asp.net - Using LINQ find nearby places from database -

we want receive list of nearby places database using linq in asp.net 2012 , feedback on our strategy.

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my table , fake data:

     placeid    name       latitude   longitude         1                   18.1        20.1        2          b          18.2        20.2        3          c          18.3        20.3 

1) in our project client current location (latitude , longitude) taken input

2) @ server side ,depending upon client current location, need find nearby places database using linq

here's code sql earlier used , want use linq.

select  name, latitude, longitude ,    ( 3959 * acos( cos( radians(?) )* cos( radians( latitude) ) * cos( radians( longitude ) - radians(?) )   + sin( radians(?) ) * sin( radians( latitude) ) ) ) distance  table_name  having distance < ?  order distance limit 0 , 20 

[but question how write such query in linq.]

my work on this:

while searching solution, came across code

        var value1 = 57.2957795130823d;         var value2 = 3958.75586574d;          var searchwithin = 20;      double latitude = conversionhelper.safeconverttodoublecultureind(latitude, 0),           longitude = conversionhelper.safeconverttodoublecultureind(longitude, 0);      var location = (from l in sdbml.places                     let temp = math.sin(convert.todouble(l.latitude) / value1) *  math.sin(convert.todouble(latitude) / value1) +                              math.cos(convert.todouble(l.latitude) / value1) *                              math.cos(convert.todouble(latitude) / value1) *                              math.cos((convert.todouble(longitude) / value1) - (convert.todouble(l.longitude) / value1))                          let calmiles = (value2 * math.acos(temp > 1 ? 1 : (temp < -1 ? -1 : temp)))                          (l.latitude > 0 && l.longitude > 0)                          orderby calmiles                         select new location                              {                                     name = l.name                                 });                         return location .tolist(); 

but problem ,how reference conversionhelper or under namespace comes.

all advice appreciated.

so, if want calculate distance between 2 co-ordinates, why don't use dot net's geocoordinate?

it goes

 var firstcordinate = new geocoordinate(latitude1, longitude1);  var secondcordinate = new geocoordinate(latitude2, longitude2);   double distance = firstcordinate.getdistanceto(secondcordinate); 

you can find inside namespace system.device.location.

so save math.cos , math.sin , linq plain , simple. (probably foreach loop do)

so entire query can summarized as:

list<location> locations = new list<location>(); foreach(var place in sdbml.places) {    //your logic compare various place's co-ordinates of    //user's current co-ordinate }