IsDBNull problem handling

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C#

ASP.NET

What is the differece between IsDBNull and IsNull?

Posted 21-May-12 21:00pm

sunandandutt

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4 solutions

Solution 3

The IsDBNull method tests whether the value parameter is equal to DBNull.Value & returns an indication whether the specified object is of type DBNull.

The System.DBNull value indicates that the Object represents missing or nonexistent data.
DBNull is not the same as Nothing, which indicates that a variable has not yet been initialized.
DBNull is also not the same as a zero-length string (""), which is sometimes referred to as a null string.

DBNull returns True if the data type of Expression evaluates to the DBNull type; otherwise, IsDBNull returns False.

IsNull
Replaces NULL with the specified replacement value.
Please refer: ISNULL (Transact-SQL)[^]

Additional info:
Learn the differences between Is Null and IsNull()[^]

Posted 21-May-12 21:36pm

Prasad_Kulkarni

Comments

Wendelius 22-May-12 16:30pm

Also a good answer

Prasad_Kulkarni 23-May-12 0:04am

Thank you Mika!

Solution 1

If object is null, then it has no value, on the other hand DBNull is value.

Posted 21-May-12 21:05pm

Tomas Ruksenas

Solution 4

the object which is declared but not initialized is null
and
the value retirves from database is null is called DBNull
Null value of database is always DBNull not null

C#

int ob;
DataSet ds ;
DataTable tbl;

the value of above object is null

but
the value in database is null here retrive DBNull of below statement

C#

ds.Tables[0].Rows[0][0]

Posted 21-May-12 21:39pm

Technoses

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VJ Reddy · Accepted Answer · 2012-05-21T21:09:00

In database like Sql Server NULL represents a non existant value. Whereas null in C# represents if an object reference is not set.

ISNULL is Sql Server function as explained here http://msdn.microsoft.com/en-us/library/ms184325.aspx[^] and checks for this non existent value.

In C# the non existent value cannot be compared to null. Hence, a class DBNull is provided in .NET as explained here http://msdn.microsoft.com/en-us/library/system.dbnull.aspx[^]

The IsDBNull is the method of this DBNull class as explained here
http://msdn.microsoft.com/en-us/library/tckcces5(v=vs.71).aspx[^]
to test whether the data is non existent or missing.