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8dc8a6ac-aa9e-47cc-b45e-e128fcec3c57 |
How to: Open a presentation document for read-only access |
office |
o365devx |
o365devx |
conceptual |
11/01/2017 |
medium |
This topic describes how to use the classes in the Open XML SDK for Office to programmatically open a presentation document for read-only access.
You may want to open a presentation document to read the slides. You might want to extract information from a slide, copy a slide to a slide library, or list the titles of the slides. In such cases you want to do so in a way that ensures the document remains unchanged. You can do that by opening the document for read-only access. This How-To topic discusses several ways to programmatically open a read-only presentation document.
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 methods. Several Open methods are provided, each with a different signature. The following table contains a subset of the overloads for the Open method that you can use to open the package.
| Name | Description |
|---|---|
| Open(String, Boolean) | Create a new instance of the PresentationDocument class from the specified file. |
| Open(Stream, Boolean) | Create a new instance of the PresentationDocument class from the I/O stream. |
| Open(Package) | Create a new instance of the PresentationDocument class from the specified package. |
The previous table includes two Open methods that accept a Boolean value as the second parameter to specify whether a document is editable. To open a document for read-only access, specify the value false for this parameter.
For example, you can open the presentation file as read-only and assign it to a PresentationDocument object as shown in the following using statement. In this code, the presentationFile parameter is a string that represents the path of the file from which you want to open the document.
using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, false))
{
// Insert other code here.
} Using presentationDocument As PresentationDocument = PresentationDocument.Open(presentationFile, False)
' Insert other code here.
End UsingYou can also use the second overload of the Open method, in the table above, to create an instance of the PresentationDocument class based on an I/O stream. You might use this approach if you have a Microsoft SharePoint Foundation 2010 application that uses stream I/O and you want to use the Open XML SDK to work with a document. The following code segment opens a document based on a stream.
Stream stream = File.Open(strDoc, FileMode.Open);
using (PresentationDocument presentationDocument =
PresentationDocument.Open(stream, false))
{
// Place other code here.
} Dim stream As Stream = File.Open(strDoc, FileMode.Open)
Using presentationDocument As PresentationDocument = PresentationDocument.Open(stream, False)
' Other code goes here.
End UsingSuppose you have an application that employs the Open XML support in the System.IO.Packaging namespace of the .NET Framework Class Library, and you want to use the Open XML SDK to work with a package read-only. The Open XML SDK includes a method overload that accepts a Package as the only parameter. There is no Boolean parameter to indicate whether the document should be opened for editing. The recommended approach is to open the package as read-only prior to creating the instance of the PresentationDocument class. The following code segment performs this operation.
Package presentationPackage = Package.Open(filepath, FileMode.Open, FileAccess.Read);
using (PresentationDocument presentationDocument =
PresentationDocument.Open(presentationPackage))
{
// Other code goes here.
} Dim presentationPackage As Package = Package.Open(filepath, FileMode.Open, FileAccess.Read)
Using presentationDocument As PresentationDocument = PresentationDocument.Open(presentationPackage)
' Other code goes here.
End Using[!includeStructure]
In the sample code, after you open the presentation document in the using statement for read-only access, instantiate the PresentationPart, and open the slide list. Then you get the relationship ID of the first slide.
// Get the relationship ID of the first slide.
PresentationPart part = ppt.PresentationPart;
OpenXmlElementList slideIds = part.Presentation.SlideIdList.ChildElements;
string relId = (slideIds[index] as SlideId).RelationshipId; ' Get the relationship ID of the first slide.
Dim part As PresentationPart = ppt.PresentationPart
Dim slideIds As OpenXmlElementList = part.Presentation.SlideIdList.ChildElements
Dim relId As String = (TryCast(slideIds(index), SlideId)).RelationshipIdFrom the relationship ID, relId, you get the slide part, and then the inner text of the slide by building a text string using StringBuilder.
// Get the slide part from the relationship ID.
SlidePart slide = (SlidePart)part.GetPartById(relId);
// Build a StringBuilder object.
StringBuilder paragraphText = new StringBuilder();
// Get the inner text of the slide.
IEnumerable<A.Text> texts = slide.Slide.Descendants<A.Text>();
foreach (A.Text text in texts)
{
paragraphText.Append(text.Text);
}
sldText = paragraphText.ToString(); ' Get the slide part from the relationship ID.
Dim slide As SlidePart = CType(part.GetPartById(relId), SlidePart)
' Build a StringBuilder object.
Dim paragraphText As New StringBuilder()
' Get the inner text of the slide.
Dim texts As IEnumerable(Of A.Text) = slide.Slide.Descendants(Of A.Text)()
For Each text As A.Text In texts
paragraphText.Append(text.Text)
Next text
sldText = paragraphText.ToString()The inner text of the slide, which is an out parameter of the GetSlideIdAndText method, is passed back to the main method to be displayed.
Important
This example displays only the text in the presentation file. Non-text parts, such as shapes or graphics, are not displayed.
The following example opens a presentation file for read-only access and gets the inner text of a slide at a specified index. To call the method GetSlideIdAndText pass in the full path of the presentation document. Also pass in the out parameter sldText, which will be assigned a value in the method itself, and then you can display its value in the main program. For example, the following call to the GetSlideIdAndText method gets the inner text in the second slide in a presentation file named "Myppt13.pptx".
Tip
The most expected exception in this program is the ArgumentOutOfRangeException exception. It could be thrown if, for example, you have a file with two slides, and you wanted to display the text in slide number 4. Therefore, it is best to use a try block when you call the GetSlideIdAndText method as shown in the following example.
string file = @"C:\Users\Public\Documents\Myppt13.pptx";
string slideText;
int index = 1;
try
{
GetSlideIdAndText(out slideText, file, index);
Console.WriteLine("The text in the slide #{0} is: {1}", index + 1, slideText);
}
catch (ArgumentOutOfRangeException exp)
{
Console.WriteLine(exp.Message);
} Dim file As String = "C:\Users\Public\Documents\Myppt13.pptx"
Dim slideText As String = Nothing
Dim index As Integer = 1
Try
GetSlideIdAndText(slideText, file, index)
Console.WriteLine("The text in the slide #{0} is: {1}", index + 1, slideText)
Catch exp As ArgumentOutOfRangeException
Console.WriteLine(exp.Message)
End TryThe following is the complete code listing in C# and Visual Basic.