Search Results

Search found 32925 results on 1317 pages for 'linq to object'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 31/1317 | < Previous Page | 27 28 29 30 31 32 33 34 35 36 37 38  | Next Page >

  • Search by Letters using LINQ

    - by Biswo
    hi i m using Linq & C# and i want to filter my data as this syntax in Sql Syntax in sql is I hav one table name Customer in which name is field 'Select name from customer where name like 'C%'' can u help to solve this code in Linq

    Read the article

  • .Net Linq - Join together all item of a List

    - by Melursus
    How can I write a Linq expression that select item from a List and join them together ? Example IList<string> data = new List<string>(); data.Add("MyData1"); data.Add("MyData2"); string result = //some linq query... I try data.Select(x => x + ","); //result = "MyData1, MyData2"

    Read the article

  • how to specify literal value in linq union

    - by lowlyintern
    I have the following SQL query, note I want the literal value '0' in the second field in the second SELECT statement from the ItemSale table. How do I express this in LINQ? I get the error message 'Invalid anonymous type member declarator'. SELECT BranchNumber,QuantitySold FROM Department UNION SELECT BranchNumber,0 FROM ItemSale How to express the '0' in LINQ? var unionQuery = (from dept in Department select new { dept.BranchNumber, dept.QuantitySold, }) .Concat(from item in ItemSale select new { item.BranchNumber, 0 });

    Read the article

  • How do linq Last() work?

    - by acidzombie24
    I dont understand how current can be null and last can be an object while last being a LINQ function. I thought last uses GetEnumerator and keeps going until current == null and returns the object. However as you can see the first GetEnumerator().Current is null and last somehow returns an object. How do linq Last() work? var.GetEnumerator().Current var.Last()

    Read the article

  • Data access layer using Linq to SQL

    - by Andrei Tanasescu
    I am building a c# - linq - sql server winforms/asp.net application, accessing a database. I would like my business logic layer to be easily testable, and that means not littering it with Linq database queries everywhere. What design patterns/ best practices are available for the following use cases - inserting/updating a new object - searching for an object - loading a bunch of related data into a sort of "presentation" object that could be displayed by various views ?

    Read the article

  • LINQ - joining multiple lists

    - by kristian
    I've looked at the 101 Linq Samples here but I can't see anything like this in that list. If I'm just not seeing a relevant example there, please link to it. If I have these 3 classes: class Student { int id; string name } class Course { int id, string name } class Enrolment { int studentId; int courseId; } How would I use LINQ to get a list of courses a student is enrolled on? (assume I have an IList of all three classes)

    Read the article

  • Linq to XSD processing

    - by goel
    For Typed Xml to Linq processing ,do i need to download Linq to XSD alpha installer or is it available in VS 2008 ? (I am using VS 2008 Professional edition).

    Read the article

  • Cast problem with LINQ

    - by yigit
    I'm tring to get my product's types to a list with Linq. var types = (from t in NHibernateSession.Linq<Product>() select t.Type).Distinct().ToList<Type>(); return types; But its giving an Unable to cast object of type error '...Domain.Product' to type '...Domain.Type'. Please tell where am I going wrong.

    Read the article

  • Reconciling a new BindingList into a master BindingList using LINQ

    - by Neo
    I have a seemingly simple problem whereby I wish to reconcile two lists so that an 'old' master list is updated by a 'new' list containing updated elements. Elements are denoted by a key property. These are my requirements: All elements in either list that have the same key results in an assignment of that element from the 'new' list over the original element in the 'old' list only if any properties have changed. Any elements in the 'new' list that have keys not in the 'old' list will be added to the 'old' list. Any elements in the 'old' list that have keys not in the 'new' list will be removed from the 'old' list. I found an equivalent problem here - http://stackoverflow.com/questions/161432/ - but it hasn't really been answered properly. So, I came up with an algorithm to iterate through the old and new lists and perform the reconciliation as per the above. Before anyone asks why I'm not just replacing the old list object with the new list object in its entirety, it's for presentation purposes - this is a BindingList bound to a grid on a GUI and I need to prevent refresh artifacts such as blinking, scrollbars moving, etc. So the list object must remain the same, only its updated elements changed. Another thing to note is that the objects in the 'new' list, even if the key is the same and all the properties are the same, are completely different instances to the equivalent objects in the 'old' list, so copying references is not an option. Below is what I've come up with so far - it's a generic extension method for a BindingList. I've put comments in to demonstrate what I'm trying to do. public static class BindingListExtension { public static void Reconcile<T>(this BindingList<T> left, BindingList<T> right, string key) { PropertyInfo piKey = typeof(T).GetProperty(key); // Go through each item in the new list in order to find all updated and new elements foreach (T newObj in right) { // First, find an object in the new list that shares its key with an object in the old list T oldObj = left.First(call => piKey.GetValue(call, null).Equals(piKey.GetValue(newObj, null))); if (oldObj != null) { // An object in each list was found with the same key, so now check to see if any properties have changed and // if any have, then assign the object from the new list over the top of the equivalent element in the old list foreach (PropertyInfo pi in typeof(T).GetProperties()) { if (!pi.GetValue(oldObj, null).Equals(pi.GetValue(newObj, null))) { left[left.IndexOf(oldObj)] = newObj; break; } } } else { // The object in the new list is brand new (has a new key), so add it to the old list left.Add(newObj); } } // Now, go through each item in the old list to find all elements with keys no longer in the new list foreach (T oldObj in left) { // Look for an element in the new list with a key matching an element in the old list if (right.First(call => piKey.GetValue(call, null).Equals(piKey.GetValue(oldObj, null))) == null) { // A matching element cannot be found in the new list, so remove the item from the old list left.Remove(oldObj); } } } } It can be called like this: _oldBindingList.Reconcile(newBindingList, "MyKey") However, I'm looking for perhaps a method of doing the same using LINQ type methods such as GroupJoin<, Join<, Select<, SelectMany<, Intersect<, etc. So far, the problem I've had is that each of these LINQ type methods result in brand new intermediary lists (as a return value) and really, I only want to modify the existing list for all the above reasons. If anyone can help with this, would be most appreciated. If not, no worries, the above method (as it were) will suffice for now. Thanks, Jason

    Read the article

  • spl_object_hash for PHP < 5.2 (unique ID for object instances)

    - by Rowan
    I'm trying to get unique IDs for object instances in PHP 5+. The function, spl_object_hash() is available from PHP 5.2 but I'm wondering if there's a workaround for older versions. There are a couple of functions in the comments on php.net but they're not working for me. The first (simplified): function spl_object_hash($object){ if (is_object($object)){ return md5((string)$object); } return null; } does not work with native objects (such as DOMDocument), and the second: function spl_object_hash($object){ if (is_object($object)){ ob_start(); var_dump($object); $dump = ob_get_contents(); ob_end_clean(); if (preg_match('/^object\(([a-z0-9_]+)\)\#(\d)+/i', $dump, $match)) { return md5($match[1] . $match[2]); } } return null; } looks like it could be a major performance buster! Does anybody have anything up their sleeve?

    Read the article

  • "Attach or Add an entity that is not new...loaded from another DataContext. This is not supported."

    - by sah302
    Similar error as other questions, but not quite the same, I am not trying to attach anything. What I am trying to do is insert a new row into a linking table, specifically UserAccomplishment. Relations are set in LINQ to User and Accomplishment Tables. I have a generic insert function: Public Function insertRow(ByVal entity As ImplementationType) As Boolean If entity IsNot Nothing Then Dim lcfdatacontext As New LCFDataContext() Try lcfdatacontext.GetTable(Of ImplementationType)().InsertOnSubmit(entity) lcfdatacontext.SubmitChanges() lcfdatacontext.Dispose() Return True Catch ex As Exception Return False End Try Else Return False End If End Function If you try and give UserAccomplishment the two appropriate objects this will naturally crap out if either the User or Accomplishment already exist. It only works when both user and accomplishment don't exist. I expected this behavior. What does work is simply giving the userAccomplishment object a user.id and accomplishment.id and populating the rest of the fields. This works but is kind of awkward to use in my app, it would be much easier to simply pass in both objects and have it work out what already exists and what doesn't. Okay so I made the following (please ignore the fact that this is horribly inefficient because I know it is): Public Class UserAccomplishmentDao Inherits EntityDao(Of UserAccomplishment) Public Function insertLinkerObjectRow(ByVal userAccomplishment As UserAccomplishment) Dim insertSuccess As Boolean = False If Not userAccomplishment Is Nothing Then Dim userDao As New UserDao() Dim accomplishmentDao As New AccomplishmentDao() Dim user As New User() Dim accomplishment As New Accomplishment() 'see if either object already exists in db' user = userDao.getOneByValueOfProperty("Id", userAccomplishment.User.Id) accomplishment = accomplishmentDao.getOneByValueOfProperty("Id", userAccomplishment.Accomplishment.Id) If user Is Nothing And accomplishment Is Nothing Then 'neither the user or the accomplishment exist, both are new so insert them both, typical insert' insertSuccess = Me.insertRow(userAccomplishment) ElseIf user Is Nothing And Not accomplishment Is Nothing Then 'user is new, accomplishment is not new, so just insert the user, and the relation in userAccomplishment' Dim userWithExistingAccomplishment As New UserAccomplishment(userAccomplishment.User, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userWithExistingAccomplishment) ElseIf Not user Is Nothing And accomplishment Is Nothing Then 'user is not new, accomplishment is new, so just insert the accomplishment, and the relation in userAccomplishment' Dim existingUserWithAccomplishment As New UserAccomplishment(userAccomplishment.UserId, userAccomplishment.Accomplishment, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(existingUserWithAccomplishment) Else 'both are not new, just add the relation' Dim userAccomplishmentBothExist As New UserAccomplishment(userAccomplishment.User.Id, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userAccomplishmentBothExist) End If End If Return insertSuccess End Function End Class Alright, here I basically check if the supplied user and accomplishment already exists in the db, and if so call an appropriate constructor that will leave whatever already exists empty, but supply the rest of the information so the insert can succeed. However, upon trying an insert: Dim result As Boolean = Me.userAccomplishmentDao.insertLinkerObjectRow(userAccomplishment) In which the user already exists, but the accomplishment does not (the 99% typical scenario) I get the error: "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." I have debugged this multiple times now and am not sure why this is occuring, if either User or Accomplishment exist, I am not including it in the final object to try to insert. So nothing appears to be attempted to be added. Even in debug, upon insert, the object was set to empty. So the accomplishment is new and the user is empty. 1) Why is it still saying that and how can I fix it ..using my current structure 2) Pre-emptive 'use repository pattern answers' - I know this way kind of sucks in general and I should be using the repository pattern. However, I can't use that in the current project because I don't have time to refactor that due to my non existence knowledge of it and time constraints. The usage of the app is going to so small that the inefficient use of datacontext's and what have you won't matter so much. I can refactor it once it's up and running, but for now I just need to 'push through' with my current structure. Edit: I also just tested this when having both already exists, and only insert each object's IDs into the table, that works. So I guess I could manually insert whichever object doesn't exist as a single insert, then put the ids only into the linking table, but I still don't know why when one object exists, and I make it empty, it doens't work.

    Read the article

  • PHP: How do I access child properties from a method in a base object?

    - by Nick
    I'd like for all of my objects to be able to return a JSON string of themselves. So I created a base class for all of my objects to extend, with an AsJSON() method: class BaseObject { public function AsJSON() { $JSON=array(); foreach ($this as $key = $value) { if(is_null($value)) continue; $JSON[$key] = $value; } return json_encode($JSON); } } And then extend my child classes from that: class Package extends BaseObject { ... } So in my code, I expect to do this: $Box = new Package; $Box-SetID('123'); $Box-SetName('12x8x6'); $Box-SetBoxX('12'); $Box-SetBoxY('8'); $Box-SetBoxZ('6'); echo $Box-AsJSON(); But the JSON string it returns only contains the BaseClass's properties, not the child properties. How do I modify my AsJSON() function so that $this refers to the child's properties, not the parent's?

    Read the article

  • Should I be learning Linq, Direct SQL Commands (in .net), EF or other?

    - by Wil
    Basically, I have a very good knowledge of plain old SQL coming from Classic ASP programming. Over the past couple of months, I have been learning C# and today was my first full day at MVC 3 (Razor) which I am loving! I need to get back in to Databases and I know that writing SqlCommand everywhere is obviously outdated (although it is nice I can still do it!). I used to go to a great usergroup as an IT Pro and the developer stuff went completely over my head, however I do remember a few things which kept coming up such as LINQ... However, that was some time ago and now the same people on Twitter are saying how out dated it is. I have tried to do research on both and I am clueless as to what direction I should go in, or when to use one over another (if learning both is a good thing). I am more so confused as I thought EF was a part of the .Net Framework, however, reading through the quick start guide, I had to download a component using Nuget. ... Basically I am out of my depth here and just need some honest advice of where to go!

    Read the article

  • Why "object reference not set to an instance of an object" doesn't tell us which object?

    - by Saeed Neamati
    We're launching a system, and we sometimes get the famous exception NullReferenceException with the message Object reference not set to an instance of an object. However, in a method where we have almost 20 objects, having a log which says an object is null, is really of no use at all. It's like telling you, when you are the security agent of a seminar, that a man among 100 attendees is a terrorist. That's really of no use to you at all. You should get more information, if you want to detect which man is the threatening man. Likewise, if we want to remove the bug, we do need to know which object is null. Now, something has obsessed my mind for several months, and that is: Why .NET doesn't give us the name, or at least the type of the object reference, which is null?. Can't it understand the type from reflection or any other source? Also, what are the best practices to understand which object is null? Should we always test nullability of objects in these contexts manually and log the result? Is there a better way?

    Read the article

  • Use CompiledQuery.Compile to improve LINQ to SQL performance

    - by Michael Freidgeim
    After reading DLinq (Linq to SQL) Performance and in particular Part 4  I had a few questions. If CompiledQuery.Compile gives so much benefits, why not to do it for all Linq To Sql queries? Is any essential disadvantages of compiling all select queries? What are conditions, when compiling makes whose performance, for how much percentage? World be good to have default on application config level or on DBML level to specify are all select queries to be compiled? And the same questions about Entity Framework CompiledQuery Class. However in comments I’ve found answer  of the author ricom 6 Jul 2007 3:08 AM Compiling the query makes it durable. There is no need for this, nor is there any desire, unless you intend to run that same query many times. SQL provides regular select statements, prepared select statements, and stored procedures for a reason.  Linq now has analogs. Also from 10 Tips to Improve your LINQ to SQL Application Performance   If you are using CompiledQuery make sure that you are using it more than once as it is more costly than normal querying for the first time. The resulting function coming as a CompiledQuery is an object, having the SQL statement and the delegate to apply it.  And your delegate has the ability to replace the variables (or parameters) in the resulting query. However I feel that many developers are not informed enough about benefits of Compile. I think that tools like FxCop and Resharper should check the queries  and suggest if compiling is recommended. Related Articles for LINQ to SQL: MSDN How to: Store and Reuse Queries (LINQ to SQL) 10 Tips to Improve your LINQ to SQL Application Performance Related Articles for Entity Framework: MSDN: CompiledQuery Class Exploring the Performance of the ADO.NET Entity Framework - Part 1 Exploring the Performance of the ADO.NET Entity Framework – Part 2 ADO.NET Entity Framework 4.0: Making it fast through Compiled Query

    Read the article

  • Associating an object with another object for GC clearup

    - by thecoop
    Is there any way of associating an object instance (object A) with a second object (object B) in a generalised way, so that when B gets collected A becomes eligable for collection? The same behaviour that would happen if B had an instance variable pointing to A, but without explicitly changing the class definition of B, and being able to do this in a dynamic way? The same sort of effect could be done by using the Component.Disposed event in a funky way, but I don't want to make B disposable EDIT I'm basically creating a cache of objects that are associated with a single 'root' object, and I don't want the cache to be static, as there can be lots of root objects using different caches, so lots of memory will be used up when a root object is no longer used but the cached objects are still around. So, I want a collection of cached objects to be associated with each 'root' object, without changing the root object definition. Sort of like metadata of an extra object reference attached to each root object instance. That way, each collection will get collected when the root object is collected, and not hang around like they would if a static cache was used.

    Read the article

  • LINQ - Select Statement - The null value cannot be assigned to a member with type System.Int32 which

    - by thiag0
    I am trying to achieve the following... _4S.NJB_Request request = (from r in db.NJB_Requests where r.RequestId == referenceId select r).Take(1).SingleOrDefault(); Getting the following exception... Message: The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source) at DAL.SqlDataProvider.MarkNJBPCRequestAsComplete(Int32 referenceId, Int32 processState) I have verified that 'referenceId' does have a value. Anyone know why this would happen in a select statement? Thanks!

    Read the article

  • Linq to SQL and concurrency with Rob Conery repository pattern

    - by David Hall
    I have implemented a DAL using Rob Conery's spin on the repository pattern (from the MVC Storefront project) where I map database objects to domain objects using Linq and use Linq to SQL to actually get the data. This is all working wonderfully giving me the full control over the shape of my domain objects that I want, but I have hit a problem with concurrency that I thought I'd ask about here. I have concurrency working but the solution feels like it might be wrong (just one of those gitchy feelings). The basic pattern is: private MyDataContext _datacontext private Table _tasks; public Repository(MyDataContext datacontext) { _dataContext = datacontext; } public void GetTasks() { _tasks = from t in _dataContext.Tasks; return from t in _tasks select new Domain.Task { Name = t.Name, Id = t.TaskId, Description = t.Description }; } public void SaveTask(Domain.Task task) { Task dbTask = null; // Logic for new tasks omitted... dbTask = (from t in _tasks where t.TaskId == task.Id select t).SingleOrDefault(); dbTask.Description = task.Description, dbTask.Name = task.Name, _dataContext.SubmitChanges(); } So with that implementation I've lost concurrency tracking because of the mapping to the domain task. I get it back by storing the private Table which is my datacontext list of tasks at the time of getting the original task. I then update the tasks from this stored Table and save what I've updated This is working - I get change conflict exceptions raised when there are concurrency violations, just as I want. However, it just screams to me that I've missed a trick. Is there a better way of doing this? I've looked at the .Attach method on the datacontext but that appears to require storing the original version in a similar way to what I'm already doing. I also know that I could avoid all this by doing away with the domain objects and letting the Linq to SQL generated objects all the way up my stack - but I dislike that just as much as I dislike the way I'm handling concurrency.

    Read the article

  • LINQ into SortedList

    - by Chris Simmons
    I'm a complete LINQ newbie, so I don't know if my LINQ is incorrect for what I need to do or if my expectations of performance are too high. I've got a SortedList of objects, keyed by int; SortedList as opposed to SortedDictionary because I'll be populating the collection with pre-sorted data. My task is to find either the exact key or, if there is no exact key, the one with the next higher value. If the search is too high for the list (e.g. highest key is 100, but search for 105), return null. // The structure of this class is unimportant. Just using // it as an illustration. public class CX { public int KEY; public DateTime DT; } static CX getItem(int i, SortedList<int, CX> list) { var items = (from kv in list where kv.Key >= i select kv.Key); if (items.Any()) { return list[items.Min()]; } return null; } Given a list of 50,000 records, calling getItem 500 times takes about a second and a half. Calling it 50,000 times takes over 2 minutes. This performance seems very poor. Is my LINQ bad? Am I expecting too much? Should I be rolling my own binary search function?

    Read the article

  • Delphi Prism and LINQ to SQL / Entity Framework

    - by Vegar
    I have found many posts and examples of using LINQ-syntax in Delphi Prism (Oxygene), but I have never found anything on LINQ to SQL or Entity Framework. Is it possible to use LINQ to SQL or Entity Framework together with Prism? Where can I found such an example? Update: Olaf is giving an answer through his blog The question is now if any visual tools and code generation is provided, or if everything must be done by hand... Second update: Olaf has answered the tool/code generation-question in a comment on his site: The class designer is there, but there is no Pascal code gen. According to marc hoffman that is currently not on their list. For now you have to live with manual mapping. I guess, if you had Visual Studio (not just the VS shell), that you could add a C# library project to your solution, reference that from your Prism project. Then create the Table-Class mapping in the C# project using the visual designer. Maybe somewhat ugly, but possibly the key to get the Designer + CodeGen integrated into Prism. Who cares what language is used for the mapping . I will say this is a 1 - 0 to c# vs prism. If I did not care which language is used for the mapping - why should I care about which language is used for the rest?

    Read the article

  • LINQ-to-SQL: Could not find key member 'x' of key 'x' on type 'y'

    - by Austin Hyde
    I am trying to connect my application to a SQLite database with LINQ-to-SQL, and so far everything has worked fine. The only hitch was that the SQLite provider I am using does not support code generation (unless I was doing something wrong), so I manually coded the 4 tables in the DB. The solution builds properly, but will not run, giving me the error message Could not find key member 'ItemType_Id' of key 'ItemType_Id' on type 'Item'. The key may be wrong or the field or property on 'Item' has changed names. I have checked and double checked spellings and field names on the database and in the attribute mappings, but could not find any problems. The SQL for the table looks like this: CREATE TABLE [Items] ( [Id] integer PRIMARY KEY AUTOINCREMENT NOT NULL, [Name] text NOT NULL, [ItemType_Id] integer NOT NULL ); And my mapping code: [Table(Name="Items")] class Item { // [snip] [Column(Name = "Id", IsPrimaryKey=true, IsDbGenerated=true)] public int Id { get; set; } // [snip] [Column(Name="ItemType_Id")] public int ItemTypeId { get; set; } [Association(Storage = "_itemType", ThisKey = "ItemType_Id")] public ItemType ItemType { get { return _itemType.Entity; } set { _itemType.Entity = value; } } private EntityRef<ItemType> _itemType; // [snip] } This is really my first excursion into LINQ-to-SQL, and am learning as I go, but I cannot seem to get past this seeming simple problem. Why cannot LINQ see my association?

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 27 28 29 30 31 32 33 34 35 36 37 38  | Next Page >