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  • retrieving documents from sharepoint via web services using jquery

    - by femi
    Hi, I am trying to develop a mobile application which can interact with a MOSS Site via web services. i expect it to be be able to; 1) retrieve documents (pdf, doc, docx, excel) 2) retrieve reporting services reports in a PDF or excel form. i will be using either phonegap or rhomobile to develop this app and i know that i can consume web services using jquery. My question revolves around MOSS Web Services Security. How will i handle authentication? Thanks

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  • WCF RIA Services Silverlight 3.0

    - by John
    Hi, I have downloaded WCF RIA Services Beta from the following website: WCF RIA Services Beta for Visual Studio 2008 SP1 http://www.microsoft.com/downloads/details.aspx?FamilyID=76bb3a07-3846-4564-b0c3-27972bcaabce&displaylang=en#filelist But I am unable to add a reference to the following assembly : system.Windows.Ria.Data I searched at the downloaded location c:\Program files\Microsoft SDK's\RIA Services but i am unable to find this dll. Would appreciate if you could point me what I am missing here.

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  • ASP.NET MVC ,Maintaining Model State between Ajax requests

    - by Podders
    problem: On first full page request, my controller invokes an applicationServices Layer (Web Service Proxy to my business tier) in order to populate a collection of current services that is stored in my own controller base class property. This is then to be displayed within a view. Everything within the context of that controller has access to this "Services Collection". Now when i make further calls to the same action method via an AJAX Call, i obviously hitt a different instance of that controller meaning my services collection is empty. So other than re-getting the whole collection again, where would i store this collection so it gets persisted between ajax requests? Should i persist it as a seperate DomainModel Object, Session object?....as ViewData is not working for me obv. Excuse my MVC ignorance :) Any help would be greatly appreciated :)

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  • Slow performance of System.Math library in .NET4/VS2010

    - by Niranjan
    My application compiled in .NET 4 seems to be performing really slow compared to .NET 3.5. When I did the performance analysis, I found out that the System.Math libraries in VS2010/.NET 4 have slowed down considerably. Any explanation to this? Has anyone else come across this or am I the only one seeing this? Thanks, Niranjan

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  • Consuming Web Services in Netbeans

    - by Seven
    Hi. I've setup a project in Netbeans 6.5 with some web services that I've created myself and some web services that I've imported from WSDL files. I've setup a couple of desktop application through Netbeans in order to consume these web services. I'm not too sure where to go from here. I have the GUI setup but not sure how to reference the web services so they can be consumed. I was wondering would anybody be able to guide me through this process or point me in the direction of a relevant tutorial. I'd also like to learn how to consume a web service through a JSP (also created in Netbeans) if possible. Thanks.

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  • reporting services 2005 instance

    - by niao
    Greetings, I have Reporting Services Installed on my computer. It was installed previously by other developer. However I cannot access reporting services instance on my localhost. When I open Reporting Services Configuration the error returned is: no report servers were found on the specified machine How can I add/restore this instance?

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  • what is session and session variables ? Plz guide

    - by haansi
    hello, I am new to asp.net Can you please guide me what is session and session variables ? Please I don't need a comparision of asp session and asp.net session because I don't know anything about asp. I have saw many articles on types of session as well. But still I cant understand erectly what is session and what are session variables in asp.net ? Please guide me. thanks

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  • Upgrade from .NET 2.0 to .NET 3.5 problems

    - by Bashir Magomedov
    I’m trying to upgrade our solution from VS2005 .NET 2.0 to VS2008 .NET 3.5. I converted the solution using VS2008 conversion wizard. All the projects (about 50) remained targeting to .NET Framework 2.0., moreover if I’m changing target framework manually for one of the projects, all referenced dll (i.e. System, System.Core, System.Data, etc. are still pointing to Framework 2.0. The only way to completely change targeting framework I found is to remove these references and refer them again using proper version of framework. Doing it manually is not best choice I think. 50 projects ~ 10 references each ~ 0.5 minutes for changing each reference is about 5 hours to complete. Am I missing something? Are there any other ways of converting full solution from .NET 2.0 to .NET 3.5? Thank you.

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  • SQL Server 2005 Reporting Services (x64) on Windows 2K8 -> CleanCurrentUserName() not found

    - by Steven Pardo
    I have installed SQL Server 2005 three times now on the same box. I cleaned up registry settings, files, you name it. All along I have been trying to install SQL Server 2005 Database and Reporting Services (x64) on a Windows 2008 Server. I have also applied the SP3 patch. Installing and Restarting the Server at every point. I have installed multiple instances (SQLDEV64, SQLQA64, SQLSTAGE64) of the Database and Reporting Services. I started to go through the Reporting Services Configuration manager, installing the Reporting Database along with setting up IIS. When I go test the website I get the following and there lies my question. How can I get around this error? http://localhost/reportserver Reporting Services Error -------------------------------------------------------------------------------- An internal error occurred on the report server. See the error log for more details. (rsInternalError) Method not found: 'Void Microsoft.ReportingServices.Diagnostics.UserUtil.CleanCurrentUserName()'. -------------------------------------------------------------------------------- SQL Server Reporting Services Any help would be greatly appreciated.

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  • How to handle concurrency control in dynamic data?

    - by Andrew
    I've been quite impressed with dynamic data and how easy and quick it is to get a simple site up and running. I'm planning on using it for a simple internal HR admin site for registering people's skills/degrees/etc. I've been watching the intro videos at www.asp.net/dynamicdata and one thing they never mention is how to handle concurrency control. It seems that DD does not handle it right out of the box (unless there is some setting I haven't seen) as I manually generated a change conflict exception and the app failed without any user friendly message. Anybody know if DD handles it out of the box? Or do you have to somehow build it into the site?

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  • ASP.NET Dynamic Data Browser Compatibility

    - by Petras
    Could any experienced users of Dynamic Data comment on whether there are issues with it in: Internet Explorer 6 Safari Chrome Opera We are looking to use it on a public facing website and good old IE6 has many important users in government departments and large companies so it has to work there. The other browsers could also become an issue.

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  • Checking only "Automatic" services with powershell.

    - by Lee
    I've seen lots of scripts out there for manually stopping/starting services in a list, but how can I generate that list programatically of -just- the automatic services. I want to script some reboots, and am looking for a way to verify that everything did in fact start up correctly for any services that were supposed to.

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  • Running Services.msc as a different User C#

    - by Simon Mark Smith
    Hi, I have a requirement to create a simple windows forms application that allows an admin user to manage the Services on remote servers. We don't want to give the admins the usernames and passwords to the servers so these will be encrypted and stored in a database. My question is whether or not it is possible to spawn a Services.msc window when impersonating one of the users stored within the database? I have looked at the ProcessStartInfo class but because Services.msc is not an executable it does not seem to like executing this. Any ideas on a simple way of doing the actual impersonation and loading of Services.msc - say off a button click? Thanks

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  • Fast data structure for small sets

    - by thr
    I'm in need for a data structure that can handle small sets (10-20 strings, at most 50, of varying length) very fast. False positives is ok, but false negatives are not. The last requirement makes bloom filters seem like a good fit, but I'm not sure about their speed, any other recommendations?

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  • Web service URL being overwritten with localhost

    - by Jay Heavner
    I have a reference to a web service on a remote server like such... http://10.5.1.121/PersonifyWebServicePPROD/UniversalWebService/default.wsdl The moment I invoke the web service and view its URL property it looks like... http://localhost/PersonifyWebServicePPROD/UniversalWebService/default.asmx Can anyone tell me why it's overwriting the remote server with localhost? The vendor that provided the web service said I have to reference the wsdl and not the asmx in order for it to work. I've tried running it both within IIS and as a web app on the filesystem and neither scenario work. This is on the .Net 3.5 framework.

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  • .NET ServiceInstaller get too much time for uninstall services

    - by rodnower
    Hello, we have some Setup Project wrote in Visual Studio 2008 in C# that installs and uninstalls services with ServiceInstaller class. When I install the services this don't get too much time, but when I uninstall with following code the process for each service get few seconds (and we have many services): ServiceInstaller si = new ServiceInstaler(); string path = string.Format("/assemblypath={0}", strServiceExecutablePath); string[] cmdline = { path }; InstallContext context = new InstallContext(string.Empty, cmdline); si.Context = context; si.ServiceName = strServiceName; si.Uninstall(null); Some one know why? Here I want to ask some related question. What difference between working of: InstallUtill /u exePath when it uninstall service and: sc delete serviceName And why when I delete some record from registry from CurrentControlSet\services I still see the service in services.msc but with: <Failed to read description. Error code:2 In description? From where I need to delete service manually for delete it complitely? Thank you for ahead.

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  • Calling ASP.NET web service function via GET method with jQuery

    - by the_V
    Hi, I'm trying to call web service function via GET method using jQuery, but having a problem. This is a web service code: [WebService(Namespace = "http://something.com/samples")] [ScriptService] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class TestWebService : System.Web.Services.WebService { [WebMethod] public string Test2() { string result = null; try { result = "{'result':'success', 'datetime':'" + DateTime.Now.ToString() + "'"; } catch (Exception ex) { result = "Something wrong happened"; } return result; } } That's the way I call the function: $.ajax({ type: "GET", url: "http://localhost/testwebsite/TestWebService.asmx/Test2", data: "{}", contentType: "application/json", dataType: "json", error: function (xhr, status, error) { alert(xhr.responseText); }, success: function (msg) { alert('Call was successful!'); } }); Method is called successfully, but result string gets covered by XML tags, like this: <string> {'result':'success', 'datetime':'4/26/2010 12:11:18 PM' </string> And I get an error because of this (error handler is called). Does anybody know what can be done about this?

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  • Restoring and passing data to an already running instance of a .NET application

    - by mtranda
    The goal is to have an application that runs in the system tray and can either accept user input from its actual GUI (which isn't the actual issue) OR accept command line parameters (that would actually be done via a context menu in windows explorer). Now, while I'm aware that the command line parameters are not exactly possible once the application has started, I need a way to pass data to the already running application instance via some form of handler. I'm thinking maybe define and raise some sort of event? Thanks in advance.

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  • Dynamic Data - Make Friendly Column Names?

    - by davemackey
    I've created a Dynamic Data project with an Entity Framework model. It works nicely. But, right now it shows all my database tables with the db column names - which aren't always the most friendly (e.g. address_line_1). How can I got about giving these more friendly column titles that will display to the end user?

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  • ASP.NET equivalent of this PHP code

    - by moiz217
    Please provide asp.net equivalent of this php code. $ip = $_REQUEST['ip']?$_REQUEST['ip']:$_SERVER["REMOTE_ADDR"]; $client = new SoapClient(null, array( 'location' => "http://www.itistimed.com/soap/whois-city.php", 'uri' => "http://www.itistimed.com/soap/req")); $data = $client->ipToCountryCity($ip); var_dump($data); Will display something like: array(7) { ["status"]= int(1) ["status_text"]= string(7) "Success" ["country"]= string(2) "US" ["city"]= string(13) "Mountain View" ["state"]= string(2) "CA" ["zip"]= string(5) "94043" ["org"]= string(11) "Google Inc."} thanks.

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  • Getting data from ListView control

    - by James
    I need to retrieve my data from a ListView control set up in Details mode with 5 columns. I tried using this code: MessageBox.Show(ManageList.SelectedItems(0).Text) And it works, but only for the first selected item (item 0). If I try this: MessageBox.Show(ManageList.SelectedItems(2).Text) I get this error: InvalidArgument=Value of '2' is not valid for 'index'. Parameter name: index I have no clue how I can fix this, any help? Edit: Sorry, should have said, I'm using Windows.Forms :)

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  • How LINQ to Object statements work

    - by rajbk
    This post goes into detail as to now LINQ statements work when querying a collection of objects. This topic assumes you have an understanding of how generics, delegates, implicitly typed variables, lambda expressions, object/collection initializers, extension methods and the yield statement work. I would also recommend you read my previous two posts: Using Delegates in C# Part 1 Using Delegates in C# Part 2 We will start by writing some methods to filter a collection of data. Assume we have an Employee class like so: 1: public class Employee { 2: public int ID { get; set;} 3: public string FirstName { get; set;} 4: public string LastName {get; set;} 5: public string Country { get; set; } 6: } and a collection of employees like so: 1: var employees = new List<Employee> { 2: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 3: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 4: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 5: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" }, 6: }; Filtering We wish to  find all employees that have an even ID. We could start off by writing a method that takes in a list of employees and returns a filtered list of employees with an even ID. 1: static List<Employee> GetEmployeesWithEvenID(List<Employee> employees) { 2: var filteredEmployees = new List<Employee>(); 3: foreach (Employee emp in employees) { 4: if (emp.ID % 2 == 0) { 5: filteredEmployees.Add(emp); 6: } 7: } 8: return filteredEmployees; 9: } The method can be rewritten to return an IEnumerable<Employee> using the yield return keyword. 1: static IEnumerable<Employee> GetEmployeesWithEvenID(IEnumerable<Employee> employees) { 2: foreach (Employee emp in employees) { 3: if (emp.ID % 2 == 0) { 4: yield return emp; 5: } 6: } 7: } We put these together in a console application. 1: using System; 2: using System.Collections.Generic; 3: //No System.Linq 4:  5: public class Program 6: { 7: [STAThread] 8: static void Main(string[] args) 9: { 10: var employees = new List<Employee> { 11: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 12: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 13: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 14: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" }, 15: }; 16: var filteredEmployees = GetEmployeesWithEvenID(employees); 17:  18: foreach (Employee emp in filteredEmployees) { 19: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 20: emp.ID, emp.FirstName, emp.LastName, emp.Country); 21: } 22:  23: Console.ReadLine(); 24: } 25: 26: static IEnumerable<Employee> GetEmployeesWithEvenID(IEnumerable<Employee> employees) { 27: foreach (Employee emp in employees) { 28: if (emp.ID % 2 == 0) { 29: yield return emp; 30: } 31: } 32: } 33: } 34:  35: public class Employee { 36: public int ID { get; set;} 37: public string FirstName { get; set;} 38: public string LastName {get; set;} 39: public string Country { get; set; } 40: } Output: ID 2 First_Name Jim Last_Name Ashlock Country UK ID 4 First_Name Jill Last_Name Anderson Country AUS Our filtering method is too specific. Let us change it so that it is capable of doing different types of filtering and lets give our method the name Where ;-) We will add another parameter to our Where method. This additional parameter will be a delegate with the following declaration. public delegate bool Filter(Employee emp); The idea is that the delegate parameter in our Where method will point to a method that contains the logic to do our filtering thereby freeing our Where method from any dependency. The method is shown below: 1: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 2: foreach (Employee emp in employees) { 3: if (filter(emp)) { 4: yield return emp; 5: } 6: } 7: } Making the change to our app, we create a new instance of the Filter delegate on line 14 with a target set to the method EmployeeHasEvenId. Running the code will produce the same output. 1: public delegate bool Filter(Employee emp); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: var employees = new List<Employee> { 9: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 10: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 11: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 12: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 13: }; 14: var filterDelegate = new Filter(EmployeeHasEvenId); 15: var filteredEmployees = Where(employees, filterDelegate); 16:  17: foreach (Employee emp in filteredEmployees) { 18: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 19: emp.ID, emp.FirstName, emp.LastName, emp.Country); 20: } 21: Console.ReadLine(); 22: } 23: 24: static bool EmployeeHasEvenId(Employee emp) { 25: return emp.ID % 2 == 0; 26: } 27: 28: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 29: foreach (Employee emp in employees) { 30: if (filter(emp)) { 31: yield return emp; 32: } 33: } 34: } 35: } 36:  37: public class Employee { 38: public int ID { get; set;} 39: public string FirstName { get; set;} 40: public string LastName {get; set;} 41: public string Country { get; set; } 42: } Lets use lambda expressions to inline the contents of the EmployeeHasEvenId method in place of the method. The next code snippet shows this change (see line 15).  For brevity, the Employee class declaration has been skipped. 1: public delegate bool Filter(Employee emp); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: var employees = new List<Employee> { 9: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 10: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 11: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 12: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 13: }; 14: var filterDelegate = new Filter(EmployeeHasEvenId); 15: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 16:  17: foreach (Employee emp in filteredEmployees) { 18: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 19: emp.ID, emp.FirstName, emp.LastName, emp.Country); 20: } 21: Console.ReadLine(); 22: } 23: 24: static bool EmployeeHasEvenId(Employee emp) { 25: return emp.ID % 2 == 0; 26: } 27: 28: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 29: foreach (Employee emp in employees) { 30: if (filter(emp)) { 31: yield return emp; 32: } 33: } 34: } 35: } 36:  The output displays the same two employees.  Our Where method is too restricted since it works with a collection of Employees only. Lets change it so that it works with any IEnumerable<T>. In addition, you may recall from my previous post,  that .NET 3.5 comes with a lot of predefined delegates including public delegate TResult Func<T, TResult>(T arg); We will get rid of our Filter delegate and use the one above instead. We apply these two changes to our code. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: var employees = new List<Employee> { 7: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 8: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 9: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 10: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 11: }; 12:  13: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 14:  15: foreach (Employee emp in filteredEmployees) { 16: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 17: emp.ID, emp.FirstName, emp.LastName, emp.Country); 18: } 19: Console.ReadLine(); 20: } 21: 22: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 23: foreach (var x in source) { 24: if (filter(x)) { 25: yield return x; 26: } 27: } 28: } 29: } We have successfully implemented a way to filter any IEnumerable<T> based on a  filter criteria. Projection Now lets enumerate on the items in the IEnumerable<Employee> we got from the Where method and copy them into a new IEnumerable<EmployeeFormatted>. The EmployeeFormatted class will only have a FullName and ID property. 1: public class EmployeeFormatted { 2: public int ID { get; set; } 3: public string FullName {get; set;} 4: } We could “project” our existing IEnumerable<Employee> into a new collection of IEnumerable<EmployeeFormatted> with the help of a new method. We will call this method Select ;-) 1: static IEnumerable<EmployeeFormatted> Select(IEnumerable<Employee> employees) { 2: foreach (var emp in employees) { 3: yield return new EmployeeFormatted { 4: ID = emp.ID, 5: FullName = emp.LastName + ", " + emp.FirstName 6: }; 7: } 8: } The changes are applied to our app. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: var employees = new List<Employee> { 7: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 8: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 9: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 10: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 11: }; 12:  13: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 14: var formattedEmployees = Select(filteredEmployees); 15:  16: foreach (EmployeeFormatted emp in formattedEmployees) { 17: Console.WriteLine("ID {0} Full_Name {1}", 18: emp.ID, emp.FullName); 19: } 20: Console.ReadLine(); 21: } 22:  23: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 24: foreach (var x in source) { 25: if (filter(x)) { 26: yield return x; 27: } 28: } 29: } 30: 31: static IEnumerable<EmployeeFormatted> Select(IEnumerable<Employee> employees) { 32: foreach (var emp in employees) { 33: yield return new EmployeeFormatted { 34: ID = emp.ID, 35: FullName = emp.LastName + ", " + emp.FirstName 36: }; 37: } 38: } 39: } 40:  41: public class Employee { 42: public int ID { get; set;} 43: public string FirstName { get; set;} 44: public string LastName {get; set;} 45: public string Country { get; set; } 46: } 47:  48: public class EmployeeFormatted { 49: public int ID { get; set; } 50: public string FullName {get; set;} 51: } Output: ID 2 Full_Name Ashlock, Jim ID 4 Full_Name Anderson, Jill We have successfully selected employees who have an even ID and then shaped our data with the help of the Select method so that the final result is an IEnumerable<EmployeeFormatted>.  Lets make our Select method more generic so that the user is given the freedom to shape what the output would look like. We can do this, like before, with lambda expressions. Our Select method is changed to accept a delegate as shown below. TSource will be the type of data that comes in and TResult will be the type the user chooses (shape of data) as returned from the selector delegate. 1:  2: static IEnumerable<TResult> Select<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, TResult> selector) { 3: foreach (var x in source) { 4: yield return selector(x); 5: } 6: } We see the new changes to our app. On line 15, we use lambda expression to specify the shape of the data. In this case the shape will be of type EmployeeFormatted. 1:  2: public class Program 3: { 4: [STAThread] 5: static void Main(string[] args) 6: { 7: var employees = new List<Employee> { 8: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 9: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 10: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 11: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 12: }; 13:  14: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 15: var formattedEmployees = Select(filteredEmployees, (emp) => 16: new EmployeeFormatted { 17: ID = emp.ID, 18: FullName = emp.LastName + ", " + emp.FirstName 19: }); 20:  21: foreach (EmployeeFormatted emp in formattedEmployees) { 22: Console.WriteLine("ID {0} Full_Name {1}", 23: emp.ID, emp.FullName); 24: } 25: Console.ReadLine(); 26: } 27: 28: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 29: foreach (var x in source) { 30: if (filter(x)) { 31: yield return x; 32: } 33: } 34: } 35: 36: static IEnumerable<TResult> Select<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, TResult> selector) { 37: foreach (var x in source) { 38: yield return selector(x); 39: } 40: } 41: } The code outputs the same result as before. On line 14 we filter our data and on line 15 we project our data. What if we wanted to be more expressive and concise? We could combine both line 14 and 15 into one line as shown below. Assuming you had to perform several operations like this on our collection, you would end up with some very unreadable code! 1: var formattedEmployees = Select(Where(employees, emp => emp.ID % 2 == 0), (emp) => 2: new EmployeeFormatted { 3: ID = emp.ID, 4: FullName = emp.LastName + ", " + emp.FirstName 5: }); A cleaner way to write this would be to give the appearance that the Select and Where methods were part of the IEnumerable<T>. This is exactly what extension methods give us. Extension methods have to be defined in a static class. Let us make the Select and Where extension methods on IEnumerable<T> 1: public static class MyExtensionMethods { 2: static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 3: foreach (var x in source) { 4: if (filter(x)) { 5: yield return x; 6: } 7: } 8: } 9: 10: static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 11: foreach (var x in source) { 12: yield return selector(x); 13: } 14: } 15: } The creation of the extension method makes the syntax much cleaner as shown below. We can write as many extension methods as we want and keep on chaining them using this technique. 1: var formattedEmployees = employees 2: .Where(emp => emp.ID % 2 == 0) 3: .Select (emp => new EmployeeFormatted { ID = emp.ID, FullName = emp.LastName + ", " + emp.FirstName }); Making these changes and running our code produces the same result. 1: using System; 2: using System.Collections.Generic; 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: var employees = new List<Employee> { 10: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 11: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 12: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 13: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 14: }; 15:  16: var formattedEmployees = employees 17: .Where(emp => emp.ID % 2 == 0) 18: .Select (emp => 19: new EmployeeFormatted { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: } 23: ); 24:  25: foreach (EmployeeFormatted emp in formattedEmployees) { 26: Console.WriteLine("ID {0} Full_Name {1}", 27: emp.ID, emp.FullName); 28: } 29: Console.ReadLine(); 30: } 31: } 32:  33: public static class MyExtensionMethods { 34: static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 35: foreach (var x in source) { 36: if (filter(x)) { 37: yield return x; 38: } 39: } 40: } 41: 42: static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 43: foreach (var x in source) { 44: yield return selector(x); 45: } 46: } 47: } 48:  49: public class Employee { 50: public int ID { get; set;} 51: public string FirstName { get; set;} 52: public string LastName {get; set;} 53: public string Country { get; set; } 54: } 55:  56: public class EmployeeFormatted { 57: public int ID { get; set; } 58: public string FullName {get; set;} 59: } Let’s change our code to return a collection of anonymous types and get rid of the EmployeeFormatted type. We see that the code produces the same output. 1: using System; 2: using System.Collections.Generic; 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: var employees = new List<Employee> { 10: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 11: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 12: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 13: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 14: }; 15:  16: var formattedEmployees = employees 17: .Where(emp => emp.ID % 2 == 0) 18: .Select (emp => 19: new { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: } 23: ); 24:  25: foreach (var emp in formattedEmployees) { 26: Console.WriteLine("ID {0} Full_Name {1}", 27: emp.ID, emp.FullName); 28: } 29: Console.ReadLine(); 30: } 31: } 32:  33: public static class MyExtensionMethods { 34: public static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 35: foreach (var x in source) { 36: if (filter(x)) { 37: yield return x; 38: } 39: } 40: } 41: 42: public static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 43: foreach (var x in source) { 44: yield return selector(x); 45: } 46: } 47: } 48:  49: public class Employee { 50: public int ID { get; set;} 51: public string FirstName { get; set;} 52: public string LastName {get; set;} 53: public string Country { get; set; } 54: } To be more expressive, C# allows us to write our extension method calls as a query expression. Line 16 can be rewritten a query expression like so: 1: var formattedEmployees = from emp in employees 2: where emp.ID % 2 == 0 3: select new { 4: ID = emp.ID, 5: FullName = emp.LastName + ", " + emp.FirstName 6: }; When the compiler encounters an expression like the above, it simply rewrites it as calls to our extension methods.  So far we have been using our extension methods. The System.Linq namespace contains several extension methods for objects that implement the IEnumerable<T>. You can see a listing of these methods in the Enumerable class in the System.Linq namespace. Let’s get rid of our extension methods (which I purposefully wrote to be of the same signature as the ones in the Enumerable class) and use the ones provided in the Enumerable class. Our final code is shown below: 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; //Added 4:  5: public class Program 6: { 7: [STAThread] 8: static void Main(string[] args) 9: { 10: var employees = new List<Employee> { 11: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 12: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 13: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 14: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 15: }; 16:  17: var formattedEmployees = from emp in employees 18: where emp.ID % 2 == 0 19: select new { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: }; 23:  24: foreach (var emp in formattedEmployees) { 25: Console.WriteLine("ID {0} Full_Name {1}", 26: emp.ID, emp.FullName); 27: } 28: Console.ReadLine(); 29: } 30: } 31:  32: public class Employee { 33: public int ID { get; set;} 34: public string FirstName { get; set;} 35: public string LastName {get; set;} 36: public string Country { get; set; } 37: } 38:  39: public class EmployeeFormatted { 40: public int ID { get; set; } 41: public string FullName {get; set;} 42: } This post has shown you a basic overview of LINQ to Objects work by showning you how an expression is converted to a sequence of calls to extension methods when working directly with objects. It gets more interesting when working with LINQ to SQL where an expression tree is constructed – an in memory data representation of the expression. The C# compiler compiles these expressions into code that builds an expression tree at runtime. The provider can then traverse the expression tree and generate the appropriate SQL query. You can read more about expression trees in this MSDN article.

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