xamarin - 更新到 Visual Studio 2017 版本 15.8 预览版后，出现 "Can not resolve reference: ` System.Memory `"或 "Could not find ` System.Memory `"

Question

如果它可能对其他人有帮助，我将询问并回答这个关于从 Visual Studio 2017 版本 15.7 更新到版本 15.8 预览版后 Xamarin.Android 和 Xamarin.iOS 项目中可能出现的问题的小问题。

演示该问题的示例步骤

1. 创建一个新的空白 Xamarin.Android 或 Xamarin.iOS 项目。
2. 将 Microsoft.AspNetCore.SignalR.Client.Core 版本 1.0.0 NuGet 包添加到项目中。

3. 使用项目中 NuGet 包中的类型。例如，将以下行添加到任何现有方法中:

   var connection = new Microsoft.AspNetCore.SignalR.Client.HubConnectionBuilder().Build();
   

4. 对于 Xamarin.Android，尝试在调试配置中构建项目。对于 Xamarin.iOS，在 iPhone 模拟器上的调试配置中构建并运行应用程序。

Visual Studio 2017 版本 15.7 的结果

Xamarin.Android 应用和 Xamarin.iOS 应用均构建并运行，没有错误。

Visual Studio 2017 版本 15.8 预览版 4 的结果

对于 Xamarin.Android，构建失败:

Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `Microsoft.AspNetCore.Connections.Abstractions`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `Microsoft.AspNetCore.Connections.Abstractions`.
Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `Microsoft.AspNetCore.SignalR.Client.Core`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `Microsoft.AspNetCore.SignalR.Client.Core`.
Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `Microsoft.AspNetCore.SignalR.Common`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `Microsoft.AspNetCore.SignalR.Common`.
Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `Microsoft.AspNetCore.SignalR.Protocols.Json`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `Microsoft.AspNetCore.SignalR.Protocols.Json`.
Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `Microsoft.Extensions.Primitives`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `Microsoft.Extensions.Primitives`.
Xamarin.Android.Common.targets(1831,2): error XA2002: Can not resolve reference: `System.Memory`, referenced by `System.IO.Pipelines`. Please add a NuGet package or assembly reference for `System.Memory`, or remove the reference to `System.IO.Pipelines`.

对于 Xamarin.iOS，应用程序在模拟器上成功启动，但调试输出显示应用程序在运行时无法找到 System.Memory:

Could not find `System.Memory` referenced by assembly `System.IO.Pipelines, Version=4.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51`.
Could not find `System.Memory` referenced by assembly `Microsoft.AspNetCore.SignalR.Client.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60`.
Could not find `System.Memory` referenced by assembly `Microsoft.AspNetCore.SignalR.Common, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60`.
Could not find `System.Memory` referenced by assembly `Microsoft.Extensions.Primitives, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60`.
Could not find `System.Memory` referenced by assembly `Microsoft.AspNetCore.Connections.Abstractions, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60`.
Could not find `System.Memory` referenced by assembly `Microsoft.AspNetCore.SignalR.Protocols.Json, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60`.

如何解决这些错误？后续，为什么我更新Visual Studio后会出现这些错误？

Answer 1

我使用 VS Entreprise 2017 版本 15.9.1

要解决我面临的问题(无法解析引用:System.Buffers，由System.Memory引用。请为添加NuGet包或程序集引用>System.Buffers，或删除对 System.Memory 的引用。)， 我只是通过以下命令安装 System.Buffers 包:

安装包 System.Buffers -版本 4.5.0

https://www.nuget.org/packages/System.Buffers/