Question

I have an application that reads and writes to table in SQL Server 2005. I know the basics of reading and writing to a table.

If there is no Id then I create a new entry. If there is an Id I update the existing entry.

What is the best way to write the SqlCommand string based upon if it already exists or is new?

I can’t see writing two methods when it would then take updating two places when it came time for changes.

Any tips or tricks would be appreciated.

Answer 1

Here is full sample of working code you need , all you need to do is check if record already exists then update it or just insert it.

create table MyEntity(id int,val varchar(20))
Go
create proc SaveMyEntity(@id int, @val varchar(20))
as
If Exists (Select ID from MyEntity where Id = @ID)
Update MyEntity
       Set val = @val
       Where ID = @ID
else
Insert into MyEntity values(@ID,@val)

-- here is proof of insertion/updation

Go 
SaveMyEntity 1,'a'
Go
SaveMyEntity 1,'b'
Go
SaveMyEntity 2,'a'
Go
select * from myEntity

Results will be

 id val
1   b
2   a

Then you can use this stored proc from your SqlCommand in C# (recommended)

Or your can just use this SQL statement from your C# SqlCommand (not recommended and tested)

If Exists (Select ID from MyEntity where Id = @ID)
Update MyEntity
       Set val = @val
       Where ID = @ID
else
Insert into MyEntity values(@ID,@val)