[英]Assembly.LoadFrom works differently in .NET Core and .NET Framework
我有兩個.csproj
項目,它們的源代碼完全相同:
using Newtonsoft.Json.Linq;
using System;
using System.Reflection;
class Program
{
static void Main(string[] args)
{
Assembly jsonAssembly = Assembly.LoadFrom(@"C:\path\to\Newtonsoft.Json.dll");
Type reflectionType = jsonAssembly.GetType("Newtonsoft.Json.Linq.JObject");
Console.Write("Types match: " + (reflectionType == typeof(JObject)));
Console.Write("Typenames match: " + (reflectionType.FullName == typeof(JObject).FullName));
JObject cast = (JObject)Activator.CreateInstance(reflectionType);
Console.Write("Success!");
}
}
這兩個.csproj
文件對Newtonsoft.Json的引用相同:
<Reference Include="Newtonsoft.Json">
<HintPath>C:\path\to\Newtonsoft.Json.dll</HintPath>
</Reference>
這兩個項目之間的唯一區別是,我使用.NET Core 2.0創建了第一個項目,而使用.NET Framework 4.6.1創建了第二個項目。
框架:
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
<PropertyGroup>
<Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
<Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
<ProjectGuid>{A6D2C332-B60D-41F1-9983-DE10065973A1}</ProjectGuid>
<OutputType>Exe</OutputType>
<RootNamespace>ConsoleApp1</RootNamespace>
<AssemblyName>ConsoleApp1</AssemblyName>
<TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
<FileAlignment>512</FileAlignment>
<AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
<PlatformTarget>AnyCPU</PlatformTarget>
<DebugSymbols>true</DebugSymbols>
<DebugType>full</DebugType>
<Optimize>false</Optimize>
<OutputPath>bin\Debug\</OutputPath>
<DefineConstants>DEBUG;TRACE</DefineConstants>
<ErrorReport>prompt</ErrorReport>
<WarningLevel>4</WarningLevel>
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
<PlatformTarget>AnyCPU</PlatformTarget>
<DebugType>pdbonly</DebugType>
<Optimize>true</Optimize>
<OutputPath>bin\Release\</OutputPath>
<DefineConstants>TRACE</DefineConstants>
<ErrorReport>prompt</ErrorReport>
<WarningLevel>4</WarningLevel>
</PropertyGroup>
<ItemGroup>
<Reference Include="Newtonsoft.Json">
<HintPath>C:\path\to\Newtonsoft.Json.dll</HintPath>
</Reference>
<Reference Include="System" />
<Reference Include="System.Core" />
<Reference Include="System.Xml.Linq" />
<Reference Include="System.Data.DataSetExtensions" />
<Reference Include="Microsoft.CSharp" />
<Reference Include="System.Data" />
<Reference Include="System.Net.Http" />
<Reference Include="System.Xml" />
</ItemGroup>
<ItemGroup>
<Compile Include="Program.cs" />
<Compile Include="Properties\AssemblyInfo.cs" />
</ItemGroup>
<ItemGroup>
<None Include="App.config" />
</ItemGroup>
<Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
</Project>
核心:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>netcoreapp2.0</TargetFramework>
<GeneratePackageOnBuild>true</GeneratePackageOnBuild>
</PropertyGroup>
<ItemGroup>
<Reference Include="Newtonsoft.Json">
<HintPath>C:\path\to\Newtonsoft.Json.dll</HintPath>
</Reference>
</ItemGroup>
</Project>
當我使用.NET Core運行以上代碼時,得到以下響應:
Types match: True
Typenames match: True
Success!
當我使用.NET Framework運行上述代碼時,得到以下響應:
Types match: False
Typenames match: True
Unhandled Exception: System.InvalidCastException: [A]Newtonsoft.Json.Linq.JObject cannot be cast to [B]Newtonsoft.Json.Linq.JObject
為什么通過反射加載程序集時.NET Framework和.NET Core的工作原理不同?
問題可能是,在.NET Framework中,您使用2個不同的程序集(磁盤上2個不同的文件)。 嘗試以調試模式運行.NET Framework項目,並查看這些類型來自何處或添加這些行。
Console.Write("Reflection type module: " + (reflectionType.Module.FullyQualifiedName));
Console.Write("Static type module: " + (typeof(JObject).Module.FullyQualifiedName));
受沃爾特·布蘭森(Walter Branson)的回答啟發,我進行了一些研究,發現某些Load方法的行為。
/* Loads closest assembly given by FullName loaded by default, in this case it is from the same location as executable */
Assembly jsonAssembly1 = Assembly.Load(@"Newtonsoft.Json, Version=12.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed");
/* Loads assembly exaclty from the file specified by path */
Assembly jsonAssembly2 = Assembly.LoadFile($@"{pathToAssembly}\Newtonsoft.Json.dll");
/* In NET.Framework loads same assembly as LoadFrom, but in .NET Core loads same assembly as Load */
Assembly jsonAssembly3 = Assembly.LoadFrom($@"{pathToAssembly}\Newtonsoft.Json.dll");
我相信這是因為.NET的引用比較失敗。 當您查看對象時,.NET中有一個不同的句柄。 當您查看核心中的對象時,它們都有相同的句柄。
我認為這是因為您正在從文件加載程序集。 嘗試使用其完全限定的名稱加載程序集。
Assembly jsonAssembly = Assebmly.Load("NewtonSoft.Json,Version=12.0.0.0,Culture=neutral,PublicKeyToken=30adfe6b2a6aeed")
.NET Framework會將您引用的.dll復制到其可執行目錄。 因此,加載的.dll實際上是不同的。
嘗試將.NET Framework項目中的路徑從"C:\\path\\to\\Newtonsoft.Json.dll"
更改為"Newtonsoft.Json.dll"
,結果將與.NET Core中的結果相同。
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