ADO.NET :: The Constructor Of ObjectContext
Mar 8, 2011
I am confused about the constructor of ObjectContext
// Summary:
// Initializes a new instance of the System.Data.Objects.ObjectContext class
// with a given connection string and entity container name.
//
// Parameters:
// connectionString:
// The connection string, which also provides access to the metadata information.
//
// defaultContainerName:
// The name of the default entity container. When the defaultContainerName is
// set through this method, the property becomes read-only.
protected ObjectContext(string connectionString, string defaultContainerName);
I am not understanding the parameters clearly.
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Mar 3, 2011
im working with a proyect made in ASP.Net using Webforms. Im using Entity Framework to save data on Microsoft SQL.
My question is:
Is posible to use a Static class to keep the ObjectContext of EF live and put/get entities NOT saved inside the ObjectContext??
I wan to create an Object, then added with AddObject on the ObjectContext, But NOT to do the Savechanges. All this in one webform An then, in other webform, access to the ObjectContext and Get the Object added
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Oct 29, 2010
I have a page like Order - Order lines. Order represents by some textboxes and ddls, Order lines represents by GridView.
I want to let users add order lines without save changes to database. For example: he adds 4 order lines, fill order info and then hits Save button. Only an that moment all information should be saved to DB.
When I use code like
using (Entities ctx = new Entities())
{
//create new OrderLine
OrderLine ol = OrderLine.CreateOrderLine(1, 1, "", 1);
//add OrderLine to OrderLines collection
ctx.CreateOrderLines.AddObject(ol);
}
newly created OrderLine does not appears in my object context, so I can't access it and bind GridView to new OrderList collection.
How can I solve this problem? Or maybe there are another ways to perform this task?
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Apr 4, 2011
I'm building an application using MVC 3 and Entity Framework 4. I've created my Entity Data Model and generated a database from it. Now I know the validation attributes such as [Required] or [StringLength(5)] can be used on the model properties to provide validation both clientside and serverside.
I would like to know if these attributes can also be generated dynamically instead of having to add them to the model explicitly? I saw that in EF 4.1 RC you can make use of the Fluent API to further configure your model in the OnModelCreating method by using the DbModelBuilder class. As shown here I'm working with a framework however that still uses ObjectContext instead of DbContext so I would like to know if the above solution can be used in combination with ObjectContext?
As a final note, since I've been trying to figure out how to generate and use data annotations it seems using view models would increase the complexity of validation. From what I read here it seems that just passing the models directly to the view would remove the need to add annotations to the models as well as the view models. However that means that you can no longer use strongly typed views when you do joins on the models and pass those to the view directly?
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Apr 27, 2010
I'm learning EF now and have a question regarding the ObjectContext: Should I create instance of ObjectContext for every query (function) when I access the database? Or it's better to create it once (singleton) and reuse it? Before EF I was using enterprise library data access block and created instance of dataacess for DataAccess function...
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May 19, 2010
If I create a new EDMX model and then I import a function, then I can see my function generated in the Designer. If I perform the same process but I add a T4 template (for Self-Tracking Entities) then I loose the function definition, although TT file has code adding a region named "Function Imports". Is this a bug or am I performing something wrong?
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Jan 6, 2011
Here's what I want to do:
UI layer: An ASP.NET webforms website.
BLL: Business logic layer which calls the repositories on DAL.
DAL: .EDMX file (Entity Model) and ObjectContext with Repository classes which abstract the CRUD operations for each entity.
Entities: The POCO Entities. Persistence Ignorant. Generated by Microsoft's ADO.Net POCO Entity Generator.
I'd like to create an obejctcontext per HttpContext in my repositories to prevent performance/thread [un]safety issues.
public MyDBEntities ctx
{
get
{
string ocKey = "ctx_" + HttpContext.Current.GetHashCode().ToString("x");
if (!HttpContext.Current.Items.Contains(ocKey))
HttpContext.Current.Items.Add(ocKey, new MyDBEntities ());
return HttpContext.Current.Items[ocKey] as MyDBEntities ;
}
}
I don't want to access HttpContext in my DAL (Where the repositories are located). But I have to somehow pass HttpContext to DAL. based on the answer to my question here, I have to use IoC pattern.
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Feb 11, 2011
I am making multiple calls to ObjectContext.ExecuteStoreCommand with different commands and different parameters, although I use the same parameter list (object) for a several of the commands. I am getting the following exception:
System.ArgumentException: The SqlParameter is already contained by another SqlParameterCollection.
Is there a way to clear parameters between calls as I would do with straight up ADO.NET?
Updated with a code sample:
string sqlDeleteWebUserGreen = "delete WebUserGreen where WebUserId = @WebUserId";
string sqlDeleteWebUserBlue = "delete WebUserBlue where WebUserId = @WebUserId";
var argsDeleteWebUserXref = new DbParameter[] {
new SqlParameter { ParameterName = "WebUserId", Value = user.WebUserId }
rowsAffectedDeleteWebUserXref += base.context.ExecuteStoreCommand(sqlDeleteWebUserGreen, argsDeleteWebUserXref);
rowsAffectedDeleteWebUserXref += base.context.ExecuteStoreCommand(sqlDeleteWebUserBlue, argsDeleteWebUserXref);
UPDATE
Basically I am unable to find any better way of doing this, so I ended up accepting the answer below. The only difference is that I simply put the creation of the parameter into a separate method, so my calls look like base.context.ExecuteStoreCommand(sqlDeleteWebUserBlue, MethodThatWillGiveMeTheParameterArray());
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Mar 19, 2011
I have this view:
@model MatchGaming.Models.ProfileQuery
@{
ViewBag.Title = "Index";
[code]...
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May 10, 2010
What is another name of Constructor?
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Apr 6, 2010
if a class has a private constructor then it cant be instantiated. so, if i dont want my class to be instantiated and still use it, then i can make it static. what is the use of a private constructor? Also its used in singleton class, except that, is there any othe use ? (Note : The reason i am excuding the singleton case above is because I dont understand why do we need a singleton at all ? when there is a static class availble.
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Mar 30, 2011
I have a doubt concerning the Entity Framework in .NET.
I have a simple ASP .NET web page that has to insert some data in SQL Server with this function:
[code]....
The good news is that the code that Insert function encapsulates I can move it to the place which is called. So my question is: What if there is a place in which I would be forced to call the function? How then I could avoid the error. Passing the parameter as reference (I tried and did not work).
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May 25, 2010
I have a connection string defined in my web.config like:
<connectionStrings>
<add name="LibraryConnectionString" connectionString="Server=.SQLEXPRESS3;Database=Library;Integrated Security=true" />
Well...lI do not understand why when i drag-and-drop tables into a new DataClasses dbml it does not construct a default constructor specifying the connection string. I only have constructor with params like:
public DataClassesDataContext(string connection) :
base(connection, mappingSource)
{
OnCreated();
}
I do need a default constructor for LinqDataSource..
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May 14, 2010
I have the following constrcutors within a Model and I want to click the create button on a previous view and pass the projectID in and call the second Constructor so I have the projectID on this view. Do I need to change the routing in someway to call the constructor with the parameter? -
[Code]....
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Oct 29, 2010
i want to save a IQueryable in cache like this:
[Code]....
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Oct 30, 2010
I'm using Microsoft Unity. I have an interface ICustomerService and its implementation CustomerService. I can register them for the Unity container using the following code:
container.RegisterType<ICustomerService, CustomerService>(new TransientLifetimeManager());
If CustomerService has a certain parameter in its constructor (e.g. ISomeService1), I use the following code (I need to specify SomeService1):
container.RegisterType<ICustomerService, CustomerService>(new TransientLifetimeManager(), new InjectionConstructor(new SomeService1()));
No problems here. The problem appears when CustomerService class has two parameters (not one param as in the previous example) in its constructor (e.g. ISomeService1 and ISomeService2). It works fine when I'm using the following code: container.RegisterType(new TransientLifetimeManager(), new InjectionConstructor(new SomeService1(), new SomeService2()));The problem is that I do not want specify SomeService2() for the second parameter. I want to specify only first parameter - SomeService1(). But I get the error that I need to specify none or both of parameters. How can I specify only first parameter of constructor?
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Aug 7, 2010
I've created a web service , which can a method to set the user credential using Microsoft.Web.Services3.WebServicesClientProtocol. The sample code is :
<WebMethod()> _
Public Sub ClientCredential1(Of TSecurityToken As SecurityToken)_
(ByVal UserCred As Microsoft.Web.Services3.Security.Tokens.UsernameToken)
[code]....
When I run the web service it gives this error: "Microsoft.Web.Services3.Security.Tokens.UsernameToken cannot be serialized because it does not have a parameterless constructor."
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Jan 19, 2011
I have a Class called Repository for accessing (Read/Write to and from) Database.The projects that require access to the database create an object of Repository and pass the connection string as a constructor parameter for the repository to work for that particular project.
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Apr 22, 2010
I'm very new to Visual Studio and I am getting this error when trying to update an Oracle table from Gridview using a tableadapter datasource. I've followed the instructions in my text very closely but am at a loss as to why this error is occurring.
Details: System.MissingMethodException: No parameterless constructor defined for this object.
Source Error:
[Code]....
Stack Trace:
[Code]....
this is the stack trace error I am getting. At this point, I'm a little clueless how to resolve it.
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Sep 10, 2010
I am doing Music Store sample application.Here my code.
StoreViewModel
[Code]....
StoreController
[Code]....
Create.aspx
[Code]....
But when i click Save it show Error
Server Error in '/' Application.
No parameterless constructor defined for this object.
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Oct 27, 2010
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Apr 22, 2010
What's the best way to handle exceptions that happen from within a controller's constructor?
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Neither of these solutions seem ideal. Application_OnError is to broad - I have some non-mvc content in the site that has its own error handling. Using a try/catch block seems kinda hacky.
If I'm serving different content type -html/text/json/rss.... I would like to be able to handle the exception from within the action method instead of having to write all kinds of conditions to determine what kind of error message to serve.
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Jan 4, 2010
I just struck upon a prime opportunity to further exhibit my MVC ignorance, by way of the following: How can one make use of a custom view model class that has parameters in the constructor? For example, a class that could intitialize various collections/properties based on an IPrincipal object passed in. I've come across several allusions to this scenario, involving a class inheriting DefaultModelBinder which overrides the CreateModel method, but have yet to find an example.
[Code]....
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Jan 3, 2011
I receive the error "No parameterless constructor defined for this object", I have read some post on this forum about this error, but i cannot get it to work.
ViewModel
[Code]....
Controller:
[Code]....
[Code]....
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Dec 28, 2010
First I incorrectly had my node defined in /shared/web.config instead of the web.config in the root of the WebUI project. I also had not correctly defined my connection string within web.config. I have pasted the proper web.config sections below:
[code]....
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