动态加载的类上缺少属性

Question

I am using Structure Map to load plugins from a child directory.

Both the main app and the plugin reference the FileHelpers dll. FileHelpers has attributes that you put on a class to define what the record is delimited by. These are defined in my plugin. eg.

[Delimited('\t')] 
public class Test {
    public string name;
}

The FileHelpers utitlity is run from the main app using the class definitions provided by the plugins. If I put the plugin dll in a directory underneath the main application then I get an issue with the FileHelpers library complaining that the attribute cannot be found, however if it is placed next to the main library (same folder), then it works fine.

I have placed some further debug statements into my code and have found that if

var type = typeof(Test);
var attributes = type.GetCustomAttributes(true); 

is used and not the specific (the one FileHelpers is using)

var attributes = type.GetCustomAttributes(typeof(DelimitedAttribute), true);

then it finds the custom attributes without any troubles.

I thought this may have been a SM thing but have tried MEF and by doing it using Assembly.Load() and the same thing happens.

Answer 1

I think you are running into the issue described here .

According to the blog post linked in the answer , it looks like the plugin dll would need to be strongly named and fully trusted, otherwise GetCustomAttributes will filter out the DelimitedAttribute . You could try to add the AllowPartiallyTrustedCallers attribute to the plugin assembly.