Assembly.LoadFile热加载DLL时第三方依赖解析问题及替代方案咨询

问题背景 #

• 目标实现DLL热加载，同事使用应用时可推送更新，无需重启即可生效
• 最初使用Assembly.LoadFrom()，但该方法倾向于加载已缓存的旧版本文件；改用Assembly.LoadFile()可加载最新版本，但需手动处理所有依赖项
• 自定义DLL的依赖问题已通过监听AppDomain.AssemblyResolve事件解决，这部分运行正常

核心问题 #

• 项目依赖Autodesk Inventor 2022的DLL，这类文件不会自动生成在Visual Studio构建目录（手动添加了部分，但仍有缺失），且本地无法找到完整依赖
• 尝试加载时抛出FileNotFoundException（非自定义异常），最先出现的是找不到Autodesk.iLogic.Core.resources.dll
• 猜测可能是当前AppDomain与Inventor共享，使用LoadFile()时需要解析Inventor自身的依赖，但无法确认原因

替代方案咨询 #

若上述第三方依赖解析问题无法解决，是否有其他策略可实现DLL不被锁定且无需关注版本号的热加载效果？

代码示例 #

Imports System.IO
Imports System.Reflection

Public NotInheritable Class LibInterface
    Private Const sBuildDir As String = "F:\Lib\Build"
    Private Const sReleaseRootDir As String = "F:\Lib\Releases"

    Private _oAssembly As System.Reflection.Assembly = Nothing
    Public Property oAssembly() As System.Reflection.Assembly
        Get
            Return _oAssembly
        End Get
        Protected Set(oVal As System.Reflection.Assembly)
            _oAssembly = oVal
        End Set
    End Property

    Private _oType As Type = Nothing
    Public Property oType() As Type
        Get
            Return _oType
        End Get
        Protected Set(oVal As Type)
            _oType = oVal
        End Set
    End Property


    Private Class Initialiser
        Public Sub New(
            ByVal oParent As LibInterface
        )
            AddHandler AppDomain.CurrentDomain.AssemblyResolve, AddressOf oParent.HandleResolve
        End Sub
    End Class

    Private _initialiser As New Initialiser(Me)

    Public Function HandleResolve(
        ByVal sender As Object _
        , ByVal args As ResolveEventArgs
    ) As System.Reflection.Assembly
        Return _GetAssembly(Split(args.Name, ",")(0) + ".dll")
    End Function


    Private Function _GetAssembly(
        ByVal sFileName As String
    ) As System.Reflection.Assembly
        Return System.Reflection.Assembly.LoadFile(_SearchLastBuild(sFileName))
    End Function

    Private Function _SearchLastBuild(
        ByVal sFileName As String
    ) As String
        Dim sPathName = System.IO.Path.Combine(sBuildDir, sFileName)
        If Not File.Exists(sPathName) Then
            Throw New FileNotFoundException(".dll not found", sPathName)
        End If
        Dim oVersionInfo As FileVersionInfo = FileVersionInfo.GetVersionInfo(sPathName)
        Dim sReleaseDir As String = System.IO.Path.Combine(sReleaseRootDir, oVersionInfo.FileVersion)
        Dim sReleasePathName = System.IO.Path.Combine(sReleaseDir, sFileName)
        If File.Exists(sReleasePathName) Then
            Return sReleasePathName
        End If
        Directory.CreateDirectory(sReleaseDir)
        _CopyFilesRecursively(sBuildDir, sReleaseDir)
        Return sReleasePathName
    End Function

    Private Sub _CopyFilesRecursively(
        ByVal sSrcPath As String _
        , ByVal sDestPath As String
    )
        For Each sDirPath As String In Directory.GetDirectories(sSrcPath, "*", SearchOption.AllDirectories)
            Directory.CreateDirectory(sDirPath.Replace(sSrcPath, sDestPath))
        Next
        For Each sOldPath As String In Directory.GetFiles(sSrcPath, "*.*", SearchOption.AllDirectories)
            File.Copy(sOldPath, sOldPath.Replace(sSrcPath, sDestPath), True)
        Next
    End Sub

    Public Sub New(
        ByVal sFileName As String _
        , ByVal sType As String
    )
        _oAssembly = _GetAssembly(sFileName)
        _oType = _oAssembly.GetType(sType, False)
    End Sub
End Class

内容的提问来源于stack exchange，提问作者davidfjdkslfs