Kind regards - Jakob
P.S. Sorry for the late answer, for some reason WordPress stopped notifying me of comments ... :-/

http://www.xnafan.net/downloads/_tutorials/dragandswap/dragandswaptotilessolution.zip

Kind regards - Jakob

*** I KEY ***

I am guessing you want to show an inventory when the "I" key has been pressed? And then remove it again when the "I" key is pressed again?

For this you will need a boolean variable (e.g. "inventoryVisible"), which you toggle when the "I" key is pressed.
The easiest way to do this is:

inventoryVisible = !inventoryVisible;

which takes the opposite value of what is in the boolean variable and stores it again.

You will need to store both the current KeyboardState and the previous KeyboardState to make sure you don't just toggle (switch values) for every Update(), but only when "I" key was up in the previous Update() and down in this one.

*** Swap items ***
For this to work, you will have to
- store the original position of the item you grab with the mouse
- check when you drop an item, whether it is on top of another one

One way to check for overlap when dropping is to create two bounding rectangles, one for each item, and use the Rectangle.Intersects method (http://msdn.microsoft.com/en-us/library/microsoft.xna.framework.rectangle.intersects.aspx) to check whether one item overlaps the other.
This way you can just set position of the item that is being dropped on to the original position of the dragged item.
If you want all items to stay in a grid, have a look at the Drag and Drop with snap to tiles tutorial:
http://xnafan.net/2012/07/simple-drag-and-drop-with-snap-to-tiles-in-xna/

Kind regards - Jakob

But, i have a couple of questions to you.

How do you make the items will be visible only if the I in the keyboard is pressed? and how do you make when the item 1 in the inventory is dragged to the item 2, the item 2 will be moving to the item slot 1 instead of they are overlapping each other.

I am looking forward for it.. Thank you very much 😀 😀