在我的案例中，ReSharper是愚蠢的，即使我的项目目标是c# 6，我也被提供了重构来使用c# 7独有的特性。

出于这个原因，我最终修改了这段代码，

private DateTime? _joinedDate;
[Column(TypeName = "DateTime2")]
public DateTime JoinedDate
{
    get { return _joinedDate ?? DateTime.Now; }
    set { _joinedDate = value; }
}

进入这段代码:

private DateTime? _joinedDate;
[Column(TypeName = "DateTime2")]
public DateTime JoinedDate
{
    get => _joinedDate ?? DateTime.Now;
    set => _joinedDate = value;
}

由于某种原因，让getter和setter使用表达式体使编译器产生元数据错误而不是语法错误。

对我来说，它发生在我将一个新项目纳入解决方案时。

Visual Studio自动选择。net framework 4.5。

像其他库一样，我将版本改为. net 4.5.2，它可以工作。

In my case it happened to me when I was referencing NuGet packages locally and moved their directory to somewhere else, I changed the path inside NuGet.Config but unfortunately I discovered that I should change the .csproject files manually to update the reference path, but the error message CS0006 was way far from describing this problem. Generally it also happens when there is a reference to DLL that couldn't be found, to be able to identify issue search your references in the project with the problem you will find some references with warning icon associated with them, try fixing those and it should work as expected.

我有这个问题，因为.nuget\NuGet.exe不包括在我的存储库。虽然我在NuGet中启用了DownloadNuGetExe。目标，它报告了一个代理错误时，试图下载它。这导致项目构建的其余部分失败。

Visual Studio 2019这对我来说很有效:

关闭Visual Studio 删除隐藏的。vs文件夹 重新打开Visual Studio并重新构建解决方案。

我发现如果你移除微软。在项目中引用CSharp程序集时，会得到这个错误。