Hi, thanks for your reply...
When you told me to kill the object using that package, I did see how...and then I had an idea:
Before I had copied th code from sample of ESRI like that. I was initializing the Map in Initialize function called in constructor of my Page class:
MobileMapPackage package = await MobileMapPackage.OpenAsync(filepath);
await package.LoadAsync();
MyMapView.Map = package.Maps.First();
In the destructor of the page, I just forced the MyMapView.Map to null...but it was not enough.
NOW, I moved the package variable as private in my page class, and used the private variable in the destructor adding that:
MyMapView.Map = null;
package.Close();
package = null;
The Close call seem to get all the things happy...now I can deleted and replace my files