A few things:
First, don't use a dictionary for your map. Either use a 2D array:
public int[,] map;
Or locate a library that supports a matrix class. Try to not use strings for maps; do your best to use integers as these are incredibly fast and cheap. You can identify the type of tile in the map by just a single easy-to-remember integer identifier. Second, you call into the Microsoft.Xna.Framework namespace. Is this XNA or MonoGame? Also, change the names of functions, classes, namespaces, variables, enumeration files, ... to more informative names.
Second issue: you aren't loading anything in the LoadContent() method and yoru not unloading anything in the UnloadContent method other than the sprites. That is probably why its not working.