WPSC in MOSS 2007 - "Cannot retrieve properties at this time. "

Introduction

Web Part Service Component (WPSC) is a nice feature for SharePoint developers working on client side programming. It supplies SharePoint Web Part objects combined with HTML objects for developers to practice on web part management.

Background

There seems not so much changes on the object level between SharePoint 2003 and SharePoint 2007. There is one more property in WPSC 3.0 than WPSC 2.0 called WebServerRelativeURL. But things seems not so simple because the way WPSC registers Web Parts has changed...

In WSS 2.0, WPSC registers a Web Part using tokens like WPQ1, WPQ2, WPQ3 ...

WPSC.Init(document);
var varPartWPQ7 = WPSC.WebPartPage.Parts.Register('WPQ7',
    '6b93d728-6d3e-47cb-9917-37cfd0aff443',document.all.item('WebPartWPQ7'));
var varPartWPQ3 = WPSC.WebPartPage.Parts.Register('WPQ3',
    '32950565-92aa-4a11-92b0-9dcff1b4e956',document.all.item('WebPartWPQ3'));
var varPartWPQ2 = WPSC.WebPartPage.Parts.Register('WPQ2',
    '338c0c38-b8cb-4ea2-918e-2d5c632df2bd',document.all.item('WebPartWPQ2'));
var varPartWPQ4 = WPSC.WebPartPage.Parts.Register('WPQ4',
    '3612bf7c-595c-48fe-aaf4-87cbb89078a2',document.all.item('WebPartWPQ4'));
var varPartWPQ5 = WPSC.WebPartPage.Parts.Register('WPQ5',
    '43bf7599-0acf-41d7-b3f5-397cbc7eca6b',document.all.item('WebPartWPQ5'));
var varPartWPQ6 = WPSC.WebPartPage.Parts.Register('WPQ6',
    '4623b8c7-989f-471c-a3fa-7f53148acdcd',document.all.item('WebPartWPQ6'));
var varPartWPQ1 = WPSC.WebPartPage.Parts.Register('WPQ1',
    '056d0533-514b-42e1-8925-38bf2c5b3b07',document.all.item('WebPartWPQ1'));

In WSS 3.0, WPSC registers a Web Part using the same tokens as WSS 2.0, but WPQ1 is used for register a null Web Part. If you try to access its properties, you will get an error: "Cannot retrieve properties at this time".

var varPartWPQ4 = WPSC.WebPartPage.Parts.Register('WPQ4',
    'e2412c24-1c4f-4545-93dc-2a4e965b2032',document.all.item('WebPartWPQ4'));
var varPartWPQ5 = WPSC.WebPartPage.Parts.Register('WPQ5',
    '77cbc2a3-c770-4a7d-9024-63b78cc45ff4',document.all.item('WebPartWPQ5'));
var varPartWPQ6 = WPSC.WebPartPage.Parts.Register('WPQ6',
    'f4481df0-a93d-495d-bcb6-fa686bbd9816',document.all.item('WebPartWPQ6'));
var varPartWPQ7 = WPSC.WebPartPage.Parts.Register('WPQ7',
    '1fddcba4-7b65-40d9-972f-d6ee86a224f4',document.all.item('WebPartWPQ7'));
var varPartWPQ1 = WPSC.WebPartPage.Parts.Register('WPQ1',
    '00000000-0000-0000-0000-000000000000',document.all.item('WebPartWPQ1')); 

Let's go through a sample code which will collect the Web Part titles:

if(typeof(WPSC) == 'undefined')
    return;
  
if(WPSC.WebPartPage)
    PortalPartsCollection = WPSC.WebPartPage.Parts; 
 
if(PortalPartsCollection) 
{ 
    for(var i=0; i< PortalPartsCollection.Count; i++) 
    { 
        var objWebPart = PortalPartsCollection.Item(i); 
    
        if(objWebPart.WebPartQualifier == "WPQ1")
            continue;
    
        if(objWebPart.Properties.Count() > 0)
        {  
            var webpartTitle = 
              objWebPart.Properties.Item("http://schemas.microsoft" + 
                                         ".com/WebPart/v2#Title").Value;
            PortalPartsTitleCollection.push(webpartTitle);
    
            var targetObject = searchTargetNode(objWebPart);
            if(targetObject)
            targetObject.innerHTML = createArchor(webpartTitle) + targetObject.innerHTML;
        }   
    } 
}

In the code above, we can see that the Web Part with WebPartQualifier "WPQ1" will be ignored.

History

This is the first version.