There are a lot of different geographic coordinate systems. The most commonly used is WGS84 (EPSG:4236). Google Maps uses it's own spherical mercator projection which is commonly known as Google Mercator, but its latlong values are WGS84 coordinates.
In order to transform your coordinates you have to know the source and destination coordinate system. Once you have figured this out you can use a library like Proj4js to calculate the transformation.
Proj4js also provides an online coordinate calculator, which might help you to figure out which coordinates system the coordinates in your database are using.
If you are looking for a C# framework: SharpMap is great for handling all aspects of geospatial applications.