplish this? Worst case scenario if there were a way to redirect to a "default" location on the server if not found I could always do a check via PHP or something but I feel like that is a bit hacked together and there has to be a more efficient way. Thanks in advance!

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• Database and logic layer for ASP.NET MVC application

  - by Ismail

  I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern as it allows to apply filter in logic layer rather than in data access layer. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right? So questions basically are - Is MySQL to Linq possible? If yes where can I get more details on it? Pros and cons of using EntityFramework with MySQL? Will it be easy to access data using EntityFramework with MySQL? Will I be able to implement repository patter which allows applying filter in logic layer rather than data access layer (when I use EntityFramework with MySQL) Does it fetches hell lot of data from database and then apply filter on it? If it sounds too many questions from my side in that case, if you can just let me know what you will do (with a considerable reason) in this situation as an experienced person in this area, that should answer my question.

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• ASP.NET MVC 2: Updating a Linq-To-Sql Entity with an EntitySet

  - by Simon

  I have a Linq to Sql Entity which has an EntitySet. In my View I display the Entity with it's properties plus an editable list for the child entites. The user can dynamically add and delete those child entities. The DefaultModelBinder works fine so far, it correctly binds the child entites. Now my problem is that I just can't get Linq To Sql to delete the deleted child entities, it will happily add new ones but not delete the deleted ones. I have enabled cascade deleting in the foreign key relationship, and the Linq To Sql designer added the "DeleteOnNull=true" attribute to the foreign key relationships. If I manually delete a child entity like this: myObject.Childs.Remove(child); context.SubmitChanges(); This will delete the child record from the DB. But I can't get it to work for a model binded object. I tried the following: // this does nothing public ActionResult Update(int id, MyObject obj) // obj now has 4 child entities { var obj2 = _repository.GetObj(id); // obj2 has 6 child entities if(TryUpdateModel(obj2)) //it sucessfully updates obj2 and its childs { _repository.SubmitChanges(); // nothing happens, records stay in DB } else ..... return RedirectToAction("List"); } and this throws an InvalidOperationException, I have a german OS so I'm not exactly sure what the error message is in english, but it says something along the lines of that the entity needs a Version (Timestamp row?) or no update check policies. I have set UpdateCheck="Never" to every column except the primary key column. public ActionResult Update(MyObject obj) { _repository.MyObjectTable.Attach(obj, true); _repository.SubmitChanges(); // never gets here, exception at attach } I've read alot about similar "problems" with Linq To Sql, but it seems most of those "problems" are actually by design. So am I right in my assumption that this doesn't work like I expect it to work? Do I really have to manually iterate through the child entities and delete, update and insert them manually? For such a simple object this may work, but I plan to create more complex objects with nested EntitySets and so on. This is just a test to see what works and what not. So far I'm disappointed with Linq To Sql (maybe I just don't get it). Would be the Entity Framework or NHibernate a better choice for this scenario? Or would I run into the same problem?

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• Proper way to use Linq with WPF

  - by Ingó Vals

  I'm looking for a good guide into the right method of using Linq to Sql together with WPF. Most guides only go into the bare basics like how to show data from a database but noone I found goes into how to save back to the database. Can you answer or point out to me a guide that can answer these questions. I have a separate Data project because the same data will also be used in a web page so I have the repository method. That means I have a seperate class that uses the DataContext and there are methods like GetAllCompanies() and GetCompanyById ( int id ). 1) Where there are collections is it best to return as a IQueryable or should I return a list? Inside the WPF project I have seen reccomendations to wrap the collection in a ObservabgleCollection. 2) Why should I use ObservableCollection and should I use it even with Linq / IQueryable Some properties of the linq entities should be editable in the app so I set them to two-way mode. That would change the object in the observableCollection. 3) Is the object in the ObservableCollection still a instance of the original linq entity and so is the change reflected in the database ( when submitchanges is called ) I should have somekind of save method in the repository. But when should I call it? What happens if someone edits a field but decides not to save it, goes to another object and edits it and then press save. Doesn't the original change also save? When does it not remember the changes to a linq entity object anymore. Should I instance the Datacontext class in each method so it loses scope when done. 4) When and how to call the SubmitChanges method 5) Should I have the DataContext as a member variable of the repository class or a method variable To add a new row I should create a new object in a event ( "new" button push ) and then add it to the database using a repo method. 6) When I add the object to the database there will be no new object in the ObservableCollection. Do I refresh somehow. 7) I wan't to reuse the edit window when creating new but not sure how to dynamically changing from referencing selected item from a listview to this new object. Any examples you can point out.

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• Are elements returned by Linq-to-Entities query streamed from the DB one at the time or are they retrieved all at once?

  - by carewithl

  Are elements returned by Linq-to-Entities query streamed from the database one at the time ( as they are requested ) or are they retrieved all at once: SampleContext context = new SampleContext(); // SampleContext derives from ObjectContext var search = context.Contacts; foreach (var contact in search) { Console.WriteLine(contact.ContactID); // is each Contact retrieved from the DB // only when foreach requests it? } thank you in advance

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• Can I have both Windows dynamic disk partition and some other non-Windows partition on the same disk?

  - by haimg

  When a basic Windows disk is converted to dynamic, Windows creates a partition that span the whole disk with the type of "Windows LVM" and manages its dynamic partitions within this space. So even if there is still free space on this disk, it is not visible to any other OS besides Windows. This happens with MBR and GPT disks both. I would like to share a Windows dynamic disk with some other OS. I have to have dynamic disks because I use Windows SoftRaid (mirrors). So, my questions are: Is there any way to "force" Windows to take up less then the whole disk when it converts a basic disk to dynamic? Will Windows tolerate having some other non-Windows partition on its dynamic disk?

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• LinqToSQL _conn ? LinqToSQLConnection ?

  - by nCdy

  here is a code : using System; using Nemerle.Collections; using Nemerle.Text; //using Nemerle.Utility; using System.Linq; using Nemerle.Data.Linq; using NUnit.Framework; using System.Data.Linq; namespace LinqTestes { [TestFixture] public class Linq2SqlTests { static ReadConnectionString() : string { def currAssm = Uri(typeof(Linq2SqlTests).Assembly.CodeBase).LocalPath; def path = IO.Path.GetDirectoryName(currAssm); def connStrPath = IO.Path.Combine(path, "connectionString.txt"); def connStr = try { IO.File.ReadAllText(connStrPath, Text.Encoding.UTF8) } catch { | e is IO.FileNotFoundException => throw IO.FileNotFoundException( $"You should define connection string to NorthWind DB in: '$connStrPath'", e.FileName, e) }; connStr } _conn : LinqDataConnection = LinqDataConnection(ReadConnectionString()); and I'm making the same but what is LinqDataConnection type ? and where does it comes from ?

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• Dynamic DNS with Comcast

  - by colithium

  I've just recently moved across town. Previously, I had Dynamic DNS set up so I could remotely connect to my desktop (primarily to use TightVNC). My ISP was Comcast and I'm in the Denver, Colorado area. Currently, I'm still with Comcast and still in Denver. My router connects to the internet just fine and my Dynamic DNS record over at DynDNS did get updated with my router's current external IP address. So my router, DynDNS, and public DNS records all agree what my IP address is. However, I can't actually connect to anything from the outside world. My trace route to Google looks something like: Tracing route to google.com [74.125.19.147] 1 3 ms 1 ms 1 ms 192.168.1.1 (this is the internal IP address of my router) 2 * * * Request timed out. 3 9 ms 8 ms 10 ms te-8-2-ur02.wheatridge.co.denver.comcast.net [68.85.221.177] 4 12 ms 12 ms 19 ms te-0-8-0-2-ar02.aurora.co.denver.comcast.net [68.86.103.97] 5 16 ms 13 ms 11 ms pos-0-3-0-0-cr01.denver.co.ibone.comcast.net [68.86.91.1] 6 28 ms 28 ms 27 ms pos-0-9-0-0-cr01.dallas.tx.ibone.comcast.net [68.86.85.174] 7 29 ms 27 ms 28 ms pos-0-1-0-0-pe01.1950stemmons.tx.ibone.comcast.net [68.86.86.94] 8 66 ms 108 ms * 75.149.231.70 9 65 ms 68 ms 93 ms 72.14.233.77 10 67 ms 66 ms 66 ms 72.14.233.111 11 67 ms 67 ms 69 ms 216.239.43.144 12 68 ms 71 ms 73 ms 209.85.249.30 13 66 ms 66 ms 68 ms nuq04s01-in-f147.1e100.net [74.125.19.147] This is what the trace route looks like from an outside source to my DynDNS domain name: traceroute to 98.245.67.65 (98.245.67.65) 1 illuminati-130 138.67.130.61 2 138.67.63.253 138.67.63.253 3 vermiculite 138.67.253.20 4 csm-ct-gw 138.67.253.244 5 138.67.253.2 138.67.253.2 6 ge-7-24-ar01.denver.co.denver.comcast.net 68.86.128.17 7 te-0-4-0-0-ar02.denver.co.denver.comcast.net 68.86.179.21 8 te-9-3-ur01.wheatridge.co.denver.comcast.net 68.86.103.18 9 * * * {Times Out} Now my guess is, whatever is sitting just beyond my router (what the modem connects to) is gumming things up. Even though the routes aren't EXACTLY the same, that appears to be the spot that the trace route either stops or doesn't get a response. My question is, for Comcast networks (particularly in Denver), what would be the device that typically sits there? Is there anything I can do about it? That device seems to not respond to PING but does forward it along when I'm going outwards. But it looks like it eats it when the request is coming in. It's hard to prove that from these logs but I'm assuming that's the case because my router used to accept connections from the outside and I haven't changed anything on it.

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• Can't activate dynamic disk

  - by SuperFurryToad

  For some reason I can't activate a dynamic disk connected to my PC via a USB hard disk enclosure. It has activated previously without any problems. When I check the event logs, I get this message every time I try to activate the disk: dmio: Harddisk2 write error at block 2930277167: status 0xc0000015

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• Dynamic Disk Start on Boot

  - by Xiuhtecuhtli

  Is there a way to make a Dynamic Disc Automatically Come on line after a reboot. at the moment i must manually Bring the disk "online". I was thinking a Startup Script would do the trick. does anyone know of a URL HOWTO or a Premade script to do this?

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• Using dynamic dns updater as Windows service

  - by Sami-L

  Currently I am using a dynamic dns updater software on Windows, but to keep it updating I have not to close it, also the software is not able to run at backgoud, I searched on google but the answer became complicated since there are many details to pay attention to, free, not free, installed on machine, configured on router, trusted, not trusted ... So please help me find a trusted free dns updater for Windows which can run as service, and maybe which can send email when update fails.

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• Can you recommend a good Dynamic DNS provider?

  - by Peltier

  I want to use dynamic dns for my home server. Can you recommend a provider that works well?

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• Recover data from a Windows Dynamic Volume Spanned Disk

  - by iCe

  I have a dynamic volume created with two spanned partitions over two disk. Recently, one disk has started failing, and I want to copy the data inside that disk to another disk, before replacing it. However I don't know how to select only what is inside the failing disk, because the partitions spans across both disks. Maybe imaging the entire disk should do the work? Or I have to copy all the data from both disks? Thanks in advance!

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• How to Link VS2010 Database Project and LINQ to SQL

  - by Jason

  As I am working with the new database projects in VS2010, and as I am learning LINQ to SQL, I am curious as to the best way to link the two groups of information so that when I update one, the other updates along with it. From my research here at SO, as well as in Google, it appears the general rule of thumb is: "Build the database, and then create your LINQ to SQL classes." Of course, if I make a change in my database, the LINQ to SQL doesn't update automatically and I have to do it by hand. This is fairly simple right now as my database is small, but I am curious if there is an easier way for this to happen. In addition, the LINQ to SQL tool is pretty nice. The ability to create tables, add associations, and even create inheritance is very simple. As my second question, I am curious as to whether or not VS2010 can work the other way - I design the database in the DBLM file and then link it back to my database project. I appreciate any help with either of these two questions. I'm really interested in making this as easy as possible to reduce errors during development and improve the speed at which changes can be made.

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• Selecting a multi-dimensional array in LINQ

  - by mckhendry

  I have a task where I need to translate a DataTable to a two-dimensional array. That's easy enough to do by just looping over the rows and columns (see example below). private static string[,] ToArray(DataTable table) { var array = new string[table.Rows.Count,table.Columns.Count]; for (int i = 0; i < table.Rows.Count; ++i) for (int j = 0; j < table.Columns.Count; ++j) array[i, j] = table.Rows[i][j].ToString(); return array; } What I'd really like to do is use a select statement in LINQ to generate that 2D array. Unfortunately it looks like there is no way in LINQ to select a multidimensional array. Yes, I'm aware that I can use LINQ to select a jagged array, but that's not what I want. Is my assumption correct, or is there a way to use LINQ to select a multi-dimensional array?

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• Merging sequences by type With LINQ

  - by jankor

  I want to use LINQ to convert this IEnumerable<int>[] value1ByType = new IEnumerable<int>[3]; value1ByType[0]= new [] { 0}; value1ByType[1]= new [] {10,11}; value1ByType[2]= new [] {20}; var value2ToType = new Dictionary<int,int> { {100,0}, {101,1}, {102,2}, {103,1}}; to this var value2ToValue1 = new Dictionary<int,int> { {100, 0}, {101,10}, {102,20}, {103,11}}; Is there a way to do this with LINQ? Without LINQ I would use multiple IEnumerators, one for each IEnumerable of value1ByType. like this: // create enumerators var value1TypeEnumerators = new List<IEnumerator<int>>(); for (int i = 0; i < value1ByType.Length; i++) { value1TypeEnumerators.Add(value1ByType[i].GetEnumerator()); value1TypeEnumerators[i].MoveNext(); } // create wanted dictionary var value2ToValue1 = new Dictionary<int, int>(); foreach (var item in Value2ToType) { int value1=value1TypeEnumerators[item.Value].Current; value2ToValue1.Add(item.Key, value1); value1TypeEnumerators[item.Value].MoveNext(); } Any Idea how to do this in LINQ?

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• LINQ Query please help C#.Net.

  - by Paul Matthews

  I'm very new to LINQ and struggling to find the answers. I have a simple SQL query. Select ID, COUNT(ID) as Selections, OptionName, SUM(Units) as Units FROM tbl_Results GROUP BY ID, OptionName. The results I got were: '1' '4' 'Approved' '40' '2' '1' 'Rejected' '19' '3' '2' 'Not Decided' '12' Due to having to encrypt all my data in the database I'm unable to do sums. Therefore I have now brought back the data and decrypt it in the application layer. Results would be: '1' 'Approved' '10' '3' 'Not Deceided' '6' '2' 'Rejected' '19' '1' 'Approved' '15' '1' 'Approved' '5' '3' 'Not Deceided' '6' '1' 'Approved' '10' using a simple class I have called back the above results, and put them in a list class. public class results { public int ID {get;set;} public string OptionName {get;set;} public int Unit {get;set;} } I almost have the LINQ query to bring back the results like the SQL query at the top var q = from r in Results group p.Unit by p.ID int g select new {ID = g.Key, Selections = g.Count(), Units = g.Sum()}; How do I ensure my LINQ query also give me the Option Name? Also if I created a class called Statistics to hold my results how would I modify the LINQ query to give me list result set? public class results { public int ID {get;set;} public int NumberOfSelections { get; set; } public string OptionName {get;set;} public int UnitTotal {get;set;} }

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• Show me your Linq to SQL architectures!

  - by Brad Heller

  I've been using Linq to SQL for a new implementation that I've been working on. I have about 5000 lines of code and am a little ways from a solid demo. I've been pretty satisfied with Linq to SQL so far -- the tools are excellent and pretty painless and it allows you to get a DAL up and running quickly. That said, there are some major draw backs that I just keep hitting over and over again. Namely how to handle separation of concerns between my DAL and my business layer and juggling that with different data contexts. Here is the architecture I've been using: My repositories do all my data access and they return Linq to SQL objects. Each of my Linq to SQL objects implements an IDetachable interface. A typical implementation looks like this: partial class PaymentDetail : IDetachable { #region IDetachable Members public bool IsAttached { get { return PropertyChanging != null; } } public void Detach() { if (IsAttached) { PropertyChanged = null; PropertyChanging = null; Transaction.Detach(); } } #endregion } Every time I do a DAL operation in my repository I "detach" when I'm done with the object (and it should theoretically detach from any child objects) to remove the DataContext's context. Like I said, this works pretty well, but there are some edge cases that seem to be a big pain in the ass. For instance, my Transaction object has many PaymentDetails. Even when there are no PaymentDetails in that collection it's still attached to the DataContext's context! Thus, if I try to update (I update by Attach()ing to the object and then SubmitChanges()) I get that dreaded "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." message. Anyway, I'm starting to doubt that this technology was a good gamble. Has anyone got a decent architecture that they're willing to share? I'd really love to use this technology but I feel like I spend 1/3 of my time just debugging is retarded quirks!

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• VB.NET switching from ADO.NET to LINQ

  - by Cj Anderson

  I'm VERY new to Linq. I have an application I wrote that is in VB.NET 2.0. Works great, but I'd like to switch this application to Linq. I use ADO.NET to load XML into a datatable. The XML file has about 90,000 records in it. I then use the Datatable.Select to perform searches against that Datatable. The search control is a free form textbox. So if the user types in terms it searches instantly. Any further terms that are typed in continue to restrict the results. So you can type in Bob, or type in Bob Barker. Or type in Bob Barker Price is Right. The more criteria typed in the more narrowed your result. I bind the results to a gridview. Moving forward what all do I need to do? From a high level, I assume I need to: 1) Go to Project Properties -- Advanced Compiler Settings and change the Target framework to 3.5 from 2.0. 2) Add the reference to System.XML.Linq, Add the Imports statement to the classes. So I'm not sure what the best approach is going forward after that. I assume I use XDocument.Load, then my search subroutine runs against the XDocument. Do I just do the standard Linq query for this sort of repeated search? Like so: var people = from phonebook in doc.Root.Elements("phonebook") where phonebook.Element("userid") = "whatever" select phonebook; Any tips on how to best implement?

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• Alternatives to LINQ To SQL on high loaded pages

  - by Alex

  To begin with, I LOVE LINQ TO SQL. It's so much easier to use than direct querying. But, there's one great problem: it doesn't work well on high loaded requests. I have some actions in my ASP.NET MVC project, that are called hundreds times every minute. I used to have LINQ to SQL there, but since the amount of requests is gigantic, LINQ TO SQL almost always returned "Row not found or changed" or "X of X updates failed". And it's understandable. For instance, I have to increase some value by one with every request. var stat = DB.Stats.First(); stat.Visits++; // .... DB.SubmitChanges(); But while ASP.NET was working on those //... instructions, the stats.Visits value stored in the table got changed. I found a solution, I created a stored procedure UPDATE Stats SET Visits=Visits+1 It works well. Unfortunately now I'm getting more and more moments like that. And it sucks to create stored procedures for all cases. So my question is, how to solve this problem? Are there any alternatives that can work here? I hear that Stackoverflow works with LINQ to SQL. And it's more loaded than my site.

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• LINQ Joins - Performance

  - by Meiscooldude

  I am curious on how exactly LINQ (not LINQ to SQL) is performing is joins behind the scenes in relation to how Sql Server performs joins. Sql Server before executing a query, generates an Execution Plan. The Execution Plan is basically an Expression Tree on what it believes is the best way to execute the query. Each node provides information on whether to do a Sort, Scan, Select, Join, ect. On a 'Join' node in our execution plan, we can see three possible algorithms; Hash Join, Merge Join, and Nested Loops Join. Sql Server will choose which algorithm to for each Join operation based on expected number of rows in Inner and Outer tables, what type of join we are doing (some algorithms don't support all types of joins), whether we need data ordered, and probably many other factors. Join Algorithms: Nested Loop Join: Best for small inputs, can be optimized with ordered inner table. Merge Join: Best for medium to large inputs sorted inputs, or an output that needs to be ordered. Hash Join: Best for medium to large inputs, can be parallelized to scale linearly. LINQ Query: DataTable firstTable, secondTable; ... var rows = from firstRow in firstTable.AsEnumerable () join secondRow in secondTable.AsEnumerable () on firstRow.Field<object> (randomObject.Property) equals secondRow.Field<object> (randomObject.Property) select new {firstRow, secondRow}; SQL Query: SELECT * FROM firstTable fT INNER JOIN secondTable sT ON fT.Property = sT.Property Sql Server might use a Nested Loop Join if it knows there are a small number of rows from each table, a merge join if it knows one of the tables has an index, and Hash join if it knows there are a lot of rows on either table and neither has an index. Does Linq choose its algorithm for joins? or does it always use one?

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