Find all nearby customers within a given distance using longitude and latitude

Question

I have a db contain customers longitude and latitude, I have a search form in which the user will enter log/lat and distance dropdown contain 50miles, 100miles,.... and when the user click search I want to write a linq query to get all customers from the db which are in this distance radius. How to make this using C# and linq?

Update:
I found this https://stackoverflow.com/a/1654365/20126 but this gives a square not radius

Answer 1

A little modification of my answer to a similar question:

// radius is the distance in meters
var center = new GeoCoordinate(latitude, longitude);
var result = customers.Select(x => new GeoCoordinate(x.Latitude, x.Longitude))
                      .Where(x => x.GetDistanceTo(center) < radius);

You need to add reference to System.Device.dll.

Answer 2

Using haversine formula

User will have current location, customer location and distance So using haversine formula calculate distance (d1) using current location and customer location Then compare calculated distance (d1) with required distance.

Logic is calculated distance <= required distance then it means current customer is in required distance else customer is outside the radial distance