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Disposing of sql connection obeject between functions

Posted on 2010-11-24
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Last Modified: 2012-05-10
Hi,
I have t functions say A() and B(). Currently in each function i create a sql db connection object in each function. Function A() calls function B(). I want to pass the db connection object from A() to B() as a paramter so i can get rid of creating the db connection object in B().
My question is this, do i still need to dipose of the passed db object in B() by using

DBConnection.Dispose()
DBConnection = Nothing

Or can i dispose of it in function A() ?
I am concerned if i close it in B() then it will no longer be valid in A(), this application is multi trheaded and i have to be ver carefull and make sure i dispose of the objects when each thread is done.
hope this makes sense

thanks
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Question by:CraigLazar
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Expert Comment

by:Carl Tawn
ID: 34205364
If you create it in A() and pass a reference to it to B(), then you should dispose of it in A() when B() has finished with it. Partly so that it is still valid if A() needs to use it, but also because it is good practice to dispose an object in the same method/object that created it.
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Author Comment

by:CraigLazar
ID: 34205439
Hi, ok this is how i am declaring it in B()
B(ByVal DBConn As SqlClient.SqlConnection)
so can i still dispose of the passed object in B(), and it will not effect the connection object in A()
The reason is that i have a loopoing process where inside the loop i call B(), so instead of creating another object each time B() is called, i want to just pass it the existing open conneciton object. once the object is passed does it then created as a seperate object in memory that must be disposed of in B().

thanks
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Accepted Solution

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Carl Tawn earned 250 total points
ID: 34205482
You should be passing ByRef rather than ByVal, wo that you are only working with a single instance of the object. You don't need to dispose of it in B() just in A() when you are done with it.

Sequence:
Create and open Connection in A()
Pass reference to B()
B() does some operations using the connection
A() closes/disposes of the connection

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Expert Comment

by:CodeCruiser
ID: 34205546
You can declare the connection at class level so you dont have to pass it to B.
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Author Comment

by:CraigLazar
ID: 34205548
hi, if i use Byval does it create a new object from the passed object in function B()? if so then i would then need to close it in B()?

thanks
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Expert Comment

by:Alpesh Patel
ID: 34205602
If you have passed parameter as reference then no need to dispose it but if passed as byval then need to dispose.

In .net Byval is by default.
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Expert Comment

by:sevensnake77
ID: 34205613
 If (Not conn Is Nothing) Then
            If conn.State <> ConnectionState.Closed Then conn.Close()
            conn.Dispose()
        End If
        If Not cmd Is Nothing Then cmd.Dispose()
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Expert Comment

by:CodeCruiser
ID: 34205646
ByVal only works for primitive types. For object types, it passes a pointer to the object rather than the object. So the object is still being shared rather than duplicated.
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Expert Comment

by:Carl Tawn
ID: 34205671
You are still only dealing with a single object. If A() creates and open the connection the only A() should be closing/disposing of it.
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Expert Comment

by:mastoo
ID: 34206142
If you need another opinion, yes pass byval and create/dispose one time in A() outside of the loop that calls B
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Author Closing Comment

by:CraigLazar
ID: 34281922
thanks
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