C# class type - How to determine whether it is a standard .net framework class

Question

C# / .net framework

What is the most reliable way to determine whether a class (type) is a class provided by the .net framework and not any of my classes or 3rd party library classes.

I have tested some approaches

• The namespace, eg starting with "System."
• The Codebase of the assembly, where the dll is located

All this "feels" a little clumsy though it works.

Question: What is the easiest and most reliable way to determine this?

Answer 1

You could check the assembly's public key token. Microsoft (BCL) assemblies will have the public key token b77a5c561934e089 or b03f5f7f11d50a3a . WPF assemblies will have the public key token 31bf3856ad364e35 .

In general, to get the public key token of an assembly, you can use sn.exe -Tp foo.dll . sn.exe is part of the Windows SDK, which you should already have.

You can get the public key token from the assembly's full name (eg typeof(string).Assembly.FullName ), which is just a string, or you can get the raw public key token bytes from the assembly by doing a P/Invoke into StrongNameTokenFromAssembly .

Answer 2

Read the Assembly Company Attribute from the assembly [assembly: AssemblyCompany("Microsoft Corporation")]

http://msdn.microsoft.com/en-us/library/y1375e30.aspx

using System;
using System.Reflection;

[assembly: AssemblyTitle("CustAttrs1CS")]
[assembly: AssemblyDescription("GetCustomAttributes() Demo")]
[assembly: AssemblyCompany("Microsoft")]

namespace CustAttrs1CS {
    class DemoClass {
        static void Main(string[] args) {
            Type clsType = typeof(DemoClass);
            // Get the Assembly type to access its metadata.
            Assembly assy = clsType.Assembly;

            // Iterate through the attributes for the assembly.
            foreach(Attribute attr in Attribute.GetCustomAttributes(assy)) {
                // Check for the AssemblyTitle attribute.
                if (attr.GetType() == typeof(AssemblyTitleAttribute))
                    Console.WriteLine("Assembly title is \"{0}\".",
                        ((AssemblyTitleAttribute)attr).Title);

                // Check for the AssemblyDescription attribute.
                else if (attr.GetType() == 
                    typeof(AssemblyDescriptionAttribute))
                    Console.WriteLine("Assembly description is \"{0}\".",
                        ((AssemblyDescriptionAttribute)attr).Description);

                // Check for the AssemblyCompany attribute.
                else if (attr.GetType() == typeof(AssemblyCompanyAttribute))
                    Console.WriteLine("Assembly company is {0}.",
                        ((AssemblyCompanyAttribute)attr).Company);
            }
        }
    }
}

Answer 3

A couple of ideas:

In Visual Studio, within Solution Explorer, expand References, right click a reference, then choose Properties and look at the path, example:
C:\\WINDOWS\\Microsoft.NET\\Framework\\v2.0.50727\\System.dll

I'm guessing that most assemblies in C:\\WINDOWS\\Microsoft.NET\\Framework\\v2.0.50727\\ are likely to be standard .NET.

Also, you could look up the assembly in MSDN library, example:
http://msdn.microsoft.com/en-us/library/system.aspx .

Answer 4

You say about Base Class Library?

You can consult here: http://en.wikipedia.org/wiki/Base_Class_Library