//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 

在一行中通过Namespace名称的一部分获取所有类:

var allClasses = Assembly.GetExecutingAssembly().GetTypes().Where(a => a.IsClass && a.Namespace != null && a.Namespace.Contains(@"..your namespace...")).ToList();

正如FlySwat所说，您可以在多个程序集中拥有相同的命名空间(例如System.Collections.Generic)。如果还没有加载所有这些程序集，则必须加载它们。完整的答案是:

AppDomain.CurrentDomain.GetAssemblies()
                       .SelectMany(t => t.GetTypes())
                       .Where(t => t.IsClass && t.Namespace == @namespace)

这应该工作，除非你想要其他域的类。要获得所有域名的列表，请点击此链接。

using System.Reflection;
using System.Collections.Generic;
//...

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

注:上面的代码说明了发生了什么。如果你要实现它，可以使用一个简化版本:

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

static IEnumerable<string> GetClasses(string nameSpace)
{
    Assembly asm = Assembly.GetExecutingAssembly();
    return asm.GetTypes()
        .Where(type => type.Namespace == nameSpace)
        .Select(type => type.Name);
}

以下代码打印当前程序集中定义的指定名称空间中的类名称。 正如其他人指出的那样，名称空间可以分散在不同的模块之间，因此需要首先获得程序集列表。

string nspace = "...";

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

对于特定的程序集，命名空间和ClassName:

var assemblyName = "Some.Assembly.Name"
var nameSpace = "Some.Namespace.Name";
var className = "ClassNameFilter";

var asm = Assembly.Load(assemblyName);
var classes = asm.GetTypes().Where(p =>
     p.Namespace == nameSpace &&
     p.Name.Contains(className) 
).ToList();

注意:项目必须引用程序集