Finding all Namespaces in an assembly using Reflection (DotNET)

Question

I've got an assembly (loaded as ReflectionOnly) and I want to find all the namespaces in this assembly so I can convert them into "using" ("Imports" in VB) statements for an auto-generated source code file template.

Ideally I'd like to restrict myself to top-level namespaces only, so instead of:

using System;
using System.Collections;
using System.Collections.Generic;

you'd only get:

using System;

I noticed there is a Namespace property on the System.Type class, but is there a better way to collect Namespaces inside an assembly that doesn't involve iterating over all types and culling duplicate namespace strings?

Much obliged, David

Answer 1

No, there's no shortcut for this, although LINQ makes it relatively easy. For example, in C# the raw "set of namespaces" would be:

var namespaces = assembly.GetTypes()
                         .Select(t => t.Namespace)
                         .Distinct();

To get the top-level namespace instead you should probably write a method:

var topLevel = assembly.GetTypes()
                       .Select(t => GetTopLevelNamespace(t))
                       .Distinct();

...

static string GetTopLevelNamespace(Type t)
{
    string ns = t.Namespace ?? "";
    int firstDot = ns.IndexOf('.');
    return firstDot == -1 ? ns : ns.Substring(0, firstDot);
}

I'm intrigued as to why you only need top level namespaces though... it seems an odd constraint.

Answer 2

Namespaces are really just a naming convention in type names, so they only "exist" as a pattern that is repeated across many qualified type names. So you have to loop through all the types. However, the code for this can probably be written as a single Linq expression.