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  • Rails - building an absolute url in a model's virtual attribute without url helper

    - by Nick
    I have a model that has paperclip attachments. The model might be used in multiple rails apps I need to return a full (non-relative) url to the attachment as part of a JSON API being consumed elsewhere. I'd like to abstract the paperclip aspect and have a simple virtual attribute like this: def thumbnail_url self.photo.url(:thumb) end This however only gives me the relative path. Since it's in the model I can't use the URL helper methods, right? What would be a good approach to prepending the application root url since I don't have helper support? I would like to avoid hardcoding something or adding code to the controller method that assembles my JSON. Thank you

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  • Beginform is not working in Asp.net mvc control whenI am trying to send the values

    - by kumar
    Hello friends i have a beginform is soemthing like this, <% using (Html.BeginForm("edit", (Model.ExceptionCategoryID == "EXP") ? "expense" : "pricing", FormMethod.Post, new { @id="exc-" + Model.ExceptionID})) { %> <input type="hidden" id="Status" runat="server"/> <%= Html.ValidationSummary(true)%> input submit button <input id="bSubmit" type="submit" class="button" value="Save" /> <script type="text/javascript"> $(document).ready(function() { $('#bSubmit').click(function() { var Status = "<%=Model.ExceptionStatus.Trim()%>"; alert(Status); $('#1_Status').attr('value',Status); }); </script> on sbmit I am trying to send the Status value.. on controler var sta = Request.Form[0]; I am getting something like 3%24Status in the From key.. why its hapeening ? thanks

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  • How to pass parameters to report model in Reporting Services

    - by savras
    I'm developing report in RS that show top N customers based on some criteria. It also allows to select number of customers and period of time. Is it possible to do it by using report model? Thing that it seems to be difficult is how to pass parameters determined by user. Another thing that in my oppinion is very disappointing is that i cannot use SQL query as dataset query, because it uses odd and elaborate XML. Although report model items seem to map its fields to query or table fields. I m concerning using report models because i need to provide uniform data model (the same tables and fields) for more or less different database schemas. It would be very nice if somebody would explain what can be done with report models and what can not.

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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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  • C# mvc 3 using selectlist with selected value in view

    - by Rob
    I'm working on a MVC3 web application. I want a list of categories shown when editing a blo from whe applications managements system. In my viewmodel i've got the following property defined for a list of selectlistitems for categories. /// <summary> /// The List of categories /// </summary> [Display(Name = "Categorie")] public IEnumerable<SelectListItem> Categories { get; set; } The next step, my controller contains the following edit action where the list of selectlistitems is filled from the database. public ActionResult Edit(Guid id) { var blogToEdit = _blogService.First(x => x.Id.Equals(id)); var listOfCategories = _categorieService.GetAll(); var selectList = listOfCategories.Select(x =>new SelectListItem{Text = x.Name, Value = x.Id.ToString(), Selected = x.Id.Equals(blogToEdit.Category.Id)}).ToList(); selectList.Insert(0, new SelectListItem{Text = Messages.SelectAnItem, Value = Messages.SelectAnItem}); var viewModel = new BlogModel { BlogId = blogToEdit.Id, Active = blogToEdit.Actief, Content = blogToEdit.Text, Title = blogToEdit.Titel, Categories = selectList //at this point i see the expected item being selected //Categories = new IEnumerable<SelectListItem>(listOfCategories, "Id", "Naam", blogToEdit.CategorieId) }; return View(viewModel); } When i set a breakpoint just before the view is being returned, i see that the selectlist is filled as i expected. So at this point everything seems to be okay. The viewmodel is filled entirely correct. Then in my view (i'm using Razor) i've got the following two rules which are supposed to render the selectlist for me. @Html.LabelFor(m => m.Categories) @Html.DropDownListFor(model=>model.Categories, Model.Categories, Model.CategoryId) @Html.ValidationMessageFor(m => m.Categories) When I run the code and open the view to edit my blog, I can see all the correct data. Also the selectlist is rendered correctly, but the item i want to be selected lost it's selection. How can this be? Until the point the viewmodel is being returned with the view everything is okay. But when i view the webpage in the browser, the selectlist is there only with out the correct selection. What am I missing here? Or doing wrong?

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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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  • dynamic model is not loading fields

    - by Toby Justus
    I am using a dynamic model found on the forum of sencha. function modelFactory(name, fields) { alert(fields); return Ext.define(name, { extend: 'Ext.data.Model', fields: fields }); } I placed the alert(fields) to check what happens with the field because it was not working. I get this: [object Object],[object Object],[object Object] How can i change this into a correct way to use it in the fields? Is there a way to check if the model has been created? With Firebug or something? EDIT: i get this in firebug: [Object { name="ccuDesignation", type=null}, Object { name="wanNumber", type=null}, Object { name="carrierName", type=null}, Object { name="dataPackageName", type=null}, Object { name="simIccid", type=null}, Object { name="expiryTime", type=null}, Object { name="bytesRx", type=null}, Object { name="bytesTx", type=null}]

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  • Retain a list of objects and pass it to the create/edit view when validation fails in ASP.NET MVC 2

    - by brainnovative
    I am binding a Foreign key property in my model. I am passing a list of possible values for that property in my model. The model looks something like this: public class UserModel { public bool Email { get; set; } public bool Name { get; set; } public RoleModel Role { get; set; } public IList<RoleModel> Roles { get; set; } } public class RoleModel { public string RoleName { get; set; } } This is what I have in the controller: public ActionResult Create() { IList<RoleModel> roles = RoleModel.FromArray(_userService.GetAllRoles()); UserModel model = new UserModel() { Roles = roles }; return View(model); } In the view I have: <div class="editor-label"> <%= Html.LabelFor(model => model.Role) %> </div> <div class="editor-field"> <%= Html.DropDownListFor(model => model.Role, new SelectList(Model.Roles, "RoleName", "RoleName", Model.Role))%> <%= Html.ValidationMessageFor(model => model.Role)%> </div> What do I need to do to get the list of roles back to my controller to pass it again to the view when validation fails. This is what I need: [HttpPost] public ActionResult Create(UserModel model) { if (ModelState.IsValid) { // insert logic here } //the validation fails so I pass the model again to the view for user to update data but model.Roles is null :( return View(model); } As written in the comments above I need to pass the model with the list of roles again to my view but model.Roles is null. Currently I ask the service again for the roles (model.Roles = RoleModel.FromArray(_userService.GetAllRoles());) but I don't want to add an extra overhead of getting the list from DB when I have already done that.. Anyone knows how to do it?

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  • Problem with altering model attributes in controller

    - by SpawnCxy
    Hi all, Today I've got a problem when I tried using following code to alter the model attribute in the controller function userlist($trigger = 1) { if($trigger == 1) { $this->User->useTable = 'betausers'; //'betausers' is completely the same structure as table 'users' } $users = $this->User->find('all'); debug($users); } And the model file is class User extends AppModel { var $name = "User"; //var $useTable = 'betausers'; function beforeFind() //only for debug { debug($this->useTable); } } The debug message in the model showed the userTable attribute had been changed to betausers.And It was supposed to show all records in table betausers.However,I still got the data in the users,which quite confused me.And I hope someone can show me some directions to solve this problem. Regards

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  • How big teams work with database

    - by Michael Riva
    Lets say I have a team, 20 developers. And we are making a project on .net. In team every one can easy create their tables according to their modules working on it. And we think to use an ORM, can you tell me how can and which ORM tools for good to working with team. Is there any proven way? I m asking becouse I never work with a team, so I dont know the best practices. So you guys what kind of pattern you use?. I realy wonder. The team members can write their unit tests and supply necessary design patterns. What kind of approach I need to create to manage team? What kind of ORM tools that we have to use?

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  • Rails Model for Playlist that can contain tracks and albums using polymorphism

    - by philk
    I struggle to find a model how to store a playlist with different type of items on it in Rails. Consider I have class Track end class Album has_many :tracks end class PlaylistItem belongs_to :playable belongs_to :playlist end class Playable belongs_to :playable, :polymorph => true end class Playlist has_many :playlist_items end I think I can use a polymorphic model "Playable" here since the Playlist can contain Tracks, Albums and maybe in the future also Movies. Also I would like to use STI for Track and Albums since they share some common attributes like title and length but also have totally different attributes. I modeled it like described here but it does not work. Anybody any idea how to model a Playlist that can contain many items of different kind?

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  • Exposing a "dumbed-down", read-only instance of a Model in GAE

    - by Blixt
    Does anyone know a clever way, in Google App Engine, to return a wrapped Model instance that only exposes a few of the original properties, and does not allow saving the instance back to the datastore? I'm not looking for ways of actually enforcing these rules, obviously it'll still be possible to change the instance by digging through its __dict__ etc. I just want a way to avoid accidental exposure/changing of data. My initial thought was to do this (I want to do this for a public version of a User model): class ReadOnlyUser(db.Model): display_name = db.StringProperty() @classmethod def kind(cls): return 'User' def put(self): raise SomeError() Unfortunately, GAE maps the kind to a class early on, so if I do ReadOnlyUser.get_by_id(1) I will actually get a User instance back, not a ReadOnlyUser instance.

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  • Can I change the datsource of report model at runtime

    - by Manab De
    I've some adhoc reports developed on some report models which are published on Report Server (we're using SSRS 2008). Everything is running well. Now in our production environment we've near about forty (40) customers who have their own database (each have the same table structures and other database objects). Now the challenge is whenever a customer will log into the report server using windows authentication and trying to view those reports we need to get the SQL data from the proper database only. Reports are designed using the report model and each model has a valid data source which is connected to particular database. We can create forty separate data sources each will be connected to specific database. My question is, is there any way through which we can change the report model data source name dynamically or during runtime based on the customer name so that during execution of the report, SSRS would fetch the data from the correct database but not from any other database. Please help me.

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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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  • How to send complete POST to Model in Code Igniter

    - by Constant M
    Hi there, What would be the best way to send a complete post to a model in Code Igniter? Methods I know are as follow: Name form elements as array, eg. <input type="text" name="contact[name]"> <input type="text" name="contact[surname]"> and then use: $this->Model_name->add_contact($this->input->post('contact')); The other would be to add each element to an array and then send it to the model as such: <input type="text" name="name"> <input type="text" name="surname"> and $contact_array = array('name' => $this->input->post('name'), 'surname' => $this->input->post('surname')); $this->Model_name->add_contact($this->input->post('contact')); Which one of these would be best practice, and is there a way to directly send a whole POST to a model (or a whole form maybe?)

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  • Deserialising Json to derived types in Asp.Net Web API

    - by IoChaos
    I'm calling a method of my WebAPI sending a json that I would like to match (or bind) with a model. In the controller I have a method like: public Result Post([ModelBinder(typeof(CustomModelBinder))]MyClass model); 'MyClass', wich is given as a parameter is an abstract class. I would like that at, depending of the type of json passed, the correct inherited class is instantiated. To achieve it, I'm trying to implement a custom binder. The problem is that (I don't know if it's very basic but I can't find anything) I don't know how to retrieve the raw Json (or better, some kind of serialization) that comes in the request. I see: actionContext.Request.Content But all methods are exposed as async. I don't know who this fits with passing the generate model to the controller method... Thanks a lot!

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  • Cant get the proper use for DropDownListFor with a model and a viewbag element

    - by EH_warch
    I have a list of locations set in the ViewBag element like this: public ActionResult Create() { var db = new ErrorReportingSystemContext(); IEnumerable<SelectListItem> items = db.Locations .AsEnumerable() .Select(c => new SelectListItem { Value =c.id.ToString(), Text = c.location_name }); ViewBag.locations = items; return View(); } I'm trying to get the values from ViewBag.locations from the view like this @Html.DropDownListFor(model => model.location_fk_id, ViewBag.locations); //@Html.DropDownListFor(model => model.location_fk_id, @ViewBag.locations); //@Html.DropDownListFor(model => model.location_fk_id, "locations"); But no avail. How can i use it?

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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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  • Query Entity Framework 4

    - by nick
    Hi, Is it possible to run a query on an EF4.0 data context and get all objects of a certain type? Say the context has books, genres & authors but I only have a generic parameter, t. Is it possible to get all of type just by using this t? I don't think it is :(

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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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  • Exam 71-515: TS: Web Applications Development with Microsoft .NET Framework 4

    - by Ricardo Peres
    I took the 71-515 exam today. 85 questions, 240 minutes. Here are some notes: Great number of jQuery questions, mostly having to do with AJAX Lots of MVC 2 questions also A number of classic ASP.NET web forms, of which only a few were related with the new 4 features Some Entity Framework Some plain old JavaScript, like, changing an image dynamically I think I did OK. As with my previous exam, I still don't know if I passed or not, will have to wait for the end of the beta period.

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  • Building vs. Buying a Master Data Management Solution

    - by david.butler(at)oracle.com
    Many organizations prefer to build their own MDM solutions. The argument is that they know their data quality issues and their data better than anyone. Plus a focused solution will cost less in the long run then a vendor supplied general purpose product. This is not unreasonable if you think of MDM as a point solution for a particular data quality problem. But this approach carries significant risk. We now know that organizations achieve significant competitive advantages when they deploy MDM as a strategic enterprise wide solution: with the most common best practice being to deploy a tactical MDM solution and grow it into a full information architecture. A build your own approach most certainly will not scale to a larger architecture unless it is done correctly with the larger solution in mind. It is possible to build a home grown point MDM solution in such a way that it will dovetail into broader MDM architectures. A very good place to start is to use the same basic technologies that Oracle uses to build its own MDM solutions. Start with the Oracle 11g database to create a flexible, extensible and open data model to hold the master data and all needed attributes. The Oracle database is the most flexible, highly available and scalable database system on the market. With its Real Application Clusters (RAC) it can even support the mixed OLTP and BI workloads that represent typical MDM data access profiles. Use Oracle Data Integration (ODI) for batch data movement between applications, MDM data stores, and the BI layer. Use Oracle Golden Gate for more real-time data movement. Use Oracle's SOA Suite for application integration with its: BPEL Process Manager to orchestrate MDM connections to business processes; Identity Management for managing users; WS Manager for managing web services; Business Intelligence Enterprise Edition for analytics; and JDeveloper for creating or extending the MDM management application. Oracle utilizes these technologies to build its MDM Hubs.  Customers who build their own MDM solution using these components will easily migrate to Oracle provided MDM solutions when the home grown solution runs out of gas. But, even with a full stack of open flexible MDM technologies, creating a robust MDM application can be a daunting task. For example, a basic MDM solution will need: a set of data access methods that support master data as a service as well as direct real time access as well as batch loads and extracts; a data migration service for initial loads and periodic updates; a metadata management capability for items such as business entity matrixed relationships and hierarchies; a source system management capability to fully cross-reference business objects and to satisfy seemingly conflicting data ownership requirements; a data quality function that can find and eliminate duplicate data while insuring correct data attribute survivorship; a set of data quality functions that can manage structured and unstructured data; a data quality interface to assist with preventing new errors from entering the system even when data entry is outside the MDM application itself; a continuing data cleansing function to keep the data up to date; an internal triggering mechanism to create and deploy change information to all connected systems; a comprehensive role based data security system to control and monitor data access, update rights, and maintain change history; a flexible business rules engine for managing master data processes such as privacy and data movement; a user interface to support casual users and data stewards; a business intelligence structure to support profiling, compliance, and business performance indicators; and an analytical foundation for directly analyzing master data. Oracle's pre-built MDM Hub solutions are full-featured 3-tier Internet applications designed to participate in the full Oracle technology stack or to run independently in other open IT SOA environments. Building MDM solutions from scratch can take years. Oracle's pre-built MDM solutions can bring quality data to the enterprise in a matter of months. But if you must build, at lease build with the world's best technology stack in a way that simplifies the eventual upgrade to Oracle MDM and to the full enterprise wide information architecture that it enables.

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