Manage Tags and Custom Data in Presentations in .NET

Overview

This article explains how Aspose.Slides works with tags and custom data in PowerPoint presentations. It briefly outlines how data is stored in PPTX files, notes that presentation-specific data can exist as tags and custom XML parts, and describes tags as key-value string pairs.

It also shows how to read tag values and how to add tags to a presentation, an individual slide, or a shape. In addition, the article covers common tag-management tasks such as clearing all tags, removing a tag by name, and retrieving the list of tag names.

Data Storage in Presentation Files

PPTX files—items with the .pptx extension—are stored in the PresentationML format, which is part of the Office Open XML specification. The Office Open XML format defines the structure for data contained in presentations.

With a slide being one of the elements in presentations, a slide part contains the content of a single slide. A slide part is allowed to have explicit relationships to many parts—such as User Defined Tags—defined by ISO/IEC 29500.

Custom data (specific to a presentation) or user can exist as tags (ITagCollection) and CustomXmlParts (ICustomXmlPartCollection).

Tags are essentially string-key pair values.

Get Values of Tags

In slides, a tag corresponds to the IDocumentProperties.Keywords property. This sample code shows you how to get a tag’s value with Aspose.Slides for .NET for Presentation:

using (Presentation pres = new Presentation("pres.pptx"))
{
   string keywords = pres.DocumentProperties.Keywords;
}

Add Tags to Presentations

Aspose.Slides allows you to add tags to presentations. A tag typically consists of two items:

• the name of a custom property - MyTag
• the value of the custom property - My Tag Value

If you need to classify some presentations based on a specific rule or property, then you may benefit from adding tags to those presentations. For example, if you want to categorize or put all presentations from North American countries together, you can create a North American tag and then assign the relevant countries (the U.S., Mexico, and Canada) as the values.

This sample code shows you how to add a tag to a Presentation using Aspose.Slides for .NET:

using (Presentation pres = new Presentation("pres.pptx"))
{
   ITagCollection tags = pres.CustomData.Tags;
   pres.CustomData.Tags["MyTag"] = "My Tag Value";
}

Tags also can be set for Slide:

using(Presentation pres = new Presentation())
{
    ISlide slide = pres.Slides[0];
    slide.CustomData.Tags["tag"] = "value";
}

Or any individual Shape:

using(Presentation pres = new Presentation())
{
    ISlide slide = pres.Slides[0];
    IAutoShape shape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 10, 100, 50);
    shape.TextFrame.Text = "My text";
    shape.CustomData.Tags["tag"] = "value";
}

Limitations

Tags added via the CustomData.Tags collection are stored only within the PowerPoint file. They are not transferred to the PDF tag structure when the presentation is exported to PDF. Consequently, a custom identifier assigned as a tag cannot be retrieved from the tagged PDF.

Workaround: You can store a custom identifier in the object’s Alt Text (e.g., shape.AlternativeText = "MyId"). After exporting to PDF, the Alt Text may appear in the PDF tag structure.

FAQ

Can I remove all tags from a presentation, slide, or shape in one operation?

Yes. The tag collection supports a clear operation that deletes all key–value pairs at once.

How do I delete a single tag by its name without iterating over the whole collection?

Use the Remove(name) operation on TagCollection to delete the tag by its key.

How can I retrieve the complete list of tag names for analytics or filtering?

Use GetNamesOfTags on the tag collection; it returns an array of all tag names.