如何在.NET 运行时将文件夹添加到程序集搜索路径？

Question

我的 DLL 是由我们无法自定义的第三方应用程序加载的。我的程序集必须位于它们自己的文件夹中。我不能将它们放入 GAC（我的应用程序需要使用 XCOPY 进行部署）。 当根 DLL 尝试从另一个 DLL（在同一文件夹中）加载资源或类型时，加载失败 (FileNotFound)。 是否可以以编程方式（从根 DLL）将我的 DLL 所在的文件夹添加到程序集搜索路径中？我不允许更改应用程序的配置文件。

Answer 1

您可以将probing path 添加到应用程序的 .config 文件中，但它仅在探测路径包含在应用程序的基目录中时才有效。

Answer 2

听起来您可以使用 AppDomain.AssemblyResolve 事件并从您的 DLL 目录手动加载依赖项。

编辑（来自评论）：

AppDomain currentDomain = AppDomain.CurrentDomain;
currentDomain.AssemblyResolve += new ResolveEventHandler(LoadFromSameFolder);

static Assembly LoadFromSameFolder(object sender, ResolveEventArgs args)
{
    string folderPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
    string assemblyPath = Path.Combine(folderPath, new AssemblyName(args.Name).Name + ".dll");
    if (!File.Exists(assemblyPath)) return null;
    Assembly assembly = Assembly.LoadFrom(assemblyPath);
    return assembly;
}

Answer 3

查看 AppDomain.AppendPrivatePath（已弃用）或 AppDomainSetup.PrivateBinPath

Answer 4

最好的解释from MS itself：

AppDomain currentDomain = AppDomain.CurrentDomain;
currentDomain.AssemblyResolve += new ResolveEventHandler(MyResolveEventHandler);

private Assembly MyResolveEventHandler(object sender, ResolveEventArgs args)
{
    //This handler is called only when the common language runtime tries to bind to the assembly and fails.

    //Retrieve the list of referenced assemblies in an array of AssemblyName.
    Assembly MyAssembly, objExecutingAssembly;
    string strTempAssmbPath = "";

    objExecutingAssembly = Assembly.GetExecutingAssembly();
    AssemblyName[] arrReferencedAssmbNames = objExecutingAssembly.GetReferencedAssemblies();

    //Loop through the array of referenced assembly names.
    foreach(AssemblyName strAssmbName in arrReferencedAssmbNames)
    {
        //Check for the assembly names that have raised the "AssemblyResolve" event.
        if(strAssmbName.FullName.Substring(0, strAssmbName.FullName.IndexOf(",")) == args.Name.Substring(0, args.Name.IndexOf(",")))
        {
            //Build the path of the assembly from where it has to be loaded.                
            strTempAssmbPath = "C:\\Myassemblies\\" + args.Name.Substring(0,args.Name.IndexOf(","))+".dll";
            break;
        }

    }

    //Load the assembly from the specified path.                    
    MyAssembly = Assembly.LoadFrom(strTempAssmbPath);                   

    //Return the loaded assembly.
    return MyAssembly;          
}

Answer 5

框架 4 更新

由于 Framework 4 也为资源引发了 AssemblyResolve 事件，实际上这个处理程序工作得更好。它基于本地化位于应用程序子目录中的概念（一个用于本地化的文化名称，即 C:\MyApp\it 表示意大利语） 里面有资源文件。 如果本地化是国家/地区，即 it-IT 或 pt-BR，则处理程序也可以工作。在这种情况下，处理程序“可能会被多次调用：后备链中的每种文化一次”[来自 MSDN]。这意味着如果我们为“it-IT”资源文件返回 null，则框架会引发请求“it”的事件。

事件挂钩

        AppDomain currentDomain = AppDomain.CurrentDomain;
        currentDomain.AssemblyResolve += new ResolveEventHandler(currentDomain_AssemblyResolve);

事件处理程序

    Assembly currentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
    {
        //This handler is called only when the common language runtime tries to bind to the assembly and fails.

        Assembly executingAssembly = Assembly.GetExecutingAssembly();

        string applicationDirectory = Path.GetDirectoryName(executingAssembly.Location);

        string[] fields = args.Name.Split(',');
        string assemblyName = fields[0];
        string assemblyCulture;
        if (fields.Length < 2)
            assemblyCulture = null;
        else
            assemblyCulture = fields[2].Substring(fields[2].IndexOf('=') + 1);


        string assemblyFileName = assemblyName + ".dll";
        string assemblyPath;

        if (assemblyName.EndsWith(".resources"))
        {
            // Specific resources are located in app subdirectories
            string resourceDirectory = Path.Combine(applicationDirectory, assemblyCulture);

            assemblyPath = Path.Combine(resourceDirectory, assemblyFileName);
        }
        else
        {
            assemblyPath = Path.Combine(applicationDirectory, assemblyFileName);
        }



        if (File.Exists(assemblyPath))
        {
            //Load the assembly from the specified path.                    
            Assembly loadingAssembly = Assembly.LoadFrom(assemblyPath);

            //Return the loaded assembly.
            return loadingAssembly;
        }
        else
        {
            return null;
        }

    }

Answer 6

对于 C++/CLI 用户，这是@Mattias S 的答案（对我有用）：

using namespace System;
using namespace System::IO;
using namespace System::Reflection;

static Assembly ^LoadFromSameFolder(Object ^sender, ResolveEventArgs ^args)
{
    String ^folderPath = Path::GetDirectoryName(Assembly::GetExecutingAssembly()->Location);
    String ^assemblyPath = Path::Combine(folderPath, (gcnew AssemblyName(args->Name))->Name + ".dll");
    if (File::Exists(assemblyPath) == false) return nullptr;
    Assembly ^assembly = Assembly::LoadFrom(assemblyPath);
    return assembly;
}

// put this somewhere you know it will run (early, when the DLL gets loaded)
System::AppDomain ^currentDomain = AppDomain::CurrentDomain;
currentDomain->AssemblyResolve += gcnew ResolveEventHandler(LoadFromSameFolder);

Answer 7

我使用了@Mattias S 的解决方案。如果您确实想从同一个文件夹中解析依赖项 - 您应该尝试使用 Requesting assembly 位置，如下所示。 args.RequestingAssembly 应检查是否为空。

System.AppDomain.CurrentDomain.AssemblyResolve += (s, args) =>
{
    var loadedAssembly = System.AppDomain.CurrentDomain.GetAssemblies().Where(a => a.FullName == args.Name).FirstOrDefault();
    if(loadedAssembly != null)
    {
        return loadedAssembly;
    }

    if (args.RequestingAssembly == null) return null;

    string folderPath = Path.GetDirectoryName(args.RequestingAssembly.Location);
    string rawAssemblyPath = Path.Combine(folderPath, new System.Reflection.AssemblyName(args.Name).Name);

    string assemblyPath = rawAssemblyPath + ".dll";

    if (!File.Exists(assemblyPath))
    {
        assemblyPath = rawAssemblyPath + ".exe";
        if (!File.Exists(assemblyPath)) return null;
    } 

    var assembly = System.Reflection.Assembly.LoadFrom(assemblyPath);
    return assembly;
 };

Answer 8

我从another (marked duplicate) question 来到这里，是关于将探测标签添加到 App.Config 文件中。

我想为此添加一个旁注 - Visual Studio 已经生成了一个 App.config 文件，但是将探测标记添加到预生成的运行时标记不起作用！您需要一个单独的运行时标签，其中包含探测标签。简而言之，您的 App.Config 应该如下所示：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
    </startup>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Text.Encoding.CodePages" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.1.1.0" newVersion="4.1.1.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>

  <!-- Discover assemblies in /lib -->
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <probing privatePath="lib" />
    </assemblyBinding>
  </runtime>
</configuration>

这需要一些时间才能弄清楚，所以我将其发布在这里。也归功于The PrettyBin NuGet Package。它是一个自动移动 dll 的包。我喜欢更手动的方法，所以我没有使用它。

另外 - 这是一个将所有 .dll/.xml/.pdb 复制到 /Lib 的构建后脚本。这会整理 /debug（或 /release）文件夹，我认为这是人们试图实现的目标。

:: Moves files to a subdirectory, to unclutter the application folder
:: Note that the new subdirectory should be probed so the dlls can be found.
SET path=$(TargetDir)\lib
if not exist "%path%" mkdir "%path%"
del /S /Q "%path%"
move /Y $(TargetDir)*.dll "%path%"
move /Y $(TargetDir)*.xml "%path%"
move /Y $(TargetDir)*.pdb "%path%"