How to get the properties from a dynamic (Anonymous Type) object using reflection?

Question

I know there are many questions asked on this topic here on Stack Overflow, but I couldn't find any concrete answer to my current situation.

1. I have a dynamically generated collection of rows.
2. The property names (the columns, and the number of columns) are only known at run time.

3. I have the following code,

   // collection gets populated at run time, the type T is dynamic.
   public void GenerateExcel<T>(string filename, IEnumerable<T> collection)
   {
       // Since the T passed is dynamic Type I am facing issues in getting
       // the property names.
       var type = typeof(T); // the type T is an anonymous type, and thus
                             // the 'type' variable is always an Object type.
       var columns = type.GetProperties().Length; // when I run this line it
                                                  // is obvious the properties 
                                                  // returned is always 0 so how
                                                  // do I get the properties?
   
       /* Implementation omitted */
   }
   

4. I am calling the above method with the code below,

   GenerateExcel<dynamic>(
       "filename.xls",
       new[] { 
           new { Obj1 = "a", Obj2 = 1, Obj3 = 3.1, Obj4 = new DateTime(2014, 1, 1) }, 
           new { Obj1 = "b", Obj2 = 2, Obj3 = 3.2, Obj4 = new DateTime(2014, 1, 2) },
           new { Obj1 = "c", Obj2 = 3, Obj3 = 3.3, Obj4 = new DateTime(2014, 1, 3) },
           new { Obj1 = "d", Obj2 = 4, Obj3 = 3.4, Obj4 = new DateTime(2014, 1, 4) },
       } // these objects (Obj1, Obj2 ... (columns) are generated dynamically at run time).
   );
   

The same question was asked multiple times, here at Stack Overflow, but the solution is only when you have known property names, for example

1. Get property value from C# dynamic object by string (reflection?)
2. How to access property of anonymous type in C#? // property can be accessed only when the property name is known in advance.

Any help is greatly appreciated!

Answer 1

Get the first item, cast it to object, and then you can get the properties:

object e = collection.FirstOrDefault();
var columns = e.GetType().GetProperties().Length;

Or just:

collection.FirstOrDefault().GetType().GetProperties().Length;

Answer 2

Can you use this?

 dynamic dy = obj;
 Console.WriteLine(dy.param);