当 .Net 加载程序集时以及如何更改此行为？

发布于 2024-09-13 07:55:07 字数 607 浏览 3 评论 0原文

对于应用程序，我需要检查 Crystal Reports 运行时库的可用性。我尝试过的是：

    void CheckCrystal()
    {
        try
        {
            CrystalDecisions.Windows.Forms.CrystalReportViewer test = new CrystalDecisions.Windows.Forms.CrystalReportViewer();
            test.Dispose();
        }
        catch (System.Exception)
        {
            PTrace.Error("Some dependences needed to run Crystal Reports are not available.");
            throw;
        }
    }

这不起作用，因为在调用该方法之前调用 CheckCrystal 的方法中抛出了有关缺少 Crystal 依赖项的 File.IOException 。就像.Net知道它在需要它之前需要汇编一样。这是真的吗？我怎样才能改变这种行为？

提前致谢。

原文

for an application I need to check the availability of Crystal Reports runtime libraries. What I've tried is:

    void CheckCrystal()
    {
        try
        {
            CrystalDecisions.Windows.Forms.CrystalReportViewer test = new CrystalDecisions.Windows.Forms.CrystalReportViewer();
            test.Dispose();
        }
        catch (System.Exception)
        {
            PTrace.Error("Some dependences needed to run Crystal Reports are not available.");
            throw;
        }
    }

This is not working because the File.IOException about the missing Crystal dependency is thrown in the method that calls CheckCrystal before calling the method. Is like .Net knows that it will need the assembly before needing it. Is this true? How can I change this behaviour?

Thanks in advance.

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得不到的就毁灭 2024-09-20 07:55:07

这是因为代码是按方法进行 JIT 编译的，因此当您第一次尝试调用 CheckCrystal() 时，.NET 首先尝试编译它，然后加载所有必需的和尚未加载的程序集。

.NET 允许您拦截程序集解析失败的时刻。为此，请订阅 AppDomain.AssemblyResolve 事件。

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筱武穆 2024-09-20 07:55:07

您可能想要处理 AppDomain.AssemblyResolve 事件。更多信息请参见此处。

一个快速而肮脏的例子：

 AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;

 private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
 {
     if (args.Name == "CrystalReports")
     {
         PTrace.Error("Some dependences needed to run Crystal Reports are not available.");
     }

     // return located here assembly here or throw exception, etc
 }

You would probably want to handle the AppDomain.AssemblyResolve event. More information here.

A quick and dirty example:

 AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;

 private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
 {
     if (args.Name == "CrystalReports")
     {
         PTrace.Error("Some dependences needed to run Crystal Reports are not available.");
     }

     // return located here assembly here or throw exception, etc
 }

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