问题
I am developing a Windows UAP app in Visual Studio Ultimate CTP 2015 (latest one available in site).
I am facing issues while using await on Functions returning IAsyncActionWithProgress<>, IAsyncAction<> , IAsyncOperation<> and IAsyncOperationWithProgress<>.
I am getting the following error
Error CS0012 The type 'IAsyncActionWithProgress<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
I tried adding reference to the assembly mentioned (Windows). Even though this resolved the above error, it created another error at many other places (seems like there is a repetition of some classes/API's in both the assemblies. One of the error obtained is :
Error CS0433 The type 'Page' exists in both 'Windows.Foundation.UniversalApiContract, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime' and 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
Example of code
Windows.Storage.FileProperties.BasicProperties fileSize = await file.GetBasicPropertiesAsync();
This was working fine for a Windows Phone 8.1 app in Visual Studio 2013. What is the change I have to make to get the same result in UAP App in Visual Studio 2015.
回答1:
I had the same problem with the IAsyncAction and I have just managed to solve it, so I am going to share the (maybe not the best) solution.
First I tried repair VS, no success. Then reinstalling VS, again no success. So I went to control panel -> programs -> uninstall programs, and from there I uninstalled everything that had something to do with Visual Studio or .NET. It displayed me a couple of errors, like that some applications require this program to run, but i anyway uninstalled it (if I will need it I will install it again). After that I installed Visual Studio again, wrote the code which caused the error and, it worked, with no error.
Hope this helps you as it did help me.
回答2:
Sounds to me like your migration from Windows 8.1 to Windows 10 didn't go through quite right. Andy Wigley has a video with instructions on how to migrate a Windows 8.1 project to Windows 10. His example is for Phone but also applies to desktop. Here's the video: http://www.microsoftvirtualacademy.com/training-courses/a-developers-guide-to-windows-10-preview. Go look at the section titled "Migrating 8.1 Apps to Windows 10".
To be clear, you shouldn't need to add any references to get those types working in a Windows 10 Universal App. A good starting point (on Andy also points out in his video) is to create a new black Windows 10 Universal App project and compare your project and package manifest files to it and just bring over the changes.
回答3:
I think the issue is the following, you can deploy on the Windows Phone but when you try to access to specific functions of the Phone you need to add
回答4:
Looks like changing Project -> Properties -> Library -> Min version from any version below 14393 to 14393 or above helps with the issue.
来源：https://stackoverflow.com/questions/29671811/how-to-resolve-iasyncactionwithprogress-is-defined-in-an-assembly-that-is