#region Namespaces
using System;
using System.Collections.Generic;
using System.Diagnostics;
using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
#endregion

namespace RevitAddin1
{
    [TransactionAttribute(TransactionMode.ReadOnly)]
    public class Command : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData,ref string message,ElementSet elements)
        {
            UIApplication uiapp = commandData.Application;
            UIDocument uidoc = uiapp.ActiveUIDocument;
            Application app = uiapp.Application;
            Document doc = uidoc.Document;

            Selection sel = uidoc.Selection;


            foreach (ElementId eleid in sel.GetElementIds())
            {

                Element ele = doc.GetElement(eleid);
                System.Text.StringBuilder paramValue = new System.Text.StringBuilder();

                foreach (Parameter param in ele.Parameters)
                {
                    paramValue.AppendFormat("{0}: ", param.Definition.Name);

                    switch (param.StorageType)
                    {
                        
                        case StorageType.Integer:
                            paramValue.AppendFormat("{0:N}", param.AsInteger());
                            break;
                        case StorageType.Double:
                            paramValue.AppendFormat("{0:0.00}", param.AsDouble());
                            break;
                        case StorageType.String:
                            paramValue.Append(param.AsString());
                            break;
                    }
                    paramValue.AppendLine();
                }
                TaskDialog.Show(ele.Name, paramValue.ToString());
            }

            return Result.Succeeded;
        }
    }
}