Update Links to Files in PowerPoint using C#

Question

I am building automated reporting using excel and PowerPoint templates that I am editing in c# before saving to a new file path. My PowerPoint template has objects imbedded that are linked to the excel template (think cell ranges and charts). I would like to programmatically update the excel file that these objects are linked to. This would be equivalent to going into the PowerPoint document, clicking File -> Info -> Edit Links to Files -> Change Source.

I am currently attempting this with the NetOfficeFw.PowerPoint library, but I have so far been unsuccessful. Here is an example of my latest attempt:

public void UpdateLinks(string templatePath, string excelWorkbookPath)
{
     var application = new PowerPoint.Application();
     var presentation = application.Presentations.Open(templatePath, MsoTriState.msoFalse);

     foreach (PowerPoint.Slide slide in presentation.Slides)
     {
          foreach (var shape in slide.Shapes)
          {
               if (ShapeIsLinked(shape))
               {
                    shape.LinkFormat.SourceFullName = excelWorkbookPath;
               }
          }
     }
}

private bool ShapeIsLinked(PowerPoint.Shape shape)
{
     return shape.Type == MsoShapeType.msoLinkedPicture
         || shape.Type == MsoShapeType.msoLinked3DModel
         || shape.Type == MsoShapeType.msoLinkedGraphic
         || shape.Type == MsoShapeType.msoLinkedOLEObject;
}

This throws the error:

NetOffice.Exceptions.PropertySetCOMException (0x80004005): Failed to proceed PropertySet on PowerPoint.LinkFormat=>SourceFullName. ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.InteropServices.COMException: LinkFormat.SourceFullName : Failed.

I am open to other libraries if needed, but preferably open source or cheaper options that could accomplish this. Thanks!

Answer 1

So I figured out that the excel path you pass to SourceFullName must be to an existing file. I was passing a dummy path for testing just to see if it would actually update the path, and I assumed that it wouldn't check to see if the file existed until I actually attempted to open the powerpoint file and update links. That is not the case, it requires a path to an existing file.