Reflection Help with Custom Attributes

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William Wallace - 28 Jul 2005 23:41 GMT

I am unable to access the DescriptionAttribute of a method when I load the
assembly using the Assembly.ReflectionOnlyLoadFrom. After I load the assembly
I call GetTypes and loop through the types and call GetMethods. I then Loop
through the methods using CustomAttributeData.GetCustomAttributes to get the
attributes, however I can not figure out how to retrieve the
DescriptionAttribute. I had to switch back to using the regular
Assembly.LoadFrom to get it to work. I can not find any examples on how to
work with the CustomAttributeData object nor any documentation on the object
or process of using reflection to retrieve information on assemblies you have
no intention of instantiating. Can anyone help me with the process of using
reflection in the ReflectionOnly universe for retrieving Attribute info
(DescriptionAttribute specificall) ?

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William Wallace

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Mattias Sjögren - 29 Jul 2005 08:26 GMT

>I can not find any examples on how to
>work with the CustomAttributeData object nor any documentation on the object
>or process of using reflection to retrieve information on assemblies you have
>no intention of instantiating. Can anyone help me with the process of using
>reflection in the ReflectionOnly universe for retrieving Attribute info
>(DescriptionAttribute specificall) ?

Something like this

// Preload the System assembly dependency
Assembly.ReflectionOnlyLoad(typeof(DescriptionAttribute).Assembly.FullName);

// Load your assembly containing the method with the description
Assembly a = Assembly.ReflectionOnlyLoadFrom("your.dll");
MethodInfo mi = a.GetType("´TheClass").GetMethod("TheMethod");

foreach (CustomAttributeData cad in
CustomAttributeData.GetCustomAttributes(mi))
{
// Verify the attribute type is correct and that the
// parameterless constructor wasn't used.
if (cad.Constructor.DeclaringType.FullName ==
"System.ComponentModel.DescriptionAttribute" &&
cad.Constructor.GetParameters().Length > 0 &&
cad.ConstructorArguments[0].ArgumentType == typeof(string))
{
Console.WriteLine((string)cad.ConstructorArguments[0].Value);
}
}

Mattias

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Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

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William Wallace - 29 Jul 2005 09:16 GMT

thx, thats just where i got stuck :)

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William Wallace
DarkNoir@community.microsoft.com

> >I can not find any examples on how to
> >work with the CustomAttributeData object nor any documentation on the object
[quoted text clipped - 27 lines]
>
> Mattias

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Reflection Help with Custom Attributes

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