ArcGIS for SilverLight之FindGraphicsInHostCoordinates

用DrawObject画框，并选中框框内的图元：

//fLayer为FeatureLayer
double x1,y1,x2,y2;
mapControl.MapToScreen(rc.XMin,rc.YMin,out x1,out y1);
mapControl.MapToScreen(rc.XMax,rc.YMax,out x2,out y2);
//需要将屏幕坐标点转到Application.Current.RootVisual对应的坐标点
var trans = mapControl.TransformToVisual(Application.Current.RootVisual);
//注意：pt1为最小坐标，pt2为最大坐标
var pt1 = trans.Transform(new Point(Math.Min(x1,x2),Math.Min(y1,y2)));
var pt2 = trans.Transform(new Point(Math.Max(x1,Math.Max(y1,y2)));
var ftrs = fLayer.FindGraphicsInHostCoordinates(new Rect(pt1,pt2));

foreach (var ftr in ftrs)
	ftr.Select();