PowerPoint Interop: Get Placeholder by Name defined in Master

Question

In my PowerPoint AddIn I want to access shapes on the slides. The shapes are placeholders defined in custom layouts in the slidemaster.

When I add a slide based on the custom layout, the shapes just get named "placeholder 1", "placeholder 2", ...

Is there a way to get the placeholder by the name given in the master?

Currently I am searching shapes with this code:

public static Shape GetShape(string stringToSearch, Shapes shapes) {

        foreach (Shape shape in shapes) {

            if (shape.Name == stringToSearch) {
                return shape;
            }

            // Search Groups
            if (shape.Type == MsoShapeType.msoGroup) {
                foreach (Shape childshape in shape.GroupItems) {
                    if (childshape.Name == stringToSearch) {
                        return childshape;
                    }
                }
            }
        }

        throw new KeyNotFoundException("No Shape found");
}

---

Update: Maybe to make it more clear, this is the structure of the PowerPoint-Presentation.

Master with Names defined for placeholders:

Presentation where names defined in master are lost:

Problem: How to get element in presentation, by name defined in master?

Answer 1

Well.. here is Steve's "Ugly!" solution.

For my project I neither have nor want control over creation of shapes so I cannot "tag" them. That is why I have a custom placeholder name to identify them, So the names of shapes will indeed be [PlaceholderType] ##.

The steps:

• store the locations of all shapes
• reset the slide layout
• match slide shapes and master slide shapes
• restore the locations of all shapes.

Note: I don't use shape groups. this technique will get a lot more complicated if you do and you need to check inside groups.

This is the function that does that and returns a mastershapename - shapename mapping.

private Dictionary<string, string> GetShapeMasters(Powerpoint.Slide s)
{
    Dictionary<string, string> shapeMasters = new Dictionary<string, string>();
    List<ShapeLocation> shapeLocations = new List<ShapeLocation>();

    //store locations
    foreach (Powerpoint.Shape sh in s.Shapes)
    {
        shapeLocations.Add(new ShapeLocation()
        {
            Name = sh.Name,
            Location = new System.Drawing.RectangleF(sh.Left, sh.Top, sh.Width, sh.Height)
        });
    }

    //have powerpoint reset the slide
    //ISSUE: this changes the names of placeholders without content.
    s.CustomLayout = s.CustomLayout;

    //compare slide and master
    foreach (Powerpoint.Shape sh in s.Shapes)
    {
        foreach (Powerpoint.Shape msh in s.CustomLayout.Shapes)
        {
            if (IsShapeMaster(sh, msh))
            {
                shapeMasters[msh.Name] = sh.Name;
            }
        }
    }

    //restore locations
    //TODO: might be replaced by undo
    foreach (var shm in shapeLocations)
    {
        Powerpoint.Shape sh = null;
        try
        {
            sh = s.Shapes[shm.Name];
        }
        catch 
        {
            //Fails for renamed placeholder shapes.
            //Have yet to find a decent way to check if a shape name exists.
        }

        //placeholders do not need to be restored anyway.
        if (sh != null)
        {
            sh.Left = shm.Location.Left;
            sh.Top = shm.Location.Top;
            sh.Width = shm.Location.Width;
            sh.Height = shm.Location.Height;
        }
    }

    return shapeMasters;
}

With this you can do

Dictionary<string, string> shapeMasters = GetShapeMasters(theSlide);
if(shapeMasters.ContainsKey(stringToSearch))
    Powerpoint.Shape KnownShape = theSlide[shapeMasters[stringToSearch]];

And here is the comparison function that takes two shapes and checks if they are "equal". Could be extended to make it more precise.

private bool IsShapeMaster(Powerpoint.Shape sh, Powerpoint.Shape msh)
{
    return
        sh.Left == msh.Left
        && sh.Top == msh.Top
        && sh.Width == msh.Width
        && sh.Height == msh.Height
        && sh.Type == msh.Type
        && sh.PlaceholderFormat.Type == msh.PlaceholderFormat.Type;
}

Little class that stores original shape location

class ShapeLocation
{
    public string Name;
    public System.Drawing.RectangleF Location;
}

I'm open to suggestions because I don't like this, either. Only there seems to be no other way to link shapes and placeholders together. There really isn't some shape.MasterShape we are missing, is there?