Inserting Picture (from Web- through Webdav) to Word document using VSTO code

Question

Hi,
I have been trying to insert an image/picture to current selection in word. with help of code -
Microsoft.Office.Interop.Word.InlineShape s = this.Application.Selection.InlineShapes.AddPicture(
@"http://127.0.0.1:9001/test/myimage.png", true, true, Type.Missing);
This code works fine if image is on desktop or network shared location but some issues for URL exposed through Webdav.
On inserting the picture word shows - "The linked image cannot be displayed....." message. If we close and open word document again then image appears properly.
Some observations:
1. If we use same option through Ribbon  "Insert -> Picture -> Enter path and click on "Link to File" then we get Prompt for Wevdav password (Only once, later Word caches it) and linked images appear properly.
2. Updating the shape explicitly wouldnt help. 
s.LinkFormat.Update();
What we are looking for is, Does Ribbon "Insert" functionality do something additional to prompt Webdav authentication to cache? if we want to achieve the same? what needs to be invoked before we make call to AddPicture API?
Thanks
H

Answer 1

Thanks for the response.. 
No, when document is opened again, then you dont need to enter the password. 
Somehow on document open event MS word knows how to retreive password from cookie for given domain.
When you insert the image using ribbon -> insert picture option, 
MS Word first looks into cache if the domain cokkie already available then bypass authentication/password prompt
Otherwise it would show the prompt and store the cookie in cache again.
The mystry is how MS-Word interacts with this "cached cookies"
while doing more reading on this, it seems MS Word has been using Klink.dll for this kind of functionality https://support.microsoft.com/en-us/kb/899927 but it would be great if you can provide more pointers.
>>Could you share an image link of Webdav?
Since, it's my local webdav server, you would not be able to access the image link, may be you can upload an image to sharepoint (as sharepoint also supports webdav) and use that for reproducing this problem at your end.
Thanks
H