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Entity Framework 5.0 with vs 13

There is an issue with my visual studio. When i try to generate the edmx file it does all the process very well. But as soon as i try to build the solution it throws so many errors. I am not sure if this issue is with visual studio orentity framework.
Please check the image i have attached, and the errors as well.
Here are the errors..
Error 7 A using namespace directive can only be applied to namespaces;
'System' is a type not a namespace
Error 73 The type or namespace name 'DbContext' could not be found
(are you missing a using directive or an assembly reference?)
There are so many errors.
Please help

Try to clean contents of ".vs" folder in the root of solution

SQlite implementation on Xamarin.Forms app

I have a Xamarin.Forms application and I need to be able to manage a DB. I'm developing in Microsoft Visual Studio 2017 and I'm following this tutorial dor the SQLite: https://msdn.microsoft.com/en-us/magazine/mt736454.aspx
The problem is that when I get to the point: Figure 6 Generating a Connection String in the Universal Windows Project, that is to say implementing the DatabaseConnection_UWP.cs class. There I get some errors:
using LocalDataAccess.UWP;
Here it says: The type or namespace name "LocalDataAccess" could not be found (ar you missing a using directive or an assembly reference?)
And in the line:
[assembly: Dependency(typeof(DatabaseConnection_UWP))]
It says: The type or namespace name "DatabaseConnection_UWP" could not be found (ar you missing a using directive or an assembly reference?)
The code is exactly the same, all I have done is to copy-paste from the tutorial.

Solved it following a different tutorial that worked perfectly: https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/databases/

The type or namespace name 'FacebookSessionClient' could not be found (are you missing a using directive or an assembly reference?)

I am following http://facebooksdk.net/docs/phone/tutorial/ for logging into my Windows Phone 8 app through Facebook. Upon going through the article when I try to run the application, it gives me error-
The type or namespace name 'FacebookSessionClient' could not be found (are you missing a using directive or an assembly reference?)`
and,
The type or namespace name 'FacebookSession' could not be found (are you missing a using directive or an assembly reference?)
I am sure I have added all references and namespaces. So what I am doing wrong?

I'm not really familiar with this, but have you imported everything correctly? See also https://stackoverflow.com/a/3964462/561485
For in the top of your class:
using Facebook.Session;

I think this component has been removed from the lastest version.
The way about login is replaced by
"Session.ActiveSession.LoginWithBehavior("email,public_profile,user_friends", FacebookLoginBehavior.);"
public enum FacebookLoginBehavior
{
LoginBehaviorApplicationOnly,
LoginBehaviorMobileInternetExplorerOnly,
LoginBehaviorWebViewOnly,
}
But I still try how to login by using Facebook Beta App. If you have any ideas, I think we can discuss about this issue.

This happens because of the version of the Facebook SDK and the Facebook.Client.
Above problem can be resolved by installing the Facebook SDK version 6.3.2 and the Facebook.Client version 0.40-alpha
You can download and install using the Package Manager Console and the command can be found in here and here too.

The type or namespace name 'Configuration' does not exist in the namespace 'WebApiContrib.Formatting.Html'

I'm getting this error with my Visual Studio 2012, Console App (it is a self-hosted webApi OWIN project)....
The type or namespace name 'Configuration' does not exist in the namespace
'WebApiContrib.Formatting.Html' (are you missing an assembly reference?)
The error is coming from this line ...
using WebApiContrib.Formatting.Html.Configuration;
I'm also getting a similar error for ...
using WebApiContrib.Formatting.Html.Formatters;
using WebApiContrib.Formatting.Html.Locators
In the project references I can see...
WebApiContrib.Formatting.Html
Any ideas how I can fix it please?

According to the documentation the HtmlMediaTypeViewFormatter type, and probably others, are found in WebApiContrib.Formatting.Html.Formatting. You don't need the Configuration namespace.
Check if you have installed all necessary packages and the latest version by using the NuGet package manager:
PM> Install-Package WebApiContrib.Formatting.Html

Reference to Microsoft.SharePoint.dll

I have a server that Shrepoint installed on it.
I want to test this code:
SPUtility.GetLocalizedString Method
When I add reference to Microsoft.SharePoint.dll I can resolve SPSite and ... .The problem is When I want to build the project it does not recognize using Microsoft.SharePoint any more:
and I get this error:
Error 13 The type or namespace name 'SharePoint' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
where is the problem? I add reference to Microsoft.SharePoint.dll but in build time it does not works

Microsoft.SharePoint.dll from SharePoint 2010 use Framework 3.5
but
Microsoft.SharePoint.dll from SharePoint 2013 use Framework 4.0
try it.

Change Visual Studio project solution properties platform target to x64 and the target framework to .NET Framework 3.5.

Try to use this namespace:
using Microsoft.SharePoint.Utilities
In the link you gave, it says that the method resides in Namespace Microsoft.SharePoint.Utilities instead of Microsoft.SharePoint. This is just a guess maybe work, haven't tested it,