Type.GetType(st ring) question

[Martin Eckart]

Hi folks,

Who can explain me why the following expression does not result in getting
the correct type, but null:

Type t = Type.GetType("S ystem.Xml.XmlRe ader");

For "System.Str ing" it works as well as for "System.IO.Stre am" or
"System.Globali zation.CultureI nfo". Does that related to the constructor of
XmlReader being not public?

Thanks,
Martin

[Marc Gravell]

Type.GetType() doesn't automatically search all assemblies for the type;
actually, it expects an "assembly qualified name", but will forgive
you (i.e. allow the short name) if the type is found in either the
calling assembly (your code) or mscorlib.dll (common types).

The following is the aqn version of XmlReader (watch for wrap):

Type t = Type.GetType("S ystem.Xml.XmlRe ader, System.Xml,
Version=2.0.0.0 , Culture=neutral , PublicKeyToken= b77a5c561934e08 9");

The easiest way to get the aqn is via:
string aqn = typeof(XmlReade r).AssemblyQual ifiedName;

(then write that to the trace or something if you want it for a config
file etc)

Marc

[Martin Eckart]

Hi Marc,

That already helps.

Now, the issue I have is that I get a string value set to
"System.Xml.Xml Reader". But it could also be "System.Str ing" or
"System.Xml.Xml NodeList" or whatever. Therefore I cannot issue the code line
string aqn = typeof(XmlReade r).AssemblyQual ifiedName;
statically, but have to replace the "typeof(XmlRead er)" by something like
"typeof(<myInpu tString>)".

Is there a way to accomplish that?

Thanks,
Martin

"Marc Gravell" <ma**********@g mail.comwrote in message
news:On******** ******@TK2MSFTN GP03.phx.gbl...

Type.GetType() doesn't automatically search all assemblies for the type;
actually, it expects an "assembly qualified name", but will forgive you
(i.e. allow the short name) if the type is found in either the calling
assembly (your code) or mscorlib.dll (common types).

The following is the aqn version of XmlReader (watch for wrap):

Type t = Type.GetType("S ystem.Xml.XmlRe ader, System.Xml, Version=2.0.0.0 ,
Culture=neutral , PublicKeyToken= b77a5c561934e08 9");

The easiest way to get the aqn is via:
string aqn = typeof(XmlReade r).AssemblyQual ifiedName;

(then write that to the trace or something if you want it for a config
file etc)

Marc

[Peter Duniho]

On Tue, 20 May 2008 00:53:04 -0700, Martin Eckart <moartl17ATyaho o.de
wrote:

Who can explain me why the following expression does not result in
getting
the correct type, but null:

Type t = Type.GetType("S ystem.Xml.XmlRe ader");

Do you have the System.Xml assembly referenced in your assembly?

Pete

[Martin Eckart]

Yes, have. Has nothing do to with it.
"Peter Duniho" <Np*********@nn owslpianmk.comw rote in message
news:op******** *******@petes-computer.local. ..
On Tue, 20 May 2008 00:53:04 -0700, Martin Eckart <moartl17ATyaho o.de>
wrote:

Who can explain me why the following expression does not result in
getting
the correct type, but null:

Type t = Type.GetType("S ystem.Xml.XmlRe ader");

Do you have the System.Xml assembly referenced in your assembly?

Pete

[Jon Skeet [C# MVP]]

On May 20, 9:25 am, "Martin Eckart" <moartl17ATyaho o.dewrote:

That already helps.

Now, the issue I have is that I get a string value set to
"System.Xml.Xml Reader". But it could also be "System.Str ing" or
"System.Xml.Xml NodeList" or whatever. Therefore I cannot issue the code line
string aqn = typeof(XmlReade r).AssemblyQual ifiedName;
statically, but have to replace the "typeof(XmlRead er)" by something like
"typeof(<myInpu tString>)".

Is there a way to accomplish that?

No - typeof(...) is a compile-time operator - it looks up the type
name based on the context of the code and the referenced assemblies,
and works out the fully-qualified name at compile-time.

What you *can* do is recursively look through the assemblies
referenced by your current assembly (I can't remember the method name
off hand, but it's something obvious like
Assembly.GetRef erencedAssembli es) and call Assembly.GetTyp e on each of
those assemblies until you find the type.

Jon

[Marc Gravell]

The "typeof" line was just so you could obtain the assembly-qualified
name of the type - this isn't something you'd normally keep in the real
code. The idea being to use the assembly-qualified name *instead* of
"System.Xml.Xml Reader". Of course, if this isn't an option you'll have
to start trawling assemlbies...

Marc

[Marc Gravell]

What you *can* do is recursively look through the assemblies

referenced by your current assembly

Actually, one thing to note here is that the compiler is clever - it
will drop things that you have referenced but not used... just one to
watch if it doesn't work. You also need to watch for the circular
reference at the bottom ;-p

But something like below.

Marc

using System;
using System.Collecti ons.Generic;
using System.Reflecti on;
static class Program
{
static void Main()
{
Type type = GetType("System .Xml.XmlReader" );
}
static Type GetType(string name)
{
// tryu the lazy way first
Type type = Type.GetType(na me);
if (type != null) return type;

List<stringskip = new List<string>();
AssemblyName root = Assembly.GetEnt ryAssembly().Ge tName();
return WalkAssemblies( name, root, skip);
}
static Type WalkAssemblies( string name, AssemblyName an,
IList<stringski p)
{
// check "an" for the type
skip.Add(an.Ful lName);
Assembly a;
try {
a = Assembly.Load(a n);
} catch {
return null; // oops
}
Type type = a.GetType(name) ;
if (type != null) return type;

// see what is referenced
foreach(Assembl yName nextRef in a.GetReferenced Assemblies()) {
if(skip.Contain s(nextRef.FullN ame)) continue;
type = WalkAssemblies( name, nextRef, skip);
if (type != null) return type;
}
return null;

}
}

[Hans Kesting]

"Marc Gravell" <ma**********@g mail.comschreef in bericht
news:On******** ******@TK2MSFTN GP03.phx.gbl...

Type.GetType() doesn't automatically search all assemblies for the type;
actually, it expects an "assembly qualified name", but will forgive you
(i.e. allow the short name) if the type is found in either the calling
assembly (your code) or mscorlib.dll (common types).

The following is the aqn version of XmlReader (watch for wrap):

Type t = Type.GetType("S ystem.Xml.XmlRe ader, System.Xml, Version=2.0.0.0 ,
Culture=neutral , PublicKeyToken= b77a5c561934e08 9");

If you use just typename and assembly-name (no "Version" etc), then GetType
will find it (*if* the assembly was referenced).
So: Type t = Type.GetType("S ystem.Xml.XmlRe ader, System.Xml");

Hans Kesting