小编Neh*_*eha的帖子

经过几篇文章和实例展示了其用法

AdornedElementPlaceholder

我仍然感到困惑的是,它与xaml验证结合的确切功能是什么？

我试图从.NET Core 2.0 MVC应用程序的包管理器控制台运行Add-Migration InitialCreate命令.在查看所有可能的来源之后仍然无法解决错误描述的问题:

PM> Add-Migration InitialCreate

在类'Program'上调用方法'BuildWebHost'时发生错误.继续没有应用程序服务提供商.错误:找不到方法:C:\ Users\Neha\source\repos\MvcMovie\MvcMovie\Data\MvcMovieContext.cs中的'System.Collections.Generic.Dictionary 2<System.String,System.Object> Microsoft.Extensions.Configuration.IConfigurationBuilder.get_Properties()'. System.IO.FileLoadException: Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=4.0.2.1, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) File name: 'System.Diagnostics.DiagnosticSource, Version=4.0.2.1, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' at Microsoft.EntityFrameworkCore.Infrastructure.EntityFrameworkServicesBuilder.TryAddCoreServices() at Microsoft.Extensions.DependencyInjection.SqlServerServiceCollectionExtensions.AddEntityFrameworkSqlServer(IServiceCollection serviceCollection) at Microsoft.EntityFrameworkCore.Infrastructure.Internal.SqlServerOptionsExtension.ApplyServices(IServiceCollection services) at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.ApplyServices(IDbContextOptions options, ServiceCollection services) at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>b__2(Int64 k) at System.Collections.Concurrent.ConcurrentDictionary2.GetOrAdd(TKey键,Func 2 valueFactory) at Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options) at MvcMovie.Models.MvcMovieContext..ctor(DbContextOptions1选项):第12行at MvcMovie.ToDoContextFactory.CreateDbContext(String [] args)位于C:\ Users\Neha\source\repos\MvcMovie\MvcMovie\ToDoContextFactory.cs:第17行,位于Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func 1 factory) at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType) …

根据ISO C++ 2003标准第8.3.2节

"不允许引用引用"

但我尝试在Visual C++和Ideone中使用以下代码,两个编译器都成功运行此代码.

Ideone GCC C++ 4.3.2

int main() 
{
    int i=2;
    int &ref_i=i;
    int &ref_ref_i=ref_i; // should be an error according to c++ 2003 standard

    cout<<i<<endl<<ref_i<<endl<<ref_ref_i;  
    return 0;
}

看完编译器的这种行为后我真的很困惑; 有人能解释一下吗？

在阅读c#中的属性时,我知道只有一个属性的访问者可以拥有访问修饰符,例如

私人或受保护的

例如

 public int mbox_ival
    {
        get{
            return m_ival;
        }
       protected set {

            m_ival = value;
        }

    }

现在如果我想限制两个要保护的属性,我就知道它是不允许的.在c#规范中,也就是说只有一个访问者可以拥有访问修饰符.我无法理解这背后的原因.我是c#的新手,有人可以帮忙.