geohash-dotnet 
Easy-to-use and feature-rich geohash library
Demo
https://geohash.azurewebsites.net/
Installation
To use the geohash library in your projects run the following command in the Package Manager Console:
Install-Package geohash-dotnet
Usage Examples
Create a Geohasher object
var hasher = new Geohasher();Encode a latitude and longitude to a geohash
var hash = hasher.Encode(52.5174, 13.409); // default precision 6
var hash2 = hasher.Encode(52.5174, 13.409, 12); // precision 12Decode a geohash to latitude and longitude
var decoded = hasher.Decode("u33dc0");
var latitude = decoded.Item1;
var longitude = decoded.Item2;Get neighbors for a hash
var neighbors = hasher.GetNeighbors("m");
var northNeighbor = neighbors[Direction.North];
var northEastNeighbor = neighbors[Direction.NorthEast]);
var eastNeighbor = neighbors[Direction.East]);
var southEastNeighbor = neighbors[Direction.SouthEast]);
var southNeighbor = neighbors[Direction.South]);
var southWestNeighbor = neighbors[Direction.SouthWest]);
var westNeighbor = neighbors[Direction.West]);
var northWestNeighbor = neighbors[Direction.NorthWest]);Get specific neighbor for a hash
var southEastNeighbor = hasher.GetNeighbor("u33dc0", Direction.SouthEast));Get all 32 subhashes for a hash
var subhashes = hasher.GetSubhashes("u33dc0");Get parent of a hash
var parentHash = hasher.GetParent("u33dbc")