Presentation ppt = new Presentation();
 ppt.LoadFromFile(inputFile);
 StringBuilder sb = new StringBuilder();
 ISlide slide = ppt.Slides[0];
 for (int i = 0; i < slide.Shapes.Count; i++)
 {
     IShape shape = slide.Shapes[i];
     if (shape is IAutoShape)
     {
         IAutoShape autoshape = slide.Shapes[i] as IAutoShape;
         string text = autoshape.TextFrame.Text;
         //obtain the text position information
         PointF point = autoshape.TextFrame.GetTextLocation();
         sb.AppendLine("Shape " + i + "：" + text + "\r\n" + "location：" + point.ToString());
     }
 }
 File.AppendAllText(outputFile, sb.ToString());
 ppt.Dispose();

Presentation ppt = new Presentation();
ppt.LoadFromFile(inputFile);
ISlide slide = ppt.Slides[0];
IAutoShape autoshape = slide.Shapes[0] as IAutoShape;
IList lines = autoshape.TextFrame.GetLayoutLines();
for (int i = 0; i < lines.Count; i++)
{
   float ascent= lines[i].Ascent;
   float descent = lines[i].Descent;
}

Presentation ppt = new Presentation();
ppt.LoadFromFile("FreeForm.pptx");
ISlide slide = ppt.Slides[0];
int num = 0;
foreach (IShape shape in slide.Shapes)
{
    byte[] svgByte = shape.SaveAsSvg();
    FileStream fs = new FileStream("shape_" + num + ".svg",FileMode.Create);
    fs.Write(svgByte, 0, svgByte.Length);
    fs.Close();
    num++;
}