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4402

answers:

7

How to get all the classes in a namespace through reflection in C#

+1  A: 
using System.Reflection;
using System.Collections.Generic;
//...

static List<string> GetClasses(string nameSpace)
{
    Assembly asm = asm.GetExecutingAssembly();

    List<string> namespacelist = new List<string>();
    List<string> classlist = new List<string>();

    foreach (Type type in asm.GetTypes())
    {
        if (type.Namespace == nameSpace)
            namespacelist.Add(type.Name);
    }

    foreach (string classname in namespacelist)
        classlist.Add(classname);

    return classlist;
}
Ryan Farley
Note: You can do this provided you input the assembly and the NS to look for. Types can be defined in multiple assemblies and belong to the same NS.
Gishu
That is true Gishu. I suppose it would be better to pass the assembly as well as namespace from the assembly you want to remove the ambiguity.
Ryan Farley
"namespace" - reserved keyword, you should add @ prefix to make this code compile
aku
Good catch aku. Thanks, I changed the case.
Ryan Farley
I'm not trying to be mean, but there is an entirely unnecessary list and iteration through all of the found items in this code; the "classlist" variable and foreach through "namespacelist" provide no functionality different from returning "namespacelist"
TheXenocide
@TheXenocide the purpose of a code sample is not always meant to show the "best" way to write code, but to clearly convey how something is done.
Ryan Farley
I was just pointing it out for the sake of education; it's our responsibility to make the material people learn from the best example we can rather than risking a bad example that negatively influences understanding. I'm not saying this in particular is detrimental, but I disagree with the sentiment
TheXenocide
That would be great if Chethan was asking for the best practices with using Lists (which to point out, there is nothing wrong with the use of Lists in my code sample), but that could have distracted from showing him what he asked for, which was how to get classes from a namespace.
Ryan Farley
A prime example of this is aku's example using LINQ to get the results. His code is great (I loved it) but it obfuscated what Chethan was wanting to really know. Chethan is responsible for implementing this however he sees fit. Our responsibility was to show him how to get the classnames.
Ryan Farley
The problem with SO is that people will downmod an answer simply because they didn't like *how* it was answered, even though it is a completely valid and correct answer. My answer got a downmod likely because someone didn't like my use of lists, even though it is a correct answer to what was asked.
Ryan Farley
Right or wrong, voting is based on the quality of the answer, that's why every user has the right to vote. We choose our reasons for voting and the majority define which answer is regarded as the highest quality to differentiate when multiple answers are right.
TheXenocide
TheXenocide, voting has nothing to do with quality. People just vote down everything they dislike. As Ryan said we post source code not to show off *best solution ever!* but to give author some directions.
aku
so you would vote down a question just because you don't like it? What do you use to determine if you like an answer or not? Whether or not you like the author? Whether or not it uses LINQ? I try to vote on quality and applicability to the question. Opinion is subjective, but try to have some honor.
TheXenocide
I vote an answer down if it is not helpful to the question that was asked. The hint you see as you hover over the up/down vote button says "This was helpful". The decision to up/down vote an answer, for me, is whether or not it was helpful in answering the question asked.
Ryan Farley
I voted this one up because it solved a problem I was having and gave me an idea on how to solve it.
David Cumps
+1  A: 

You won't be able to get all types in a namespace, because a namespace can bridge multiple assemblies, but you can get all classes in an assembly and check to see if they belong to that namespace.

Assembly.GetTypes() works on the local assembly, or you can load an assembly first then call GetTypes() on it.

FlySwat
+4  A: 

Explained here: http://www.dreamincode.net/code/snippet1539.htm

Iterate over all classes in the assembly, and pick the ones with the correct value for their Namespace attribute.

Thomas
+18  A: 

Following code prints names of classes in specified ns defined in current assembly.
As other guys pointed, namespace can be scattered between different modules, so you need to get a list of assemblies first.

string @namespace = "...";

var q = from t in Assembly.GetExecutingAssembly().GetTypes()
        where t.IsClass && t.Namespace == @namespace
        select t;
q.ToList().ForEach(t => Console.WriteLine(t.Name));
aku
Why was this voted down?
Travis
Obfuscating your answer by needlessly using LINQ doesn't exactly help the original poster. Especially since we don't even know if he is using .NET 3.5
FlySwat
I don't know. I think it rocks.
Ryan Farley
Thanks guys, if you like, vote for it :)
aku
@Jonathan Holland, original poster can be more explicit. who knows which version of .NET he uses? Maybe he is a big fan of LINQ ?
aku
@Aku, This isn't Golf, or a "How smart are you contest", so if you purposely try to show off your knowledge, you aren't doing what this site really needs.Go put LINQ stuff in LINQ questions.
FlySwat
It seems to me like everybody wants to jump on writing the code *for* people, which I don't think benefits them as much as telling them how to do it. If somebody wants a snippet let them ask for one, if somebody wants to know how something works tell them.
TheXenocide
@TheXenocide...Exactly, are you writing code for the person, or are you writing code for yourself?Put yourself in their shoes.
FlySwat
Isn't doing something like this via a LINQ query just as valid as any other reasonable way to do it? I don't have a problem with it and I don't think it is showing off at all. I actually think it makes it nice, compact and easily readable.
Ryan Farley
@Jonathan Holland, I can assume you don't have telepathic abilities to tell that I "purposely try to show off your knowledge". If you don't like answer, vote it down. Let me decide where to put my answers, please.
aku
@TheXenocide The SO crowd can be picky depending on the mood of the day. I've answered many questions where I link to somewhere that answers the question, or give a brief "here's where to look" type answer and it gets voted down. Yet other questions get voted down because they do provide the code.
Ryan Farley
@aku, dually noted and already done :)
FlySwat
Hrm... I think it's elegant, and it's an alternative to the 'traditional' answers. I suspect that those who are against the LINQ solution are probably not using LINQ, and thus it seems unnecessary or complicated. Anyway, I like the response as an alternative implementation. Choices are always good
Travis
Trav, I think that those people, don't understand that many people are interested in answer, not only original poster. Many times I find nice solutions that were not selected as "answer" but was extremely useful for me.
aku
Also it was quite disappointed to receive such feedback from person posted http://stackoverflow.com/questions/47779/the-bury-brigade topic :)
aku
you should realize that LINQ is adding a processing layer (and an intermediate collection) with no gain for this. The difference between this and the same idea written without LINQ is the overhead of LINQ and the sacrifice of backwards compatibility (1-3.5 can be the same code). Use LINQ wisely.
TheXenocide
TheXenocide you completely misunderstand purpose of code snippets like this. I give away some code **only** to show a way how it can be implemented. It's not a "best" or "backward compatible" solution. It's one of the billions way to implement this stuff.
aku
And it is your right to do so, I only gave my rational for not considering this to be a good answer (one that I would vote up); I won't say it's a bad answer (one that I would vote down) either, but as I said to Ryan the answer that should win is the one of highest quality.
TheXenocide
Also: I don't have 3.5 on this machine so I can't say for certain, but I'm pretty sure q.ToList().ForEach can just be q.ForEach, which is an unnecessary memory block and iteration through your results further reducing the net worth of your answer.
TheXenocide
TheXenocide, ForEach is method of List class, IEnumerable doesn't have such method. If in doubt - refer to documentation
aku
So why not just use the old foreach through the results instead of wasting processing and memory converting it to a list just to foreach through it? Because it *looks* cooler? Remind me not to hire you.
TheXenocide
TheXenocide, I'm not going to discuss anything. You missed the point - code sample like this *doesn't pretend to be be BEST solution*. It's a quick sample no more no less. Just treat it as one of many possible implementations.
aku
+1  A: 

Namespaces are actually rather passive in the design of the runtime and serve primarily as organizational tools. The Full Name of a type in .NET consists of the Namespace and Class/Enum/Etc. combined. If you only wish to go through a specific assembly, you would simply loop through the types returned by assembly.GetExportedTypes() checking the value of type.Namespace. If you were trying to go through all assemblies loaded in the current AppDomain it would involve using AppDomain.CurrentDomain.GetAssemblies()

TheXenocide
+2  A: 

Here's a fix for LoaderException errors you're likely to find if one of the types sublasses a type in another assembly:

// Setup event handler to resolve assemblies
AppDomain.CurrentDomain.ReflectionOnlyAssemblyResolve += new ResolveEventHandler(CurrentDomain_ReflectionOnlyAssemblyResolve);

Assembly a = System.Reflection.Assembly.ReflectionOnlyLoadFrom(filename);
a.GetTypes();
// process types here

// method later in the class:
static Assembly CurrentDomain_ReflectionOnlyAssemblyResolve(object sender, ResolveEventArgs args)
{
    return System.Reflection.Assembly.ReflectionOnlyLoad(args.Name);
}

That should help with loading types defined in other assemblies.

Hope that helps!

Travis
+1  A: 
//a simple combined code snippet 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;

namespace MustHaveAttributes
{
  class Program
  {
    static void Main ( string[] args )
    {
      Console.WriteLine ( " START " );

      // what is in the assembly
      Assembly a = Assembly.Load ( "MustHaveAttributes" );
      Type[] types = a.GetTypes ();
      foreach (Type t in types)
      {

        Console.WriteLine ( "Type is {0}", t );
      }
      Console.WriteLine (
         "{0} types found", types.Length );

      #region Linq
      //#region Action


      //string @namespace = "MustHaveAttributes";

      //var q = from t in Assembly.GetExecutingAssembly ().GetTypes ()
      //        where t.IsClass && t.Namespace == @namespace
      //        select t;
      //q.ToList ().ForEach ( t => Console.WriteLine ( t.Name ) );


      //#endregion Action  
      #endregion

      Console.ReadLine ();
      Console.WriteLine ( " HIT A KEY TO EXIT " );
      Console.WriteLine ( " END " );
    }
  } //eof Program


  class ClassOne
  {

  } //eof class 

  class ClassTwo
  {

  } //eof class


  [System.AttributeUsage ( System.AttributeTargets.Class |
    System.AttributeTargets.Struct, AllowMultiple = true )]
  public class AttributeClass : System.Attribute
  {

    public string MustHaveDescription { get; set; }
    public string MusHaveVersion { get; set; }


    public AttributeClass ( string mustHaveDescription, string mustHaveVersion )
    {
      MustHaveDescription = mustHaveDescription;
      MusHaveVersion = mustHaveVersion;
    }

  } //eof class 

} //eof namespace
YordanGeorgiev