public class AddInInfo : ArcGIS.Desktop.Framework.Contracts.PropertyChangedBase, System.ComponentModel.INotifyPropertyChanged  

{
  var addin_infos = FrameworkApplication.GetAddInInfos();
  StringBuilder sb = new();

  foreach (var info in addin_infos)
  {
    if (info == null)
      break;//no add-ins probed

    sb.AppendLine($"Addin: {info.Name}");
    sb.AppendLine($"Description {info.Description}");
    sb.AppendLine($"ImagePath {info.ImagePath}");
    sb.AppendLine($"Author {info.Author}");
    sb.AppendLine($"Company {info.Company}");
    sb.AppendLine($"Date {info.Date}");
    sb.AppendLine($"Version {info.Version}");
    sb.AppendLine($"FullPath {info.FullPath}");
    sb.AppendLine($"DigitalSignature {info.DigitalSignature}");
    sb.AppendLine($"IsCompatible {info.IsCompatible}");
    sb.AppendLine($"IsDeleted {info.IsDeleted}");
    sb.AppendLine($"TargetVersion {info.TargetVersion}");
    sb.AppendLine($"ErrorMsg {info.ErrorMsg}");
    sb.AppendLine($"ID {info.ID}");
    sb.AppendLine("");
  }
  System.Diagnostics.Debug.WriteLine(sb.ToString());
  MessageBox.Show(sb.ToString(), "Addin Infos");
}