Extract PPSM Metadata in C#

// instantiate the Presentation class with path to PPSM file
var presentation = new Aspose.Slides.Presentation("template.ppsm");

// get DocumentProperties object associated with the Presentation object
var properties = presentation.DocumentProperties;

// access and modify custom properties
for (int i = 0; i < properties.CountOfCustomProperties; i++)
{
    // display names and values of custom properties
    System.Console.WriteLine("Custom Property Name : " + properties.GetCustomPropertyName(i));
    System.Console.WriteLine("Custom Property Value : " + properties[properties.GetCustomPropertyName(i)]);

    // modify values of custom properties
    properties[properties.GetCustomPropertyName(i)] = "New Value " + (i + 1);
}

// save your presentation to a file
presentation.Save("output.ppsm", Aspose.Slides.Export.SaveFormat.Ppsm);