GemBox.Presentation
.NET PowerPoint Library

static void Main()
{
    // Set license key to use GemBox.Presentation in Free mode.
    ComponentInfo.SetLicense("FREE-LIMITED-KEY");

    // Create a new empty PowerPoint file.
    var presentation = new PresentationDocument();

    // Add a slide with a text box of size 5 x 5 cm in the top-left corner.
    presentation.Slides.AddNew(SlideLayoutType.Custom)
        .Content.AddTextBox(0, 0, 5, 5, LengthUnit.Centimeter)
        .AddParagraph()
        .AddRun("Hello World!");

    // Save to PPTX file.
    presentation.Save("Presentation.pptx");
}