Channel 9 - Discussions by jrg

Tech Off - Set IIsWebDirectory Permissions via WMI in C#

jrg — Sat, 12 Mar 2005 15:32:09 GMT

mrichman wrote:

Yet another setback I discovered is that to create a Metabase entry for /foo/bar, its parent key /foo must exist.

Looks like I need to create a recursive method for creating a key if and only if its parent exists (creating the parent key if not there).

Kill me now please.

Copyright your problem and solution before it becomes the next Microsoft interview question!

"Umm, let me think, string path = "some/path"; string [] pathParts = path.Split('/'); recursiveFunction(rootPath, pathParts, 0)..."

Tech Off - Set IIsWebDirectory Permissions via WMI in C#

jrg — Thu, 10 Mar 2005 21:26:05 GMT

I'm doing a compare and contrast with your code and some Microsoft example code in VBScript:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/iissdk/html/504d8e75-4a12-433b-8894-ac7fd414a634.asp

I know the following is using IIsWebVirtualDirectory rather than IIsWebDirectory but the concept should still be valid:

_{const APP_POOLED = 2 
var strNewVdir 
strNewVdir = "W3SVC/1/Root/newVdir" 
 
' Make connections to WMI, to the IIS namespace on MyMachine. 
set locatorObj = CreateObject("WbemScripting.SWbemLocator") 
set providerObj = locatorObj.ConnectServer("MyMachine", "root/MicrosoftIISv2") 
 
' Add a virtual directory to the site. This requires SpawnInstance(). 
Set vdirClassObj = providerObj.Get("IIsWebVirtualDirSetting") 
Set vdirObj = vdirClassObj.SpawnInstance_() 
vdirObj.Name = strNewVdir 
vdirObj.Path = "C:\Inetpub\Wwwroot" 
vdirObj.AuthFlags = 5 ' AuthNTLM + AuthAnonymous 
vdirObj.EnableDefaultDoc = True 
vdirObj.DirBrowseFlags = &H4000003E ' date, time, size, extension, longdate 
vdirObj.AccessFlags = 513 ' read, script 
 
' Save the new settings to the metabase 
vdirObj.Put_() 
 
' Create a pooled application on the new virtual directory. 
Set vdirObj = providerObj.Get("IIsWebVirtualDir='" & strNewVdir & "'") 
vdirObj.AppCreate2(2) 
 
' Set the application name. 
Set vdirObj = providerObj.Get("IIsWebVirtualDirSetting='" & strNewVdir & "'") 
vdirObj.AppFriendlyName = "Root Application" 
vdirObj.Put_()}

"SpawnInstance()" sticks out as something to research as they say it is "required" which tells me it can be a sticky point. It appears that they create the object without yet giving the path... just create an IIsWebDirectorySetting object first, no path. Next, on your object, set the properties. I'm not set up to test this so forgive me if this is getting off base. Once you've set your properties, including a path and name, then you may find it does the Put properly.

Tech Off - T == null => Boxing = Problem

jrg — Thu, 10 Mar 2005 20:35:59 GMT

Here's a fun one I ran into yesterday... not exactly part of this thread but I don't think it's justified to start a new thread:

Given an abstract class, create a field that is readonly which can be set by inheriting classes.

const fields are compiler time only.
readonly fields are allowed to be set at runtime in the constructor or as a field initialization. This definition is a little gray in addressing "what about inheriting types and their constructors?"

The answer is that readonly cannot be set by the inheriting class.

Here's one way to get that functionality though:

public abstract class A
{
   protected readonly int myField;
   protected A(int myField)
   {
      this.myField = myField;
   }
}

public class B:A
{
   public B(): base(4) // valid
   {
   // base.myField = 4; // invalid
   }
}

Tech Off - T == null => Boxing = Problem

jrg — Thu, 10 Mar 2005 20:27:56 GMT

Yep... it's a pretty cool exercise though... you never know what you don't know until it presents itself and you work it out.

Tech Off - T == null => Boxing = Problem

jrg — Thu, 10 Mar 2005 20:25:34 GMT

I think in a way it's the same yet an inverse, if that makes any sense. An analogy would be that Object is the universal template for all types. The problem though is when an implicit cast happens, right? If the compiler casts for you, it just did an end-around on your strategy to force a template.

Here we go...
Forcing a reference type in one method signature can be done with "ref":

public void Add(ref Object referenceType)
{
}

// this does not cover all other types
public void Add(ValueType valueType)
{
}

I just tested and when you have only those two method signatures, you have nothing covering a type such as a String. So ValueType appears to be specific to structs.

Tech Off - T == null => Boxing = Problem

jrg — Thu, 10 Mar 2005 20:04:51 GMT

Oh man, you said the word "can't"... and I can't resist the word

Not the same way of course, no. Templates are such a cool OOP tool and the STL serves good testament to that. I think it's just a paradigm shift in C# regarding types as they're all derived from Object and value types from Object then ValueType.

public void Add(ValueType item)
{
}

This should force the developer consuming your method to cast. If they can't cast to a value type then you'd be assured when you do receive an object you're receiving a value type. It's still an object, just limited to a specific type of core object.

I haven't tested this, and in reading, ValueType is stated as the base type for structs whether struct is a subset of ValueType or the defiinition of the set I don't know... 10 second test program time

Tech Off - T == null => Boxing = Problem

jrg — Thu, 10 Mar 2005 12:44:01 GMT

I agree as well. We'd have to hear from the author what the intentions are, or what the problem is.

It was indicated that boxing was seen as a problem. The method appears to be purposely very generic, perhaps for a library. If boxing based performance was a problem where Add involved a significant order of N (huge sorting? crypto?), I think it would be a better path to polymorph and optimize rather than generalize.

Tech Off - Set IIsWebDirectory Permissions via WMI in C#

jrg — Thu, 10 Mar 2005 12:29:19 GMT

Are you on IIS 6.0?

Tech Off - Set IIsWebDirectory Permissions via WMI in C#

jrg — Thu, 10 Mar 2005 05:34:08 GMT

Hi Mark,

Sorry about the wrong tangent!

You'd like to set up an IIS virtual directory through C# and WMI and have the operation perform just like you were doing mmc configuration of a new virtual directory?

Tech Off - Set IIsWebDirectory Permissions via WMI in C#

jrg — Thu, 10 Mar 2005 02:04:48 GMT

Hehe, yeah, this is a fun one.

First, there is a utility (vbscript) available to help you set permissions:
http://support.microsoft.com/kb/267904

Second, if you can avoid using anonymous access, that's best. Use impersonation to tell your ASP code "act like the user that is using this".

I just saw your "NO VBSCRIPT" comment... sorry about that.

I was looking at this exact problem about a month ago because I wanted to stay away from scripts as well. P-Invoke is an ugly but sometimes necessary approach when it comes to ACE/ACL. I know Microsoft is adding new permission toys in 2.0.

This may be of help:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmisdk/wmi/setting_user_security.asp
"Note A NULL ACL in the SECURITY_DESCRIPTOR grants unlimited access to everyone all the time. For more information about the implications of unlimited access, see Creating a Security Descriptor for a New Object."

Tech Off - T == null => Boxing = Problem

jrg — Wed, 09 Mar 2005 19:05:29 GMT

Try testing the type perhaps:
item.GetType().IsValueType;

Tech Off - T == null => Boxing = Problem

jrg — Wed, 09 Mar 2005 18:56:53 GMT

Yeah, null itself of course serves as the placeholder for a reference type pointing nowhere. I'm not putting much thought into this but it seems logical for a null to signify the existence of a reference type operand on the other side of the comparison operator. int x = null; wouldn't make much sense right?