Best way for stepping through rows

[Vayse]

I have a Datatable, dtCustomers. It has several fields. I need to loop
through it, passing only the Customer Code to another function. Function
name is CalcVat.
Does looping through rows have a memory overhead? As in, which is better:

Method A)
For each rowCustomer in dtCustomers.Rows
CalcVat(rowCustomer("CustCode")
Next

Method B)
Dim iLoop as Integer
For iLoop = 0 to dtCustomers.Rows.Count
CalcVat(iLoop).Item("CustCode")
Next

Normally, I use Method A, just want to know which is the most efficient.
Thanks
Vayse

 

[David Browne]

I have a Datatable, dtCustomers. It has several fields. I need to loop
through it, passing only the Customer Code to another function. Function
name is CalcVat.
Does looping through rows have a memory overhead? As in, which is better:

Method A)
For each rowCustomer in dtCustomers.Rows
CalcVat(rowCustomer("CustCode")
Next

Method B)
Dim iLoop as Integer
For iLoop = 0 to dtCustomers.Rows.Count
CalcVat(iLoop).Item("CustCode")
Next

Normally, I use Method A, just want to know which is the most efficient.
Thanks

The most efficient pattern is to use the iterator and a DataColumn
reference.

Dim colCustomer as DataColumn = dtCustomers.Columns("CustCode")
For each rowCustomer in dtCustomers.Rows
CalcVat(rowCustomer(colCustomer)
Next

David

 

[Vayse]

Sorry, Method B should be:

Dim iLoop as Integer
For iLoop = 0 to dtCustomers.Rows.Count
CalcVat(dtCustomers.Rows(iLoop).Item("CustCode")
Next

 

[Cor Ligthert [MVP]]

Vayse,

Between those as you describe is the A the most efficient, but not always
possible.

The method David describes will (if you add that one ")" ) at the end,
inside both method gives probably more performance benefit. For both this is
only worthfull thinking about if you are doing endless times looping through
very huge tables.

(assuming that your method B goes until count-1)

I hope this gives an idea

Cor

 

[Kevin Yu [MSFT]]

Hi Vayse,

I agree to use foreach loop, since the compiler will optimize the loop
process.

Kevin Yu
Microsoft Online Community Support

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