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Delete a slide from a presentation

  • Artykuł

This topic shows how to use the Open XML SDK for Office to delete a slide from a presentation programmatically. It also shows how to delete all references to the slide from any custom shows that may exist. To delete a specific slide in a presentation file you need to know first the number of slides in the presentation. Therefore the code in this how-to is divided into two parts. The first is counting the number of slides, and the second is deleting a slide at a specific index.

Note

Deleting a slide from more complex presentations, such as those that contain outline view settings, for example, may require additional steps.

Getting a Presentation Object

In the Open XML SDK, the PresentationDocument class represents a presentation document package. To work with a presentation document, first create an instance of the PresentationDocument class, and then work with that instance. To create the class instance from the document call one of the Open method overloads. The code in this topic uses the Open method, which takes a file path as the first parameter to specify the file to open, and a Boolean value as the second parameter to specify whether a document is editable. Set this second parameter to false to open the file for read-only access, or true if you want to open the file for read/write access. The code in this topic opens the file twice, once to count the number of slides and once to delete a specific slide. When you count the number of slides in a presentation, it is best to open the file for read-only access to protect the file against accidental writing. The following using statement opens the file for read-only access. In this code example, the presentationFile parameter is a string that represents the path for the file from which you want to open the document.

// Open the presentation as read-only.
using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, false))

To delete a slide from the presentation file, open it for read/write access as shown in the following using statement.

// Open the source document as read/write.
using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, true))

With v3.0.0+ the Close() method has been removed in favor of relying on the using statement. This ensures that the Dispose() method is automatically called when the closing brace is reached. The block that follows the using statement establishes a scope for the object that is created or named in the using statement, in this case presentationDocument.

Basic Presentation Document Structure

The basic document structure of a PresentationML document consists of a number of parts, among which is the main part that contains the presentation definition. The following text from the ISO/IEC 29500 specification introduces the overall form of a PresentationML package.

The main part of a PresentationML package starts with a presentation root element. That element contains a presentation, which, in turn, refers to a slide list, a slide master list, a notes master list, and a handout master list. The slide list refers to all of the slides in the presentation; the slide master list refers to the entire slide masters used in the presentation; the notes master contains information about the formatting of notes pages; and the handout master describes how a handout looks.

A handout is a printed set of slides that can be provided to an audience.

As well as text and graphics, each slide can contain comments and notes, can have a layout, and can be part of one or more custom presentations. A comment is an annotation intended for the person maintaining the presentation slide deck. A note is a reminder or piece of text intended for the presenter or the audience.

Other features that a PresentationML document can include the following: animation, audio, video, and transitions between slides.

A PresentationML document is not stored as one large body in a single part. Instead, the elements that implement certain groupings of functionality are stored in separate parts. For example, all authors in a document are stored in one authors part while each slide has its own part.

ISO/IEC 29500: 2016

The following XML code example represents a presentation that contains two slides denoted by the IDs 267 and 256.

    <p:presentation xmlns:p="…" … > 
       <p:sldMasterIdLst>
          <p:sldMasterId
             xmlns:rel="https://…/relationships" rel:id="rId1"/>
       </p:sldMasterIdLst>
       <p:notesMasterIdLst>
          <p:notesMasterId
             xmlns:rel="https://…/relationships" rel:id="rId4"/>
       </p:notesMasterIdLst>
       <p:handoutMasterIdLst>
          <p:handoutMasterId
             xmlns:rel="https://…/relationships" rel:id="rId5"/>
       </p:handoutMasterIdLst>
       <p:sldIdLst>
          <p:sldId id="267"
             xmlns:rel="https://…/relationships" rel:id="rId2"/>
          <p:sldId id="256"
             xmlns:rel="https://…/relationships" rel:id="rId3"/>
       </p:sldIdLst>
           <p:sldSz cx="9144000" cy="6858000"/>
       <p:notesSz cx="6858000" cy="9144000"/>
    </p:presentation>

Using the Open XML SDK, you can create document structure and content using strongly-typed classes that correspond to PresentationML elements. You can find these classes in the namespace. The following table lists the class names of the classes that correspond to the sld, sldLayout, sldMaster, and notesMaster elements.

PresentationML Element Open XML SDK Class Description
<sld/> Slide Presentation Slide. It is the root element of SlidePart.
<sldLayout/> SlideLayout Slide Layout. It is the root element of SlideLayoutPart.
<sldMaster/> SlideMaster Slide Master. It is the root element of SlideMasterPart.
<notesMaster/> NotesMaster Notes Master (or handoutMaster). It is the root element of NotesMasterPart.

Counting the Number of Slides

The sample code consists of two overloads of the CountSlides method. The first overload uses a string parameter and the second overload uses a PresentationDocument parameter. In the first CountSlides method, the sample code opens the presentation document in the using statement. Then it passes the PresentationDocument object to the second CountSlides method, which returns an integer number that represents the number of slides in the presentation.

// Pass the presentation to the next CountSlide method
// and return the slide count.
return CountSlides(presentationDocument);

In the second CountSlides method, the code verifies that the PresentationDocument object passed in is not null, and if it is not, it gets a PresentationPart object from the PresentationDocument object. By using the SlideParts the code gets the slideCount and returns it.

if (presentationDocument is null)
{
    throw new ArgumentNullException("presentationDocument");
}

int slidesCount = 0;

// Get the presentation part of document.
PresentationPart? presentationPart = presentationDocument.PresentationPart;

// Get the slide count from the SlideParts.
if (presentationPart is not null)
{
    slidesCount = presentationPart.SlideParts.Count();
}

// Return the slide count to the previous method.
return slidesCount;

Deleting a Specific Slide

The code for deleting a slide uses two overloads of the DeleteSlide method. The first overloaded DeleteSlide method takes two parameters: a string that represents the presentation file name and path, and an integer that represents the zero-based index position of the slide to delete. It opens the presentation file for read/write access, gets a PresentationDocument object, and then passes that object and the index number to the next overloaded DeleteSlide method, which performs the deletion.

// Get the presentation object and pass it to the next DeleteSlide method.
static void DeleteSlide(string presentationFile, int slideIndex)
{
    // Open the source document as read/write.
    using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, true))
    {
        // Pass the source document and the index of the slide to be deleted to the next DeleteSlide method.
        DeleteSlide(presentationDocument, slideIndex);
    }
}

The first section of the second overloaded DeleteSlide method uses the CountSlides method to get the number of slides in the presentation. Then, it gets the list of slide IDs in the presentation, identifies the specified slide in the slide list, and removes the slide from the slide list.

// Delete the specified slide from the presentation.
static void DeleteSlide(PresentationDocument presentationDocument, int slideIndex)
{
    if (presentationDocument is null)
    {
        throw new ArgumentNullException(nameof(presentationDocument));
    }

    // Use the CountSlides sample to get the number of slides in the presentation.
    int slidesCount = CountSlides(presentationDocument);

    if (slideIndex < 0 || slideIndex >= slidesCount)
    {
        throw new ArgumentOutOfRangeException("slideIndex");
    }

    // Get the presentation part from the presentation document. 
    PresentationPart? presentationPart = presentationDocument.PresentationPart;

    // Get the presentation from the presentation part.
    Presentation? presentation = presentationPart?.Presentation;

    // Get the list of slide IDs in the presentation.
    SlideIdList? slideIdList = presentation?.SlideIdList;

    // Get the slide ID of the specified slide
    SlideId? slideId = slideIdList?.ChildElements[slideIndex] as SlideId;

    // Get the relationship ID of the slide.
    string? slideRelId = slideId?.RelationshipId;

    // If there's no relationship ID, there's no slide to delete.
    if (slideRelId is null)
    {
        return;
    }

    // Remove the slide from the slide list.
    slideIdList!.RemoveChild(slideId);

The next section of the second overloaded DeleteSlide method removes all references to the deleted slide from custom shows. It does that by iterating through the list of custom shows and through the list of slides in each custom show. It then declares and instantiates a linked list of slide list entries, and finds references to the deleted slide by using the relationship ID of that slide. It adds those references to the list of slide list entries, and then removes each such reference from the slide list of its respective custom show.

// Remove references to the slide from all custom shows.
if (presentation!.CustomShowList is not null)
{
    // Iterate through the list of custom shows.
    foreach (var customShow in presentation.CustomShowList.Elements<CustomShow>())
    {
        if (customShow.SlideList is not null)
        {
            // Declare a link list of slide list entries.
            LinkedList<SlideListEntry> slideListEntries = new LinkedList<SlideListEntry>();
            foreach (SlideListEntry slideListEntry in customShow.SlideList.Elements())
            {
                // Find the slide reference to remove from the custom show.
                if (slideListEntry.Id is not null && slideListEntry.Id == slideRelId)
                {
                    slideListEntries.AddLast(slideListEntry);
                }
            }

            // Remove all references to the slide from the custom show.
            foreach (SlideListEntry slideListEntry in slideListEntries)
            {
                customShow.SlideList.RemoveChild(slideListEntry);
            }
        }
    }
}

Finally, the code deletes the slide part for the deleted slide.

// Get the slide part for the specified slide.
SlidePart slidePart = (SlidePart)presentationPart!.GetPartById(slideRelId);

// Remove the slide part.
presentationPart.DeletePart(slidePart);

Sample Code

Following is the complete sample code in both C# and Visual Basic.

// Get the presentation object and pass it to the next CountSlides method.
static int CountSlides(string presentationFile)
{
    // Open the presentation as read-only.
    using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, false))
    {
        // Pass the presentation to the next CountSlide method
        // and return the slide count.
        return CountSlides(presentationDocument);
    }
}

// Count the slides in the presentation.
static int CountSlides(PresentationDocument presentationDocument)
{
    if (presentationDocument is null)
    {
        throw new ArgumentNullException("presentationDocument");
    }

    int slidesCount = 0;

    // Get the presentation part of document.
    PresentationPart? presentationPart = presentationDocument.PresentationPart;

    // Get the slide count from the SlideParts.
    if (presentationPart is not null)
    {
        slidesCount = presentationPart.SlideParts.Count();
    }

    // Return the slide count to the previous method.
    return slidesCount;
}

// Get the presentation object and pass it to the next DeleteSlide method.
static void DeleteSlide(string presentationFile, int slideIndex)
{
    // Open the source document as read/write.
    using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, true))
    {
        // Pass the source document and the index of the slide to be deleted to the next DeleteSlide method.
        DeleteSlide(presentationDocument, slideIndex);
    }
}
// Delete the specified slide from the presentation.
static void DeleteSlide(PresentationDocument presentationDocument, int slideIndex)
{
    if (presentationDocument is null)
    {
        throw new ArgumentNullException(nameof(presentationDocument));
    }

    // Use the CountSlides sample to get the number of slides in the presentation.
    int slidesCount = CountSlides(presentationDocument);

    if (slideIndex < 0 || slideIndex >= slidesCount)
    {
        throw new ArgumentOutOfRangeException("slideIndex");
    }

    // Get the presentation part from the presentation document. 
    PresentationPart? presentationPart = presentationDocument.PresentationPart;

    // Get the presentation from the presentation part.
    Presentation? presentation = presentationPart?.Presentation;

    // Get the list of slide IDs in the presentation.
    SlideIdList? slideIdList = presentation?.SlideIdList;

    // Get the slide ID of the specified slide
    SlideId? slideId = slideIdList?.ChildElements[slideIndex] as SlideId;

    // Get the relationship ID of the slide.
    string? slideRelId = slideId?.RelationshipId;

    // If there's no relationship ID, there's no slide to delete.
    if (slideRelId is null)
    {
        return;
    }

    // Remove the slide from the slide list.
    slideIdList!.RemoveChild(slideId);

    // Remove references to the slide from all custom shows.
    if (presentation!.CustomShowList is not null)
    {
        // Iterate through the list of custom shows.
        foreach (var customShow in presentation.CustomShowList.Elements<CustomShow>())
        {
            if (customShow.SlideList is not null)
            {
                // Declare a link list of slide list entries.
                LinkedList<SlideListEntry> slideListEntries = new LinkedList<SlideListEntry>();
                foreach (SlideListEntry slideListEntry in customShow.SlideList.Elements())
                {
                    // Find the slide reference to remove from the custom show.
                    if (slideListEntry.Id is not null && slideListEntry.Id == slideRelId)
                    {
                        slideListEntries.AddLast(slideListEntry);
                    }
                }

                // Remove all references to the slide from the custom show.
                foreach (SlideListEntry slideListEntry in slideListEntries)
                {
                    customShow.SlideList.RemoveChild(slideListEntry);
                }
            }
        }
    }

    // Get the slide part for the specified slide.
    SlidePart slidePart = (SlidePart)presentationPart!.GetPartById(slideRelId);

    // Remove the slide part.
    presentationPart.DeletePart(slidePart);
}

See also