diff bw null and dbnull

Question

What is the diff bw null and dbnull

Pankaj Kumar Choudhary · Answer

Hello @Gaurav Well null is not an instance of any type. Rather it is an invalid reference. However System.DbNull.Value  is a valid reference to an instance of System.DbNull ( System.DbNull is a singleton and System.DbNull.Value gives you a reference to the single instance of that class) that represents nonexistent * values in the database. *We would normally say null  but I don't want to confound the issue. So there's a big conceptual difference between the two. The keyword null represents an invalid reference. The class System.DbNull represents a nonexistent value in a database field. In general we should try avoid using the same thing (in this case null ) to represent two very different concepts (in this case an invalid reference versus a nonexistent value in a database field). Keep in mind this is why a lot of people advocate using the null object pattern in general which is exactly what System.DbNull is an example of.

Manoj Bhoir · Answer

Hi Well null is not an instance of any type . Rather it is an invalid reference. However System.DbNull.Value is a valid reference to an instance of System.DbNull (System.DbNull is a singleton and System.DbNull.Value gives you a reference to the single instance of that class) that represents nonexistent* values in the database. *We would normally say null but I don't want to confound the issue. So there's a big conceptual difference between the two. The keyword null represents an invalid reference. The class System.DbNull represents a nonexistent value in a database field. In general we should try avoid using the same thing (in this case null) to represent two very different concepts (in this case an invalid reference versus a nonexistent value in a database field). Keep in mind this is why a lot of people advocate using the null object pattern in general which is exactly what System.DbNull is an example of. DBNull.Value is what the .NET Database providers return to represent a null entry in the database. DBNull.Value is not null and comparissons to null for column values retrieved from a database row will not work you should always compare to DBNull.Value. Reference : http://stackoverflow.com/questions/4958379/what-is-the-difference-between-null-and-system-dbnull-value

Rajeesh Menoth · Answer

Hi DBNULL is used to check if a certain field in a database is null NULL is used to check if a whole record is not found in the database. Ref : http://stackoverflow.com/questions/4958379/what-is-the-difference-between-null-and-system-dbnull-value