Problem With Isnull. Need To Substitute Null If A Var Is Null And Compare It To Null And Return True

Hey. I need to substitute a value from a table if the input var is null. This is fine if the value coming from table is not null. But, it the table value is also null, it doesn't work. The problem I'm getting is in the isnull line which is in Dark green color because @inFileVersion is set to null explicitly and when the isnull function evaluates, value returned from DR.FileVersion is also null which is correct. I want the null=null to return true which is why i set ansi_nulls off. But it doesn't return anything. And the select statement should return something but in my case it returns null. If I comment the isnull statements in the where clause, everything works fine. Please tell me what am I doing wrong. Is it possible to do this without setting the ansi_nulls to off??? Thank you

set ansi_nulls off


go

declare

@inFileName VARCHAR (100),

@inFileSize INT,

@Id int,

@inlanguageid INT,

@inFileVersion VARCHAR (100),

@ExeState int

set @inFileName = 'A0006337.EXE'

set @inFileSize = 28796

set @Id= 1

set @inlanguageid =null

set @inFileVersion =NULL

set @ExeState =0

select Dr.StateID from table1 dR

where

DR.[FileName] = @inFileName

AND DR.FileSize =@inFileSize

AND DR.FileVersion = isnull(@inFileVersion,DR.FileVersion)

AND DR.languageid = isnull(@inlanguageid,null)

AND DR.[ID]= @ID

)

go

set ansi_nulls on