I have a UWP app and in one of the referenced projects the serial port is getting used. So I made that project a .NET Standard 2.0 project. The UWP app was changed to Target Windows 10 Fall Creators Update (10.0;Build 16299)
As per the compatibility chart it should have worked. But I am getting compilation error
Cannot resolve Assembly or Windows Metadata file 'Type universe cannot resolve assembly: netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51.'
I am not sure what is going wrong.
In my case it was an outdated version of the Microsoft.NETCore.UniversalWindowsPlatform nuget that was causing this problem.
Try setting not only the Target but also the Minimum version to Fall Creators Update.
When creating a UWP app in Microsoft Visual Studio, you can choose which version to target. Projects using .NET Standard 2.0 must have a Minimum Version of Build 16299 or later.
[docs]
Related
Since updating to VS2017 15.7.1 my Xamarin PCL project is showing the error below in the UWP App.xaml.cs file.
Error CS7069 Reference to type 'Assembly' claims it is defined in 'System.Runtime', but it could not be found
The offending line is copied below. IntelliSense works on the line.
Xamarin.Forms.Forms.Init(e);
There are also now a lot of conflict warning messages, for example;
Warning Found conflicts between different versions of "System.Net.Http" that could not be resolved.
The target .NET framework is 4.5, all NuGet libraries are up to date.
So far I've tried adding System.Runtime as a reference and re-installed all NuGet libraries to get rid of the error without success.
I'm still finding my way around Xamarin, any guidance to fix this would be appreciated.
Thanks,
Lefty
This happened to me recently. It was from creating an Xamarin application with PCL and changing the target from .NET standard 2.0 to .NET Standard 1.4. After downgrading the Xamarin.Forms from version 3.0.0.446417 to version 2.5.1.527436 in all the projects, it compiled without errors.
Explanation (per request):
If you are Targeting before Fall Creators Update (version 6.332), you will need to remove all references to .NET Standard 2.0.
Xamarin Forms 3.x uses .NET standard 2.0. Since you are targeting below Fall Creators Update (version 6.332) the PCL will need to be .NET Standard 1.x.
More information here.
I had the same problem with Xamarin Forms 3.0.0.446417 being installed. I just went back to the previous version, 2.5.1.527436, but then my Android project fails with "The target "CssG" does not exist in the project."
It appears to be a problem with that version of Xamarin Forms.
Goal:
From a .NET 4.7 console app, using reflection with Assembly.GetType(), I am trying extract the Type of a netstandard 2.0 class from Assembly X. Then I want to create an instance of this Type with Activator.CreateInstance().
What I am trying to do:
However, this assembly X has a dependency to netstandard 2.0. To be able to get the Type, netstandard dependency has to be loaded into the AppDomain. That's why when the AppDomain is requesting the netstandard assembly through the AssemblyResolve event, I simply load the dll like this :
var netStandardDllPath = #"C:\Users\xxx\.nuget\packages\NETStandard.Library.2.0.0-preview1-25301-01\build\netstandard2.0\ref\netstandard.dll";
return Assembly.LoadFrom(netStandardDllPath);
Which throws:
System.BadImageFormatException: 'Could not load file or assembly
'file:///C:\Users\vincent.lerouvillois.nuget\packages\NETStandard.Library.2.0.0-preview1-25301-01\build\netstandard2.0\ref\netstandard.dll'
or one of its dependencies. Reference assemblies should not be loaded
for execution. They can only be loaded in the Reflection-only loader
context. (Exception from HRESULT: 0x80131058)'
Inner Exception: BadImageFormatException: Cannot load a reference
assembly for execution.
What I know:
I know that they want us to load the DLL with Assembly.ReflectionOnlyLoadFrom. But doing that will prevent me from instanciate the type with Activator.CreateInstance(). See Microsoft official post
Also, I tried referencing the Nuget packages NETStandard.Library 2.0.0-preview1-25301-01 and NETStandard.Library.NETFramework 2.0.0-preview1-25305-02 in my console app so it would have the netstandard 2.0 libraries referenced, but it didn't change anything.
Question:
Does anyone would know if there is a proper way to load that dll without error, or maybe if this is a bug, or else? Or why this kind of dll is not able to load for execution?
The netstandard.dll you are trying to load is a reference assembly that which cannot be loaded for runtime on .NET Framework as pointed out by others. However if you need to resolve that dependency you will need to runtime version that maps to the framework you are trying to run on.
For .NET Standard support we are including them as part of the msbuild extensions that ship with VS so you will want to get the version of netstandard.dll from there. Depending on which version of VS2017 you have installed it should be somewhere like C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Microsoft\Microsoft.NET.Build.Extensions\net461\lib\netstandard.dll or from the .NET Core 2.0 SDK you can find it C:\Program Files\dotnet\sdk\2.0.0\Microsoft\Microsoft.NET.Build.Extensions\net461\lib\netstandard.dll
Try using one of those versions in your scenario.
Wow. I just spent several hours tracking the cause of this "could not load ... netstandard" error down.
For me, the problem was that my .NET Framework project (which references both .NET Framework and .NET Standard libraries) was built with .NET Framework 4.7.2 and the system where I was deploying and running it did not have 4.7.2 installed.
Deploying a very small Console project with the same basic structure and references and executing that in a Command window finally revealed the correct error, in a pop-up, that .NET Framework 4.7.2 was missing.
If you're struggling with this particular error, make sure you have the necessary .NET Framework installed.
Set Copy Local to true in netstandard.dll properties.
Open Solution Explorer and right click on netstandard.dll.
Set Copy Local to true.
You can't load a reference assembly.
.NET Standard is a collection of APIs that must be provided by .NET Standard compatible implementations.
A reference assembly only contains contracts. This means that it contains no implementation. The assembly you are trying to load contains the .NET Standard 2.0 contracts.
A contract looks like this: https://github.com/dotnet/standard/blob/master/netstandard/ref/mscorlib.cs
EDIT: .NET Framework 4.7 implements .NET Standard 2.0, so you shouldn't need to load any assembly to use Activator.CreateInstance() to instantiate a .NET Standard type.
NETStandard 2.0.0-preview1 in not compatibility with net461 and net47.
but for realese .NET Core SDK 2.0 assemblies (as well as 2.0.0-preview2)
var netStandardDllPath = #"c:\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.netcore.app\2.0.0\ref\netcoreapp2.0\netstandard.dll";
Console.WriteLine(Assembly.LoadFrom(netStandardDllPath).FullName);
all is ok.
But if you steel need to load preview1 libraries, maybe you should to use netstandard2.0 instead net471.
For me solved doing the following:
1 - Installed latest .Net Framework on server.
2 - Updated windows server and my local machine.
3 - Went to Manage Nuget Package and updated all references on the update tab.
Perhaps only doing step 3 can solve in your case
In case if IBM Message Queue references are used in the project solution, this exception indicates that the DLL used for refering MQ classes are incompatible with the host(server) .NET version installed.
In this scenario, either we need to update server with latest update and make sure .NET latest version is available or use lower version of IBM Message queue DLL as reference.
Old version DLL - amqmdnet.dll (no new features will be introduced by IBM as not in support)
Latest version DLL - amqmdnetstd.dll (to run IBM MQ classes for .NET Standard, you must install Microsoft .NET Core)
Install NetStandard.Library 2.0.0.0 from NuGet , It works for me. when I downgrade .net framework 4.6.1 to 4.6.0
If you are having this issue for a project that used to work, try deleting the bin and obj folders since caching can cause this, too.
I have a solution that contains a library and 2 applications. The applications represent the same program, with one built to target the Windows App Store through UAP10 and the other built to target a Microsoft Windows PC using .Net Framework 4.6.1. I'm using Visual Studio 2017.
I set the library project target .Net standard 1.4.
I set the UWP application to target Windows 10 Aniversary Edition (10.0; Build 14393), Min version Windows 10 (10.0; Build 10586).
I set the generic Windows application to target .Net Framework 4.6.1.
The UWP version compiles and runs fine.
Initially, the .Net Framework 4.6.1 compiles and runs. However, when I make a call to File.Open from System.IO, I get the following error message:
System.IO.FileNotFoundException: 'Could not load file or assembly
'System.IO.FileSystem, Version=4.0.1.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The
system cannot find the file specified.'
The code block with File.Run is within the library code (.Net Standard 1.4). I'm not sure what is causing the problem. I thought that I could use .Net Standard 1.4 libraries within an application that references .Net Framework 4.6.1.
As a workaround, I tried installing the Nuget package for System.IO in the .Net Framework application. System.IO Version 4.0.1.0 is not even an option. There is a version 4.0.10, but it doesn't work when this Nuget package is installed.
So, how do I properly reference System.IO operations within a .Net Framework 4.6.1 application that references the System.IO code within a .Net Standard 1.4 library?
This usually happens with "classic" csproj projects when referenced projects require overwritten override system defined types but no binding redirects are present that set this up correctly. When installing all the packages into a .net framework app (e.g. NETStandard.Library or NETStandard.Library.NETFramework(for upcoming .NET Standard 2.0)), this should be done automatically.
To force generation of binding redirects, add this to the csproj file of the .NET Framework project (if it is an executable project, the second property should be irrelevant but it doesn't hurt):
<PropertyGroup>
<AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
<GenerateBindingRedirectsOutputType>true</GenerateBindingRedirectsOutputType>
</PropertyGroup>
I have downloaded published (code behind files are no there, combined with dll in bin folder) web application from Window Server 2008 where it is hosted, and open it with Visual Studio when I debug that application it shows following error:
"Could not load assembly because this assembly is built by a runtime newer than the currently loaded runtime"
I don't know how can I solve this problem and test application locally.
Please help me.
This errors happens when the DotNet framework you are using is of older version than the one used to build the assembly. You need to check which version of framework is used to build those assemblies and then use the same or higher to debug too.
I was getting this same error when running an installer for a Windows service, even when running the installer on the PC the installer was built on.
It turned out that although the Windows service project had been updated to .NET 4.5, the Setup project that was making the installer was still set to use .NET 2.0.
To check if the Setup project is using an older version of .NET than the project to be installed, in the Visual Studio Solution Explorer:
Expand the Setup project;
Under the Setup project, expand Detected Dependencies;
Under Detected Dependencies select Microsoft .NET Framework and check the Version property. Select the appropriate .NET version from the dropdown list;
Re-build the Setup project to create a new version of the installer.
This error can have a lot of other reasons, too. I had the same problem, and nothing helped until I stumbled across this:
TlbExp.exe error:This assembly is built by a runtime newer
I just ran into this issue when the assembly was built with a target framework of .NET 4, and v4.0.30319 was installed on the server, and other 4.0 apps were running successfully.
The problem arose because the app had originally been built targeting 2.0, and new 4.0 assemblies were pushed, but not the app.config file, which we generally update separately.
This means the supportedRuntime attribute was not updated in the config and caused the error. Adding the following to the app.config fixed our issue:
<startup><supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/></startup>
One the the assemblies reference in the project might be built using a newer version of .net, check version of every assembly reference and correct accordingly.
Also check the application pool that this web site is running as. It could be framework 2.0 default on some older windows servers. Change it to framework 4.0.
I'm trying to make Npgsql, the PostgreSQL provider for .NET, available for consumption by Xamarin users. Npgsql already supports the .NET Platform Standard (version 3), and the documentation on the standard contains the following sentence:
If a library targets .NET Platform Standard version 1.3, it can only run on .NET Framework 4.6 or later, .NET Core, Universal Windows Platform 10 (UWP), and Mono/Xamarin platforms.
I can successfully install the Npgsql nuget from my Xamarin.Android project. However, when I try to build I get the following error:
System.IO.FileNotFoundException: Could not load assembly 'System.Security.Cryptography.Algorithms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Perhaps it doesn't exist in the Mono for Android profile?
Now, that packages (like many RC2 packages Npgsql depends on) has a lib/MonoAndroid10 directory containing . (also the same in ref), which seems to indicate that the package is supported on Mono.Android, but no DLL is necessary (since the logic is part of the framework). That's great, but the Xamarin.Android build process includes a ResolveAssemblies task, which walks the DLL dependency graph (this is the relevant code). Since Npgsql's netstandard13 DLL references System.Security.Cryptography.Algorthims.dll, this fails.
I'm confused that the nuget declares "it's all good", while the build process itself seems obviously incompatible with consuming netstandard13 dependencies.
Any ideas?