C# check if COM Object is available before performing some action on them

ccomobject

How can i check if COM Object exists (is registered / is available / can run without problems) before running actions using them?

My application should use other applications COM's (InteropServices) but before i start some action, i would like to check whether i can create COM objects.

It woudnt be a problem if COM's where in same directory, but they're not.

In excample.
I would like to check if sth like this:

CDNBase.ApplicationClass App = new CDNBase.ApplicationClass();

will cause catchable exceptions or something. Than i could create nice MessageBox and block some events till it will be fixed.
Any other solutions like checking if namespace exists or sth, are also ok (i guess 😀 )

I tried to use try / catch, but it fails, google didnt bring me anything special on this, so im asking for your help.

Thanks in advance

Best Answer

Have you tried catching ComException:

try
{
...
}
catch(System.Runtime.InteropServices.COMException ex)
{
    // log error message
    throw;
}

UPDATE: apologies, I wasn't suggesting to suppress the exception. Have updated.

Alternatively, you could search in the registry for the component's ClassID:

HKEY_CLASSES_ROOT\CLSID\{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}\InprocServer32

The default value will contain the filesystem full path to the DLL.

Related Solutions

.net – the best way to detect if a COM component is installed

I think the best way, unfortunately, is to try and instantiate it. Checking in the registry does not guarantee that the component is actually there at all (e.g. the file may have been deleted or moved post registration).

Javascript – How to check if a JavaScript Object is a DOM Object

This might be of interest:

function isElement(obj) {
  try {
    //Using W3 DOM2 (works for FF, Opera and Chrome)
    return obj instanceof HTMLElement;
  }
  catch(e){
    //Browsers not supporting W3 DOM2 don't have HTMLElement and
    //an exception is thrown and we end up here. Testing some
    //properties that all elements have (works on IE7)
    return (typeof obj==="object") &&
      (obj.nodeType===1) && (typeof obj.style === "object") &&
      (typeof obj.ownerDocument ==="object");
  }
}

It's part of the DOM, Level2.

Update 2: This is how I implemented it in my own library: (the previous code didn't work in Chrome, because Node and HTMLElement are functions instead of the expected object. This code is tested in FF3, IE7, Chrome 1 and Opera 9).

//Returns true if it is a DOM node
function isNode(o){
  return (
    typeof Node === "object" ? o instanceof Node : 
    o && typeof o === "object" && typeof o.nodeType === "number" && typeof o.nodeName==="string"
  );
}

//Returns true if it is a DOM element    
function isElement(o){
  return (
    typeof HTMLElement === "object" ? o instanceof HTMLElement : //DOM2
    o && typeof o === "object" && o !== null && o.nodeType === 1 && typeof o.nodeName==="string"
);
}

Best Answer

Related Solutions

.net – the best way to detect if a COM component is installed

Javascript – How to check if a JavaScript Object is a DOM Object

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