How to set Monotouch map between two points - ios

Question

How can I center a map between two points? Sort of like when the native map application generates directions between location A and location B. I'm got a start coordinate and an end coordinate and I'll like to show two pins. I can place the pins in place, but I'm not sure how to set the center of the map.
Do I need to find the math to work out the exact distance from the points and set the map to that location? Is there a built in function for this?
this.currentMapView.SetCenterCoordinate (annotation.Coordinate, true);

Answer 1

Calculating the midpoint between two coordinates needs a simple formula. For example, let's say you have two coordinates: (x1,y1) and (x2,y2).
Their midpoint coordinate is: ( (x1+x2)/2, (y1+y2)/2 ).
So for example, in map coordinates, let's say you have the following start/end points:
a. long: 40, lat: 39
b. long: 41, lat: 38
Their midpoint coordinate is: ( (40+41)/2, (39+38)/2 ) = (40.5, 38.5)
So you set the map view's center coordinate to the outcome of this formula.
I am not aware of a built-in function for calculating this.

Answer 2

Taken from: http://codisllc.com/blog/zoom-mkmapview-to-fit-annotations/
BasicMapAnnotation is inherit class from MKAnnotation
private void GetRegion(MKMapView mapView)
{
var userWasVisible = mapView.ShowsUserLocation;
mapView.ShowsUserLocation = false; // ignoring the blue blip
// start with the widest possible viewport
var tl = new CLLocationCoordinate2D(-90, 180); // top left
var br = new CLLocationCoordinate2D(90, -180); // bottom right
foreach (var an in mapView.Annotations)
{
// narrow the viewport bit-by-bit
CLLocationCoordinate2D coordinate = ((BasicMapAnnotation) an).Coordinate;
tl.Longitude = Math.Min(tl.Longitude, coordinate.Longitude);
tl.Latitude = Math.Max(tl.Latitude, coordinate.Latitude);
br.Longitude = Math.Max(br.Longitude, coordinate.Longitude);
br.Latitude = Math.Min(br.Latitude, coordinate.Latitude);
}
var center = new CLLocationCoordinate2D
{
// divide the range by two to get the center
Latitude = tl.Latitude - (tl.Latitude - br.Latitude)*0.5
,
Longitude = tl.Longitude + (br.Longitude - tl.Longitude)*0.5
};
var span = new MKCoordinateSpan
{
// calculate the span, with 20% margin so pins aren’t on the edge
LatitudeDelta = Math.Abs(tl.Latitude - br.Latitude)*1.2
,
LongitudeDelta = Math.Abs(br.Longitude - tl.Longitude)*1.2
};
var region = new MKCoordinateRegion {Center = center, Span = span};
region = mapView.RegionThatFits(region); // adjusts zoom level too
mapView.SetRegion(region, true); // animated transition
mapView.ShowsUserLocation =
userWasVisible;
}
} ``