SQL cache dependencies is new technique in ASP.NET 2.0 onwards which can automatically invalidate a cached data object just like a Dataset. when the related data is modified in the database. So for instance if you have a dataset which is tied up to a database tables any changes in the database table will invalidate the cached data object which can be a dataset or a data source.
To enable this we need a syntax that is as follows in visual studio command prompt type the following command
aspnet_regsql -ed -E -d <DBName>