How to add folder to assembly search path at runtime in .NET?
My DLLs are loaded by a third-party application, which we can not customize. My assemblies have to be located in their own folder. I can not put them into GAC (my application has a requirement to be deployed using XCOPY). When the root DLL tries to load resource or type from another DLL (in the same folder), the loading fails (FileNotFound). Is it possible to add the folder where my DLLs are located to the assembly search path programmatically (from the root DLL)? I am not allowed to change the configuration files of the application.
Sounds like you could use the AppDomain.AssemblyResolve event and manually load the dependencies from your DLL directory.
Edit (from the comment):
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;
}
您可以将探测路径添加到应用程序的.config文件，但只有探测路径包含在您的应用程序的基本目录中时才能使用。
Update for Framework 4
Since Framework 4 raise the AssemblyResolve event also for resources actually this handler works better. It's based on the concept that localizations are in app subdirectories (one for localization with the name of the culture ie C:MyAppit for Italian) Inside there are resources file. The handler works also if the localization is country-region ie it-IT or pt-BR. In this case the handler "might be called multiple times: once for each culture in the fallback chain" [from MSDN]. This means that if we return null for "it-IT" resource file the framework raises the event asking for "it".
Event hook
AppDomain currentDomain = AppDomain.CurrentDomain;
currentDomain.AssemblyResolve += new ResolveEventHandler(currentDomain_AssemblyResolve);
Event handler
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;
}
}
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