Maybe you work with Oracle as well as SQL server 2005 and you use Oracle Spatial and Oracle Locator. Well there is a way to implement this in SQL Server 2005.
Read the article "Using Table Valued Functions in SQL Server 2005 to Implement a Spatial Data Library" on MSDN.
This article explains how to add spatial search functions (point-near-point and point in polygon) to Microsoft SQL Server 2005 using C# and table-valued functions. It is possible to use this library to add spatial search to your application without writing any special code. The library implements the public-domain C# Hierarchical Triangular Mesh (HTM) algorithms from Johns Hopkins University. That C# library is connected to SQL Server 2005 using a set of scalar-valued and table-valued functions. These functions act as a spatial index.