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  • Simplify Your Code with LINQ

    - by dwahlin
    I’m a big fan of LINQ and use it wherever I can to minimize code and make applications easier to maintain overall. I was going through a code file today refactoring it based on suggestions provided by Resharper and came across the following method: private List<string> FilterTokens(List<string> tokens) { var cleanedTokens = new List<string>(); for (int i = 0; i < tokens.Count; i++) { string token = tokens[i]; if (token != null) { cleanedTokens.Add(token); } } return cleanedTokens; }   In looking through the code I didn’t see anything wrong but Resharper was suggesting that I convert it to a LINQ expression: In thinking about it more the suggestion made complete sense because I simply wanted to add all non-null token values into a List<string> anyway. After following through with the Resharper suggestion the code changed to the following. Much, much cleaner and yet another example of why LINQ (and Resharper) rules: private List<string> FilterTokens(IEnumerable<string> tokens) { return tokens.Where(token => token != null).ToList(); }

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  • Take,Skip and Reverse Operator in Linq

    - by Jalpesh P. Vadgama
    I have found three more new operators in Linq which is use full in day to day programming stuff. Take,Skip and Reverse. Here are explanation of operators how it works. Take Operator: Take operator will return first N number of element from entities. Skip Operator: Skip operator will skip N number of element from entities and then return remaining elements as a result. Reverse Operator: As name suggest it will reverse order of elements of entities. Here is the examples of operators where i have taken simple string array to demonstrate that. C#, using GeSHi 1.0.8.6 using System; using System.Collections.Generic; using System.Linq; using System.Text;     namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             string[] a = { "a", "b", "c", "d" };                           Console.WriteLine("Take Example");             var TkResult = a.Take(2);             foreach (string s in TkResult)             {                 Console.WriteLine(s);             }               Console.WriteLine("Skip Example");             var SkResult = a.Skip(2);             foreach (string s in SkResult)             {                 Console.WriteLine(s);             }               Console.WriteLine("Reverse Example");             var RvResult = a.Reverse();             foreach (string s in RvResult)             {                 Console.WriteLine(s);             }                       }     } } Parsed in 0.020 seconds at 44.65 KB/s Here is the output as expected. hope this will help you.. Technorati Tags: Linq,Linq-To-Sql,ASP.NET,C#.NET

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  • Running Objects – Associations and Relationships

    - by edurdias
    After the introduction to the Running Objects with the tutorial Movie Database in 2 Minutes (available here), I would like to demonstrate how Running Objects interprets the Associations where we will cover: Direct Association – A reference to another complex object. Aggregation – A collection of another complex object. For those coming with a database perspective, by demonstrating these associations we will also exemplify the underline relationships such as 1 to Many and Many to Many relationships...(read more)

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  • Problem with Mapping Linq-to-Sql on different Types

    - by csharpnoob
    Hi, maybe someone can help. I want to have on mapped Linq-Class different Datatype. This is working: private System.Nullable<short> _deleted = 1; [Column(Storage = "_deleted", Name = "deleted", DbType = "SmallInt", CanBeNull = true)] public System.Nullable<short> deleted { get { return this._deleted; } set { this._deleted = value; } } Sure thing. But no when i want to place some logic for boolean, like this: private System.Nullable<short> _deleted = 1; [Column(Storage = "_deleted", Name = "deleted", DbType = "SmallInt", CanBeNull = true)] public bool deleted { get { if (this._deleted == 1) { return true; } return false; } set { if(value == true) { this._deleted = (short)1; }else { this._deleted = (short)0; } } } I get always runtime error: [TypeLoadException: GenericArguments[2], "System.Nullable`1[System.Int16]", on 'System.Data.Linq.Mapping.PropertyAccessor+Accessor`3[T,V,V2]' violates the constraint of type parameter 'V2'.] I can't change the database to bit.. I need to have casting in mapping class.

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  • c# linq to xml to list

    - by WtFudgE
    I was wondering if there is a way to get a list of results into a list with linq to xml. If I would have the following xml for example: <?xml version="1.0"?> <Sports xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <SportPages> <SportPage type="test"> <LinkPage> <IDList> <string>1</string> <string>2</string> </IDList> </LinkPage> </SportPage> </SportPages> </Sports> How could I get a list of strings from the IDList? I'm fairly new to linq to xml so I just tried some stuff out, I'm currently at this point: var IDs = from sportpage in xDoc.Descendants("SportPages").Descendants("SportPage") where sportpage.Attribute("type").Value == "Karate" select new { ID = sportpage.Element("LinkPage").Element("IDList").Elements("string") }; But the var is to chaotic to read decently. Isn't there a way I could just get a list of strings from this? Thanks

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  • ASP MVC C#: LINQ Foreign Key Constraint conflicts

    - by wh0emPah
    I'm having a problem with LINQ. I have 2 tables (Parent-child relation) Table1: Events (EventID, Description) Table2: Groups (GroupID, EventID(FK), Description) Now i want to create an Event an and a child. Event e = new Event(); e.Description = "test"; Datacontext.Events.InsertOnSubmit(event) Group g = new Group(); g.Description = "test2"; g.EventID = e.EventID; Datacontext.Groups.InsertOnSubmit(g); Datacontext.SubmitChanges(); When i debug, i can see that after inserting the event. the EventID has gotten a new value (auto increment). But when Datacontext.SubmitChanges(); gets called. I get the following exception "The INSERT statement conflicted with the FOREIGN KEY constraint ... I know this can be solved by creating a relation in the LINQ diagram between Events and groups. And then setting the entity itself. But i don't want to load the events everytime i ask a list of groups. All i need is some way that when inserting the group fails, the event insert won't be comitted in the database. Sorry if this is a bit unclear, My english isn't really good. Thanks in advance!

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  • LINQ self referencing query

    - by Chris
    I have the following SQL query: select p1.[id], p1.[useraccountid], p1.[subject], p1.[message], p1.[views], p1.[parentid], case when p2.[created] is null then p1.[created] else p2.[created] end as LastUpdate from forumposts p1 left join ( select parentid, max(created) as [created] from forumposts group by parentid ) p2 on p2.parentid = p1.id where p1.[parentid] is null order by LastUpdate desc Using the following class: public class ForumPost : PersistedObject { public int Views { get; set; } public string Message { get; set; } public string Subject { get; set; } public ForumPost Parent { get; set; } public UserAccount UserAccount { get; set; } public IList<ForumPost> Replies { get; set; } } How would I replicate such a query in LINQ? I've tried several variations, but I seem unable to get the correct join syntax. Is this simply a case of a query that is too complicated for LINQ? Can it be done using nested queries some how? The purpose of the query is to find the most recently updated posts i.e. replying to a post would bump it to the top of the list. Replies are defined by the ParentID column, which is self-referencing.

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  • Tracking Down a Stack Overflow in My Linq Query

    - by Lazarus
    I've written the following Linq query: IQueryable<ISOCountry> entries = (from e in competitorRepository.Competitors join c in countries on e.countryID equals c.isoCountryCode where !e.Deleted orderby c.isoCountryCode select new ISOCountry() { isoCountryCode = e.countryID, Name = c.Name }).Distinct(); The objective is to retrieve a list of the countries represented by the competitors found in the system. 'countries' is an array of ISOCountry objects explicitly created and returned as an IQueryable (ISOCountry is an object of just two strings, isoCountryCode and Name). Competitors is an IQueryable which is bound to a database table through Linq2SQL though I created the objects from scratch and used the Linq data mapping decorators. For some reason this query causes a stack overflow when the system tries to execute it. I've no idea why, I've tried trimming the Distinct, returning an anonymous type of the two strings, using 'select c', all result in the overflow. The e.CountryID value is populated from a dropdown that was in itself populated from the IQueryable so I know the values are appropriate but even if not I wouldn't expect a stack overflow. Can anyone explain why the overflow is occurring or give good speculation as to why it might be happening? EDIT As requested, code for ISOCountry: public class ISOCountry { public string isoCountryCode { get; set; } public string Name { get; set; } }

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  • LINQ to XML via C#

    - by user70192
    Hello, I'm new to LINQ. I understand it's purpose. But I can't quite figure it out. I have an XML set that looks like the following: <Results> <Result> <ID>1</ID> <Name>John Smith</Name> <EmailAddress>[email protected]</EmailAddress> </Result> <Result> <ID>2</ID> <Name>Bill Young</Name> <EmailAddress>[email protected]</EmailAddress> </Result> </Results> I have loaded this XML into an XDocument as such: string xmlText = GetXML(); XDocument xml = XDocument.Parse(xmlText); Now, I'm trying to get the results into POCO format. In an effort to do this, I'm currently using: var objects = from results in xml.Descendants("Results") select new Results // I'm stuck How do I get a collection of Result elements via LINQ? I'm particularly confused about navigating the XML structure at this point in my code. Thank you!

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  • Getting values from DataGridView back to XDocument (using LINQ-to-XML)

    - by Pretzel
    Learning LINQ has been a lot of fun so far, but despite reading a couple books and a bunch of online resources on the topic, I still feel like a total n00b. Recently, I just learned that if my query returns an Anonymous type, the DataGridView I'm populating will be ReadOnly (because, apparently Anonymous types are ReadOnly.) Right now, I'm trying to figure out the easiest way to: Get a subset of data from an XML file into a DataGridView, Allow the user to edit said data, Stick the changed data back into the XML file. So far I have Steps 1 and 2 figured out: public class Container { public string Id { get; set; } public string Barcode { get; set; } public float Quantity { get; set; } } // For use with the Distinct() operator public class ContainerComparer : IEqualityComparer<Container> { public bool Equals(Container x, Container y) { return x.Id == y.Id; } public int GetHashCode(Container obj) { return obj.Id.GetHashCode(); } } var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new Container { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(new ContainerComparer()); dataGridView1.DataSource = barcodes.ToList(); This works great at getting the data I want from the XML into the DataGridView so that the user has a way to manipulate the values. Upon doing a Step-thru trace of my code, I'm finding that the changes to the values made in DataGridView are not bound to the XDocument object and as such, do not propagate back. How do we take care of Step 3? (getting the data back to the XML) Is it possible to Bind the XML directly to the DataGridView? Or do I have to write another LINQ statement to get the data from the DGV back to the XDocument? Suggstions?

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  • Linq join with an inner collection

    - by bronze
    Hi, I am trying a LINQ to Object query on 2 collections Customer.Orders Branches.Pending.Orders (Collection within a collection) I want to output each branch which is yet to deliver any order of the customer. var match = from order in customer.Orders join branch in Branches on order equals branch.Pending.Orders select branch; This does not work, I get : The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'GroupJoin'. From my search, I think this is because Order or collection of Orders does not implement equals. If this query worked, it will still be wrong, as it will return a branch if the customer's and pending orders match exactly. I want a result if any of the order matches. I am learning Linq, and looking for a approach to address such issues, rather than the solution itself. I would have done this in SQL like this; SELECT b.branch_name from Customers c, Branches b, Orders o WHERE c.customer_id = o.customer_id AND o.branch_id = b.branch_id AND c.customer_id = 'my customer' AND o.order_status = 'pending'

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  • Linq is returning too many results when joined

    - by KallDrexx
    In my schema I have two database tables. relationships and relationship_memberships. I am attempting to retrieve all the entries from the relationship table that have a specific member in it, thus having to join it with the relationship_memberships table. I have the following method in my business object: public IList<DBMappings.relationships> GetRelationshipsByObjectId(int objId) { var results = from r in _context.Repository<DBMappings.relationships>() join m in _context.Repository<DBMappings.relationship_memberships>() on r.rel_id equals m.rel_id where m.obj_id == objId select r; return results.ToList<DBMappings.relationships>(); } _Context is my generic repository using code based on the code outlined here. The problem is I have 3 records in the relationships table, and 3 records in the memberships table, each membership tied to a different relationship. 2 membership records have an obj_id value of 2 and the other is 3. I am trying to retrieve a list of all relationships related to object #2. When this linq runs, _context.Repository<DBMappings.relationships>() returns the correct 3 records and _context.Repository<DBMappings.relationship_memberships>() returns 3 records. However, when the results.ToList() executes, the resulting list has 2 issues: 1) The resulting list contains 6 records, all of type DBMappings.relationships(). Upon further inspection there are 2 for each real relationship record, both are an exact copy of each other. 2) All relationships are returned, even if m.obj_id == 3, even though objId variable is correctly passed in as 2. Can anyone see what's going on because I've spent 2 days looking at this code and I am unable to understand what is wrong. I have joins in other linq queries that seem to be working great, and my unit tests show that they are still working, so I must be doing something wrong with this. It seems like I need an extra pair of eyes on this one :)

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  • Using conditionals in Linq Programatically

    - by Mike B
    I was just reading a recent question on using conditionals in Linq and it reminded me of an issue I have not been able to resolve. When building Linq to SQL queries programatically how can this be done when the number of conditionals is not known until runtime? For instance in the code below the first clause creates an IQueryable that, if executed, would select all the tasks (called issues) in the database, the 2nd clause will refine that to just issues assigned to one department if one has been selected in a combobox (Which has it's selected item bound to the departmentToShow property). How could I do this using the selectedItems collection instead? IQueryable<Issue> issuesQuery; // Will select all tasks issuesQuery = from i in db.Issues orderby i.IssDueDate, i.IssUrgency select i; // Filters out all other Departments if one is selected if (departmentToShow != "All") { issuesQuery = from i in issuesQuery where i.IssDepartment == departmentToShow select i; } By the way, the above code is simplified, in the actual code there are about a dozen clauses that refine the query based on the users search and filter settings.

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  • EF/LINQ: Where() against a property of a subtype

    - by ladenedge
    I have a set of POCOs, all of which implement the following simple interface: interface IIdObject { int Id { get; set; } } A subset of these POCOs implement this additional interface: interface IDeletableObject : IIdObject { bool IsDeleted { get; set; } } I have a repository hierarchy that looks something like this: IRepository<T <: BasicRepository<T <: ValidatingRepository<T (where T is IIdObject) I'm trying to add a FilteringRepository to the hierarchy such that all of the POCOs that implement IDeletableObject have a Where(p => p.IsDeleted == false) filter applied before any other queries take place. My goal is to avoid duplicating the hierarchy solely for IDeletableObjects. My first attempt looked like this: public override IQueryable<T> Query() { return base.Query().Where(t => ((IDeletableObject)t).IsDeleted == false); } This works well with LINQ to Objects, but when I switch to an EF backend I get: "LINQ to Entities only supports casting Entity Data Model primitive types." I went on to try some fancier parameterized solutions, but they ultimately failed because I couldn't make T covariant in the following case for some reason I don't quite understand: interface IQueryFilter<out T> // error { Expression<Func<T, bool>> GetFilter(); } I'd be happy to go into more detail on my more complicated solutions if it would help, but I think I'll stop here for now in hope that someone might have an idea for me to try. Thanks very much in advance!

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  • Delaying LINQ to SQL Select Query Execution

    - by Maxim Z.
    I'm building an ASP.NET MVC site that uses LINQ to SQL. In my search method that has some required and some optional parameters, I want to build a LINQ query while testing for the existence of those optional parameters. Here's what I'm currently thinking: using(var db = new DBDataContext()) { IQueryable<Listing> query = null; //Handle required parameter query = db.Listings.Where(l => l.Lat >= form.bounds.extent1.latitude && l.Lat <= form.bounds.extent2.latitude); //Handle optional parameter if (numStars != null) query = query.Where(l => l.Stars == (int)numStars); //Other parameters... //Execute query (does this happen here?) var result = query.ToList(); //Process query... Will this implementation "bundle" the where clauses and then execute the bundled query? If not, how should I implement this feature? Also, is there anything else that I can improve? Thanks in advance.

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  • LINQ to objects: Is there

    - by Charles
    I cannot seem to find a way to have LINQ return the value from a specified accessor. I know the name of the accessors for each object, but am unsure if it is possible to pass the requested accessor as a variable or otherwise achieve the desired refactoring. Consider the following code snippet: // "value" is some object with accessors like: format, channels, language row = new List<String> { String.Join(innerSeparator, (from item in myObject.Audio orderby item.Key ascending select item.Value.format).ToArray()), String.Join(innerSeparator, (from item in myObject.Audio orderby item.Key ascending select item.Value.channels).ToArray()), String.Join(innerSeparator, (from item in myObject.Audio orderby item.Key ascending select item.Value.language).ToArray()), // ... } I'd like to refactor this into a method that uses the specified accessor, or perhaps pass a delegate, though I don't see how that could work. string niceRefactor(myObj myObject, string /* or whatever type */ ____ACCESSOR) { return String.Join(innerSeparator, (from item in myObject.Audio orderby item.Key ascending select item.Value.____ACCESSOR).ToArray()); } I have written a decent amount of C#, but am still new to the magic of LINQ. Is this the right approach? How would you refactor this?

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  • LINQ to SQL: Reusable expression for property?

    - by coenvdwel
    Pardon me for being unable to phrase the title more exact. Basically, I have three LINQ objects linked to tables. One is Product, the other is Company and the last is a mapping table Mapping to store what Company sells which products and by which ID this Company refers to this Product. I am now retrieving a list of products as follows: var options = new DataLoadOptions(); options.LoadWith<Product>(p => p.Mappings); context.LoadOptions = options; var products = ( from p in context.Products select new { ProductID = p.ProductID, //BackendProductID = p.BackendProductID, BackendProductID = (p.Mappings.Count == 0) ? "None" : (p.Mappings.Count > 1) ? "Multiple" : p.Mappings.First().BackendProductID, Description = p.Description } ).ToList(); This does a single query retrieving the information I want. But I want to be able to move the logic behind the BackendProductID into the LINQ object so I can use the commented line instead of the annoyingly nested ternary operator statements for neatness and re-usability. So I added the following property to the Product object: public string BackendProductID { get { if (Mappings.Count == 0) return "None"; if (Mappings.Count > 1) return "Multiple"; return Mappings.First().BackendProductID; } } The list is still the same, but it now does a query for every single Product to get it's BackendProductID. The code is neater and re-usable, but the performance now is terrible. What I need is some kind of Expression or Delegate but I couldn't get my head around writing one. It always ended up querying for every single product, still. Any help would be appreciated!

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  • Linq generic Expression in query on "element" or on IQueryable (multiple use)

    - by Bogdan Maxim
    Hi, I have the following expression public static Expression<Func<T, bool>> JoinByDateCheck<T>(T entity, DateTime dateToCheck) where T : IDateInterval { return (entityToJoin) => entityToJoin.FromDate.Date <= dateToCheck.Date && (entityToJoin.ToDate == null || entityToJoin.ToDate.Value.Date >= dateToCheck.Date); } IDateInterval interface is defined like this: interface IDateInterval { DateTime FromDate {get;} DateTime? ToDate {get;} } and i need to apply it in a few ways: (1) Query on Linq2Sql Table: var q1 = from e in intervalTable where FunctionThatCallsJoinByDateCheck(e, constantDateTime) select e; or something like this: intervalTable.Where(FunctionThatCallsJoinByDateCheck(e, constantDateTime)) (2) I need to use it in some table joins (as linq2sql doesn't provide comparative join): var q2 = from e1 in t1 join e2 in t2 on e1.FK == e2.PK where OtherFunctionThatCallsJoinByDateCheck(e2, e1.FromDate) or var q2 = from e1 in t1 from e2 in t2 where e1.FK == e2.PK && OtherFunctionThatCallsJoinByDateCheck(e2, e1.FromDate) (3) I need to use it in some queries like this: var q3 = from e in intervalTable.FilterFunctionThatCallsJoinByDateCheck(constantDate); Dynamic linq is not something that I can use, so I have to stick to plain linq. Thank you Clarification: Initially I had just the last method (FilterFunctionThatCallsJoinByDateCheck(this IQueryable<IDateInterval> entities, DateTime dateConstant) ) that contained the code from the expression. The problem is that I get a SQL Translate exception if I write the code in a method and call it like that. All I want is to extend the use of this function to the where clause (see the second query in point 2)

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  • LINQ to SQL Queries odd Materialization

    - by ptoinson
    I ran across an interesting Linq to SQL, uh, feature, the other day. Perhaps someone can give me a logical explanation for the reasoning behind the results. Take the code below as my example which utilizes the AdventureWorks database setup in a Linq to SQL DataContext. This is a clip from my unit test. The resulting customer returned from a call to both CustomerQuery_Test_01() and CustomerQuery_Test_02() is the same. However, the query executed on the SQLServer are different is a major way. The method CustomerQuery_Test_01 us causing the entire Customer table to be materialized, which the call to CustomerQuery_Test_02 is only causing the single customer to be materialized. The resulting SQL Queries are at the bottom of this post. Anyone have a good reason for this? To me, it was highly non-intuitive. protected virtual Customer GetByPrimaryKey(Func<Customer, bool> keySelection) { AdventureWorksDataContext context = new AdventureWorksDataContext(); return (from r in context.Customers select r).SingleOrDefault(keySelection); } [TestMethod] public void CustomerQuery_Test_01() { Customer customer = GetByPrimaryKey(c => c.CustomerID == 2); } [TestMethod] public void CustomerQuery_Test_02() { AdventureWorksDataContext context = new AdventureWorksDataContext(); Customer customer = (from r in context.Customers select r).SingleOrDefault(c => c.CustomerID == 2); } Query for CustomerQuery_Test_01 (notice the lack of a where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] Query for CustomerQuery_Test_02 (notice the where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] WHERE [t0].[CustomerID] = @p0

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  • Union,Except and Intersect operator in Linq

    - by Jalpesh P. Vadgama
    While developing a windows service using Linq-To-SQL i was in need of something that will intersect the two list and return a list with the result. After searching on net i have found three great use full operators in Linq Union,Except and Intersect. Here are explanation of each operator. Union Operator: Union operator will combine elements of both entity and return result as third new entities. Except Operator: Except operator will remove elements of first entities which elements are there in second entities and will return as third new entities. Intersect Operator: As name suggest it will return common elements of both entities and return result as new entities. Let’s take a simple console application as  a example where i have used two string array and applied the three operator one by one and print the result using Console.Writeline. Here is the code for that. C#, using GeSHi 1.0.8.6 using System; using System.Collections.Generic; using System.Linq; using System.Text;     namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             string[] a = { "a", "b", "c", "d" };             string[] b = { "d","e","f","g"};               var UnResult = a.Union(b);             Console.WriteLine("Union Result");               foreach (string s in UnResult)             {                 Console.WriteLine(s);                          }               var ExResult = a.Except(b);             Console.WriteLine("Except Result");             foreach (string s in ExResult)             {                 Console.WriteLine(s);             }               var InResult = a.Intersect(b);             Console.WriteLine("Intersect Result");             foreach (string s in InResult)             {                 Console.WriteLine(s);             }             Console.ReadLine();                        }          } }   Parsed in 0.022 seconds at 45.54 KB/s Here is the output of console application as Expected. Hope this will help you.. Technorati Tags: Linq,Except,InterSect,Union,C#

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  • Using set operation in LINQ

    - by vik20000in
    There are many set operation that are required to be performed while working with any kind of data. This can be done very easily with the help of LINQ methods available for this functionality. Below are some of the examples of the set operation with LINQ. Finding distinct values in the set of data. We can use the distinct method to find out distinct values in a given list.     int[] factorsOf300 = { 2, 2, 3, 5, 5 };     var uniqueFactors = factorsOf300.Distinct(); We can also use the set operation of UNION with the help of UNION method in the LINQ. The Union method takes another collection as a parameter and returns the distinct union values in  both the list. Below is an example.     int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };    int[] numbersB = { 1, 3, 5, 7, 8 };    var uniqueNumbers = numbersA.Union(numbersB); We can also get the set operation of INTERSECT with the help of the INTERSECT method. Below is an example.     int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };     int[] numbersB = { 1, 3, 5, 7, 8 };         var commonNumbers = numbersA.Intersect(numbersB);  We can also find the difference between the 2 sets of data with the help of except method.      int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };     int[] numbersB = { 1, 3, 5, 7, 8 };         IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB);  Vikram

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  • Linq to SQL Lazy Loading in ASP.Net applications

    - by nikolaosk
    In this post I would like to talk about LINQ to SQL and its native lazy loading functionality. I will show you how you can change this behavior. We will create a simple ASP.Net application to demonstrate this. I have seen a lot of people struggling with performance issues. That is mostly due to the lack of knowledge of how LINQ internally works.Imagine that we have two tables Products and Suppliers (Northwind database). There is one to many relationship between those tables-entities. One supplier...(read more)

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  • Flattening a Jagged Array with LINQ

    - by PSteele
    Today I had to flatten a jagged array.  In my case, it was a string[][] and I needed to make sure every single string contained in that jagged array was set to something (non-null and non-empty).  LINQ made the flattening very easy.  In fact, I ended up making a generic version that I could use to flatten any type of jagged array (assuming it's a T[][]): private static IEnumerable<T> Flatten<T>(IEnumerable<T[]> data) { return from r in data from c in r select c; } Then, checking to make sure the data was valid, was easy: var flattened = Flatten(data); bool isValid = !flattened.Any(s => String.IsNullOrEmpty(s)); You could even use method grouping and reduce the validation to: bool isValid = !flattened.Any(String.IsNullOrEmpty); Technorati Tags: .NET,LINQ,Jagged Array

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  • LINQ Style preference

    - by Erin
    I have come to use LINQ in my every day programming a lot. In fact, I rarely, if ever, use an explicit loop. I have, however, found that I don't use the SQL like syntax anymore. I just use the extension functions. So rather then saying: from x in y select datatransform where filter I use: x.Where(c => filter).Select(c => datatransform) Which style of LINQ do you prefer and what are others on your team are comfortable with?

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  • Business Objects - Containers or functional?

    - by Walter
    Where I work, we've gone back and forth on this subject a number of times and are looking for a sanity check. Here's the question: Should Business Objects be data containers (more like DTOs) or should they also contain logic that can perform some functionality on that object. Example - Take a customer object, it probably contains some common properties (Name, Id, etc), should that customer object also include functions (Save, Calc, etc.)? One line of reasoning says separate the object from the functionality (single responsibility principal) and put the functionality in a Business Logic layer or object. The other line of reasoning says, no, if I have a customer object I just want to call Customer.Save and be done with it. Why do I need to know about how to save a customer if I'm consuming the object? Our last two projects have had the objects separated from the functionality, but the debate has been raised again on a new project. Which makes more sense? EDIT These results are very similar to our debates. One vote to one side or another completely changes the direction. Does anyone else want to add their 2 cents? EDIT Eventhough the answer sampling is small, it appears that the majority believe that functionality in a business object is acceptable as long as it is simple but persistence is best placed in a separate class/layer. We'll give this a try. Thanks for everyone's input...

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