"ASP.global_asax does not exist in the namespace ASP"

Solution 1:

After further investigation I found that this is a known issue.

source: https://support.microsoft.com/en-us/kb/3025133

ASP.NET and Web Development

• When you create a Web Forms 4.5 WAP and open a Web Form page, you receive the following errors in the Errors List window:

• The project will run without any issues. Error CS0234 The type or namespace name 'global_asax' does not exist in the namespace 'ASP' (are you missing an assembly reference?) Error CS0234 The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference?) Assume that you use new language features for C# and VB in Visual Studio 2015 RC. You receive a runtime error when you use C# or VB in a Web Form page or in Razor Views.

To work around this issue, install Microsoft.CodeDom.Providers.DotNetCompilerPlatform NuGet package. This package will substitute the Roslyn-based provider for the in-box CodeDom providers for ASP.NET.

Solution 2:

I had the same issue.

I manually edited the generated file file.cshtml.72cecc2a.cs (it was at AppData\Local\Temp\Temporary ASP.NET Files\root) and changed ASP.global_asax to System.Web.HttpApplication and the error went away.

This is the generated code:

protected static ASP.global_asax ApplicationInstance {
    get {
        return ((ASP.global_asax)(Context.ApplicationInstance));
    }
}

I changed it to:

protected static System.Web.HttpApplication ApplicationInstance {
    get {
        return ((System.Web.HttpApplication)(Context.ApplicationInstance));
    }
}

I don't know why this is happening though.

Solution 3:

I've found that if I have the files in App_Code open in Visual Studio 2015 when I run the build, then I don't get the errors. As soon as I close the files the errors show up again.

Solution 4:

After trying a variety of the solutions proposed here, it turns out that simply quitting Visual Studio 2015 and then restarting it was enough to get the Solution/Project to successfully compile once again.

Solution 5:

Two things i did to resolve this was to re-target the framework and then changing it back (was using 4.5.1 changed it to 4.5 and back)

After this i had a lot of error with T4MVC which i was also using, i upgraded it to newest version but i could see that in source control that T4MVC was installed targeting framework 4.5 and when you re/install a new nuget package it changes the target framework, so that was changed to 4.5.1

After this everything worked. I didn't test if you only need to do that second part of this answer, but i would try that first.