How can I access an internal class from an external assembly

Question

Having an assembly which I cannot modify  vendor-supplied  which have a method returning an object type but is really of an internal type   How can I access the fields and or methods of the object from my assembly   Keep in mind that I cannot modify the vendor-supplied assembly   In essence  here s what I have   From vendor   internal class InternalClass   public string test  end class  public class Vendor   private InternalClass  internal    public object Tag  get return  internal    end class   From my assembly using the vendor assembly   public class MyClass     public void AccessTest           Vendor vendor   new Vendor        object value   vendor Tag         Here I want to access InternalClass test

User · Accepted Answer

Without access to the type  and no  InternalsVisibleTo  etc  you would have to use reflection  But a better question would be  should you be accessing this data  It isn t part of the public type contract    it sounds to me like it is intended to be treated as an opaque object  for their purposes  not yours    You ve described it as a public instance field  to get this via reflection   object obj       string value    string obj GetType   GetField  test   GetValue obj     If it is actually a property  not a field    string value    string obj GetType   GetProperty  test   GetValue obj null     If it is non-public  you ll need to use the BindingFlags overload of GetField GetProperty   Important aside  be careful with reflection like this  the implementation could change in the next version  breaking your code   or it could be obfuscated  breaking your code   or you might not have enough  trust   breaking your code   Are you spotting the pattern

User · Answer

Well  you can t  Internal classes can t be visible outside of their assembly  so no explicit way to access it directly -AFAIK of course   The only way is to use runtime late-binding via reflection  then you can invoke methods and properties from the internal class indirectly

User · Answer

Reflection   using System Reflection   Vendor vendor   new Vendor    object tag   vendor Tag   Type tagt   tag GetType    FieldInfo field   tagt GetField  test     string value   field GetValue tag     Use the power wisely   Don t forget error checking

User · Answer

I see only one case that you would allow exposure to your internal members to another assembly and that is for testing purposes   Saying that there is a way to allow  Friend  assemblies access to internals   In the AssemblyInfo cs file of the project you add a line for each assembly    assembly  InternalsVisibleTo  name of assembly here      this info is available here   Hope this helps

User · Answer

I would like to argue one point - that you cannot augment the original assembly - using Mono Cecil you can inject  InternalsVisibleTo       to the 3pty assembly  Note there might be legal implications - you re messing with 3pty assembly and technical implications - if the assembly has strong name you either need to strip it or re-sign it with different key    Install-Package Mono Cecil   And the code like   static readonly string   s toInject          alternatively  MyAssembly  PublicKey 0024000004800000    etc      MyAssembly      static void Main string   args      const string THIRD PARTY ASSEMBLY PATH     c  folder ThirdPartyAssembly dll       var parameters   new ReaderParameters       var asm   ModuleDefinition ReadModule INPUT PATH  parameters      foreach  var toInject in s toInject         var ca   new CustomAttribute         asm Import typeof InternalsVisibleToAttribute  GetConstructor new                           typeof string            ca ConstructorArguments Add new CustomAttributeArgument asm TypeSystem String  toInject         asm Assembly CustomAttributes Add ca           asm Write   c  folder-modified ThirdPartyAssembly dll          note if the assembly is strongly-signed you need to resign it like       asm Write   c  folder-modified ThirdPartyAssembly dll   new WriterParameters           StrongNameKeyPair   new StrongNameKeyPair File ReadAllBytes   c  MyKey snk

[c#] How can I access an internal class from an external assembly?

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