How to get the title of a presentation of a powerpoint app C#

using Powerpoint = Microsoft.Office.Interop.PowerPoint;      
Powerpoint.Application wdApp = new Powerpoint.Application();
    string oldCaption = wdApp.Application.Caption ;
    string guid = Guid.NewGuid().ToString();
    //set caption to random value
    wdApp.Application.Caption = guid;
    //create a presentation
    PresentationpptPresentation=wdApp.Presentations.Add(Microsoft.Office.Core.MsoTriState.msoTrue);
    //make sure app is visible:
    wdApp.Visible = true;
    //find random value to get process id
    //here I need to get the title of the presentation
    int processId = GetProcessIdByWindowTitle(guid);

    //reset caption
    wdApp.Application.Caption = oldCaption;

    //create a dictionary
    Dictionary<int, Button> mapping = new Dictionary<int, button>();
    //add mapping
    mapping.Add(new KeyValuePair<int, Button>(processId, deleteButton));







    //found this online:
    /// <summary>
    /// Returns the name of that process given by that title
    /// </summary>
    /// <param name="AppId">Int32MaxValue re
    public static int GetProcessIdByWindowTitle(string AppId)
    {
       Process[] P_CESSES = Process.GetProcesses();
       for (int p_count = 0; p_count < P_CESSES.Length; p_count++)
       {
            if (P_CESSES[p_count].MainWindowTitle.Equals(AppId))
            {
                        return P_CESSES[p_count].Id;
            }
       }

        return Int32.MaxValue;
    }