Access Slide in Presentation

Aspose.Slides allows you to access slides in two ways: by index and by ID.

Access Slide by Index

All slides in a presentation are arranged numerically based on the slide position starting from 0. The first slide is accessible through index 0; the second slide is accessed through index 1; etc.

The Presentation class, representing a presentation file, exposes all slides as an ISlideCollection collection (collection of ISlide objects). This C# code shows you how to access a slide through its index:

// Instantiates a Presentation object that represents a presentation file
Presentation presentation = new Presentation("AccessSlides.pptx");

// Gets a slide's reference through its index
ISlide slide = presentation.Slides[0];

Access Slide by ID

Each slide in a presentation has a unique ID associated with it. You can use the GetSlideById method (exposed by the Presentation class) to target that ID. This C# code shows you how to provide a valid slide ID and access that slide through the GetSlideById method:

// Instantiates a Presentation object that represents a presentation file
Presentation presentation = new Presentation("AccessSlides.pptx");

// Gets a slide ID
uint id = presentation.Slides[0].SlideId;

// Accesses the slide through its ID
IBaseSlide slide = presentation.GetSlideById(id);

Change Slide Position

Aspose.Slides allow you to change a slide position. For example, you can specify that the first slide should become the second slide.

1. Create an instance of the Presentation class.
2. Get the slide’s reference (whose position you want to change) through its index
3. Set a new position for the slide through the SlideNumber property.
4. Save the modified presentation.

This C# code demonstrates an operation in which the slide in position 1 is moved to position 2:

// Instantiates a Presentation object that represents a presentation file
using (Presentation pres = new Presentation("ChangePosition.pptx"))
{
    // Gets the slide whose position will be changed
    ISlide sld = pres.Slides[0];

    // Sets the new position for the slide
    sld.SlideNumber = 2;

    // Saves the modified presentation
    pres.Save("Aspose_out.pptx", SaveFormat.Pptx);
}

The first slide became the second; the second slide became the first. When you change a slide’s position, other slides are automatically adjusted.

Set Slide Number

Using the FirstSlideNumber property (exposed by the Presentation class), you can specify a new number for the first slide in a presentation. This operation causes other slide numbers to be recalculated.

1. Create an instance of the Presentation class.
2. Get the slide number.
3. Set the slide number.
4. Save the modified presentation.

This C# code demonstrates an operation where the first slide number is set to 10:

// Instantiates a Presentation object that represents a presentation file
using (Presentation presentation = new Presentation("HelloWorld.pptx"))
{
    // Gets the slide number
    int firstSlideNumber = presentation.FirstSlideNumber;

    // Sets the slide number
    presentation.FirstSlideNumber=10;
    
    // Saves the modified presentation
    presentation.Save("Set_Slide_Number_out.pptx", SaveFormat.Pptx);
}

If you prefer to skip the first slide, you can start the numbering from the second slide (and hide the numbering for the first slide) this way:

using (var presentation = new Presentation())
{
    var layoutSlide = presentation.LayoutSlides.GetByType(SlideLayoutType.Blank);
    presentation.Slides.AddEmptySlide(layoutSlide);
    presentation.Slides.AddEmptySlide(layoutSlide);
    presentation.Slides.AddEmptySlide(layoutSlide);

    // Sets the number for the first presentation slide
    presentation.FirstSlideNumber = 0;

    // Shows slide numbers for all slides
    presentation.HeaderFooterManager.SetAllSlideNumbersVisibility(true);

    // Hides the slide number for the first slide
    presentation.Slides[0].HeaderFooterManager.SetSlideNumberVisibility(false);

    // Saves the modified presentation
    presentation.Save("output.pptx", SaveFormat.Pptx);
}