.NET Tutorials, Forums, Interview Questions And Answers
Welcome :Guest
Sign In
Win Surprise Gifts!!!

Top 5 Contributors of the Month
Gaurav Pal
Post New Web Links

Count() of Navigation Property in EF

Posted By:      Posted Date: April 10, 2011    Points: 0   Category :ASP.Net


assume code as below:

public class Blog
       public int ID{get;set;}

       public virtual ICollection<Post>Posts {get;set;}

then I want to get the quantity of posts of a blog:

int c = blog.Posts.Count;


int c = blog.Posts.Count();

I find that the generated SQL shows that EF will get all posts of a blog, than calculate the Count() in memory.

if I want to let SQL caculate Count, I must write :

context.Posts.Count(p => p.Bolg == someblog)
What is right way? I like the simple code of blog.Posts.Count, but it seems with bad performance.

Thank you!

View Complete Post

More Related Resource Links

Error "Object reference not set" when I try to set a Navigation Property

I'm using Entity Framework. The following code throws a runtime error "System.NullReferenceException: Object reference not set to an instance of an object." The line before the error, it looks like newControl is in fact instantiated.My model has a Control entity and a ControlType entity. Control includes the Navigation Property "ControlType." I'm trying to set ControlType.Type = 2.SurveyFormControlsModel.Control newControl = new SurveyFormControlsModel.Control(); newControl = CreateControl(childTokenName, ControlTypeEnum.TextBox); newControl.ControlType.Type = 2; // <<--ERROR HERE context.Controls.AddObject(newControl);                                SurveyFormControlsModel.Control newControl = new SurveyFormControlsModel.Control();                                 if (listItems.Count == 0)                                 {                                     newControl = CreateControl(childTokenName, ControlTypeEnum.TextBox);                    &

How to change the value of a foreign key field/navigation property?

How can I change the value of a foreign key field?  E.g. in the Product list view instead of the value of the field Supplier.CompanyName I want to display the Supplier.Region. I searched my whole code to get a clue, googled for "change navigation property" and looked in the docs but unfortunately I did not find any hint. If you know where to find the answer, please let me know too the source of your knowledge!          

Editing a poco's navigation property without the data context



I am using EF 4.

I need to set a navigation property. I could do something like this:

using (MyDataContext context = new MyDataContext())
    affaire.QualityID = 2;

The problem is that I want to do this in the code behind and I don't have any DataContext.
The logic for using a POCO would be just doing this:
affaire.QualityID = 2;
affaire.Quality = quality;

And later let the Bll load a context, attach the poco and save the changes. But I get an error message:
"The ObjectContext instance has been disposed and can no longer be used for operations that require a connection"
Is there any way for doing this scenario?

WPF / Silverlight tutorial: Visibility property and binding

Visibility property is a very powerful and yet often overlooked property available in both WPF and Silverlight. It enables you to set Visibility of certain UIElement objects to different states like: Visible, Collapsed and Hidden (not supported by Silverlight). This tutorial shows you how to use it and how to bind to Visibility property

abstract away the source of the connection string using a class with a static property.

ASP.NET provides a configuration system we can use to keep our applications flexible at runtime. In this article we will examine some tips and best practices for using the configuration system for the best results.

The element of a web.config file is a place to store connection strings, server names, file paths, and other miscellaneous settings needed by an application to perform work. The items inside appSettings are items that need to be configurable depending upon the environment, for instance, any database connection strings will change as you move your application from a testing and staging server into production.

Let's abstract away the source of the connection string using a class with a static property.

Get pixel format, raw format, property id list and property items image in VB.net - C#.net.

n this simple article you will learn that how we can get pixel format, raw format, property id list and property items image in VB and C#.net.

Get Pixel Format:

Image consists of pixels to get the format of the pixel we have a property named pixel format. This property returns an enumeration of pixel format. This enumeration tells the pixel format.

To demonstrate make a window application. Drag one button and a picture box on form.

Now write the following code on Button click event:

Jscript error: Object does not support property or method


 Hi, i have little knowledge on javascript but i need to use this code get from somewhere for a jquery to work.

I face this "Jscript runtime error: Object does not support property or method" whenever im trying to run this page.

In my experience, im get this error msg 9 out of 10 times i use javascript in my system.

Im using Microsoft Visual web developer 2008, i wonder if this is related to my problem, i not sure there is anything i need to add as reference or update anything.

But anyway, in short, i just couldn't use javascript code when using this development tool because of this sort of error.

Anyway, it happen that last time i tried use the same type of jquery code in another project and it seems to work well without an error.

But now when im try to use it again in this recent project i created, it come out with this error and i have no idea how to solve it even look through google and this forum.

It doesn't really seems like its the code problem itself although im not sure, because any javascript code just couldn't work.

So below is my code that i need to use.

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" ></script>
<script type="text/javascript" src=&quo

Print row count on Label



I have an SP that simply performs a COUNT(*) from a table. I'm am trying to print that number in an ASP Label. It works in Query analyzer but I cant wrap my head around how to display it in a label. Any guidance much appreciated. 

Thank you. 

Is it possible to populate property choices from a database?


I'm creating my first server control, and have it working where I can set up an enum and the user can set a property's choices,  based off of that enum.  But I'd like it to pull records from a database and populate the list of choices for the property from a database.  This would allow me to add a new "Host System" to the database, and the other designers wouldn't have to get a new copy of the dll.



Custom Server Control Property not maintaining state


I have created a server control consisting of a TextArea and a div under it.  My goal is to create my own asp:TextArea type control.  the div is for a Character count of the text area and seems to work ok but i added a CharacterCountVisible property to the control that is always returning true.  See Proptery definition below


<Bindable(False), Category("Appearance"), DefaultValue("True"), Localizable(True)> Property CharacterCountVisible() As Boolean
        Return _CountBoxVisible
    End Get
    Set(ByVal value As Boolean)
        _CountBoxVisible = value
    End Set
End Property

Note the _CountBoxVisible variable is define inside the class as :

Dim _CountBoxVisible as Boolean = True

What I am trying to do is give the user/coder the option to show/utilize the char count feature.  Can make it disappear with textarea1.CharacterCountVisible = False but setting it to true will not make it display.


What am i missing





Category attribute of user control property does not work correctly in categories tab.



I have a User Control (ascx) and a property which a want to display in my categories tab in Visual Studio in the category named "Styles".

[Category("Styles"), DefaultValue(""), Description("The value for formating something.")]
public String MyFormatProperty
set { /* the code for set */; }
get { /* the code for get */; }

And here is the problem: Actually I do not need a get, because I only have to set the property (write only property). But when I omit the get, the property is displayed in the "Misc" category in the categories tab in Visual Studio. Only when I code the get as well, then the property is displayed correctly in the "Styles" category in the categories tab in Visual Studio.

Does anybody know why? How can I display the category correctly only with set?

Thanks, S.

Count words in the ascx file



I have 163 .resx files. I want to count the words in these files, because my want to translate the sentences (my task is the localisation).

Now I'm opening each file in Ms Visual Studio and I count words manually. How can I count words in all files? And the second question: can I use a program what grab strings from .resx into an editor where I can translate them and save bacn into .resx files? Or must open the files one by one and edit the text fields manually?

Thanks for helping, unfortunately I'm not a programmer.

how to increase Performance onloading page and navigation of records ?? Help








this is my aspx and cs code , let me know whether it is correct or not??

onload and performance on navigation of record show be good.

Plz help me

<CR:CrystalReportViewer ID="CrystalReportViewer1" runat="server" AutoDataBind="True"

                DisplayGroupTree="False" ReuseParameterValuesOnRefresh="true" HasToggleGroupTreeButton="False" Height="1039px" ReportSourceID="CrystalReportSource1"

                Width="901px" />

            <CR:CrystalReportSource ID="CrystalReportSource1" runat="

How to display a count of search results with keywords in a label?


Sorry for a basic post here; I am very new to VB!

I am currently building a search page, which includes a textbox and two drop-down lists, a search button, and a datagrid. If results are found and displayed, I would like a label to display:

(e.g.) "24 results found for 'blue sky clouds' "

...where the integer represents the results count, and the keywords and/or drop-down list selections are included in the string.

If no results are found I would like the label to display:

(e.g.) "No results were found that match your selection. Please try again"

I would also like the label to be invisible until a search occurs.

Thanks in advance!

Usability in Practice: Strategies for Designing Application Navigation


Good navigation makes for happy users, and happy users are good for your business. See what makes users happy this month.

Dr. Charles B. Kreitzberg and Ambrose Little

MSDN Magazine March 2009

Extreme ASP.NET: Page Navigation


In my childhood I spent several weeks a year in Holland with my extended family. As a young American boy I was fascinated with the electric Dutch trains, something we didn't see in my hometown of Dallas, Texas.

Rob Howard

MSDN Magazine October 2005

ASP.NetWindows Application  .NET Framework  C#  VB.Net  ADO.Net  
Sql Server  SharePoint  Silverlight  Others  All   

Hall of Fame    Twitter   Terms of Service    Privacy Policy    Contact Us    Archives   Tell A Friend