Question

I am trying to load dlls into my program at runtime that match a specific assembly attribute that I have set. In order to make sure that the dll is loadable before I check its flag I have written the following method:

private bool IsValidDll(string dll) {
        try {
            System.Reflection.Assembly.LoadFrom(dll);
            return true;
        } catch (Exception ex) { return false; }
    }

I can loop through dlls in my current directory and call this method to see if it will be safe to load the dll and check its assembly attributes. However, I am hitting a dll that is not throwing/catching an Exception and is still just directly crashing the program. The relevant output window information is as follows:

LoaderException: System.IO.FileLoadException: Mixed mode assembly is built against 
version 'v2.0.50727' of the runtime and cannot be loaded in the 4.0 runtime without additional configuration information. - Adapters.Spryware.SprywareAdapter
System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

I have tried catching the specific Exception (System.IO.FileLoadException) but the catch block is still skipped over and I still crash. Any thoughts?

Also, I find that this is a pretty heavy handed way of checking for my assembly attribute. Is there a way to check for my flag without having to load the dll with Reflection first?

Answer 1

Have to confess, I dont see why your code doesnt work either:

I made a .net 4 thing and ran and mine did catch it:

    private void button1_Click(object sender, EventArgs e)
    {
       // foreach (String file in Directory.GetFiles("c:\\windows", "*.dll"))
        String file = @"C:\Windows\Microsoft.NET\Framework64\v2.0.50727\System.Data.dll";
        {
            try
            {
                //System.Reflection.Assembly.ReflectionOnlyLoadFrom(file);
                System.Reflection.Assembly.LoadFrom(file);
            }
            catch (Exception ee)
            {
                textBox1.Text += ee.Message + Environment.NewLine;
            }
        }
    }

On clicking the text box reads:
Could not load file or assembly ‘file:///C:\Windows\Microsoft.NET\Framework64\v2.0.50727\System.Data.dll’ or one of its dependencies. An attempt was made to load a program with an incorrect format.