Object or String does not contain definition for Imagebutton

Question

Im trying to put my ImageButton ID in front of Imageurl. So it places the correct image at the correct button. I've saved the ImageButton ID in my database.

Now my problem;

When Im trying to read it out of the database like this:

reader["Appplaats"].ImageUrl = "~/Images/" + reader["Link"] + ".png";

I get the error: 'object' does not contain a definition for 'ImageUrl' and no extension method 'ImageUrl' accepting a first argument...

I've tried to write it to a string with: To.String() but it then says:

'string' does not contain a definition for 'ImageUrl' and no extension method 'ImageUrl' accepting a first argument...

Anyone knows how to solve this?