Required Operating System: Windows Vista/7.
One of the reasons for this error to occur is due to UAC (User Account Control) and the Local Security Policy settings.
Here are the steps to fix it.
Required Operating System: Windows Vista/7.
Changing the default profile location on Windows can be quite tedious especially when you aren’t careful and messing up the default user junctions and permissions either because you accidentally deleted them or made a copy of the directory without knowing that the junctions will not be reserved; it can be quite painful to restore them manually so I’ve written a batch file to do the work.
Download: Restore Junctions
e.g. restore-user-default-junctions “D:\Users\<Some User>”
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Question: I can't see some of the files that were generated what can I do ?
Select the "Show All Files" option from the solution explorer and check whether these files were generated and add them manually.
Question: I get the following error "Value does not fall within the expected range." when I'm trying to add the generator to the model, why ?
If you already added/used the generator once in the past make sure that the following directories are deleted '\Core', '\Entities', '\Repositories' and '\T4', , Select the "Show All Files" option from the solution explorer and delete them manually.
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If anything went wrong and something is not working for you, you are more than welcome to post it at CodePlex.
Prerequisites
Creating The Database
Using The EF4 Data Generator Extension
Getting To Know The Provided Classes And Their Responsibilities
Core Classes
The following core classes are not generated by the T4 templates, they are predefined classes I wrote to extend the current functionality, so you can actually delete them if you don’t want to use them, although to do that you will need to make some changes to the T4 so it’s better to leave them.
*.Core.ObjectContextExtensions – Provides additional functionality to the ObjectContext.
*.Core.QueryableExtensions – Provides additional functionality to IQueryable.
- Page – Takes a page index and a size to perform pagination.
- SelectScalar – Takes an integer value and a property name to get a single entity.
- OrderBy – Takes a property name and direction to get a sorted results.
Entities and Repositories
The entities and the repositories are generated by the T4 templates, the names of the classes, properties and pretty much everything is taken from the entity data model (EDM).
As you can see each generated file has this suffix “*.part” as part of the name, it stands for partial, I chose to add it for two reasons.
- So I can tell tools like ReSharper to ignore these files for its analysis.
- So it will be easier to identify and distinguish the generated classes and these that are not generated.
Context, Context, Context!
The DataContextBase as pointed in the comments “Provides an access point to the data layer.” is relatively simple class which is generated by the T4 templates and allows you to access the data layer repositories.
The DataContext class is derived from the DataContextBase and allows you to alter existing functionality as well as adding functionality and is the class that you should use to get access to the repositories outside to the data layer.
By design you can’t derive from the DataContextBase outside to the data layer or derive from the DataContext at all, in my opinion like the general opinion the application shouldn’t have any persistent knowledge outside to the data layer.
The Demo Project
The demo project contains a simple example to show you how to access and work with the repositories.
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What’s T4 ?
T4 stands for Text Template Transformation Toolkit, it’s available since Visual Studio 2005 and is a template based code-generation engine.
It allows you to use a DSL and write templates that transforms into proper code that otherwise you had to write yourself.
You write the template once and you never have to do it again.
Why should we use it ?
You don’t! but it can make your work a lot easier, most of the time we write the same code over and over again and duplicate it from project to project for no reason at all.
The same repetitive code is written in every project, the only difference is that we customise it to the project requirements, we can let the the code generation handle the repetitive pieces of code and still make modifications either to the T4 itself or the generated classes.
If you may use it wisely and for the right things and purposes you may experience major improvements in code maintainability as well as productivity.
What’s the T4 Toolbox ?
The T4 Toolbox is a library developed by Oleg Sych, I use it because it helps to create a more manageable and reusable templates.
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Awhile back I’ve published my EF4.0 Data Generator and I thought like posting about the philosophy behind some of the decisions I took there and provide some more documentation to make it more useful for developers that want to use it in their work.
There are few generators that are doing almost the same thing, why another one ?
There are few reasons to that.
Abstractions and Unit Testable Repositories
Anything on the data layer that execute queries should be tested against a real database system through integration tests and integration tests only, why ?
Ask yourself why are you doing unit tests at all ? to test that the code in question is working as expected, right ?
So you mock the ObjectContext to make the repositories testable and you’re in the assumption that just because the code works and you got yourself a green bar the code will work in production ? you’re wrong.
Your mocked version just used a different kind of LINQ provider under the hood and it may not work as you expect it to work, in the worst case scenario you will have unnoticed bugs or better yet an exception, if you’re lucky.
Different LINQ providers have different functionality and features, even if everything was supported, the abstraction is mainly for testability and has no real value to the application so in my opinion it’s not worth the time and effort.
That’s exactly the reason I chose to use ObjectContext directly in my repositories.
If you want to support multiple database systems or a different kind of ORM you can just move the interfaces of the repositories into another assembly and create a dedicated assembly for each database or ORM that you want the application to support.
I’ve been really busy the past few months and I couldn’t really do anything besides work, hopefully I’ll have spare time to write and work on my blog. :)
In the upcoming months I’m going to review and write about tools I’ll start with FireFox add-ons and move on to a series of posts that focus on general computer tools, system and development.
Download Manager Tweak
Adds quite a bit of functionality and enhances the standard Download Manager that comes with FireFox.
Easy YouTube Video Downloader
Most of the videos I bother to watch in YouTube are educational videos and sometimes I feel like downloading the video and save a copy either because it’s good or is a resource that I might need in the future (can’t remember everything, you know… :)).
This tool is beyond excellent in my opinion and if you’re like me you will like it.
Googlebar Lite
Do you like your google bar ? you don’t like all its bloat and the noises it makes ? then you should definitely think about replacing it with this extension, it’s very small and quite amazing!
Status-4-Ever
Unfortunately FireFox 4.x+ doesn’t have a statusbar, it was removed and replaced with a new toy made by Mozilla called the addon bar, I don’t like it and fortunately there’s an addon that does justice to this not so useful innovation.
Tab Utilities Lite
Giving you full control over your FireFox tabs, the reason I picked it up initially was mainly due to the color customisation feature the rest is a bonus. :)
VTZilla (VirusTotal)
Did you ever wish you could perform a virus scan before downloading the file to your computer ? Well, this add-in scans your files online and with the best AV engines available.
FireFox Download Dialog.
VirusTotal Web Page.
