List<t> findall question

List<t> findall question - predicates?

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mgonzales3 - 22 May 2007 21:09 GMT

I have a List<t> object consisting of objects which in themselves consist of
BindingListViews of objects. When I want to search for a object value I
normally create a foreach loop and increment a counter to provide me a count.

How can I refactor the same function w/o the foreach and use findall instead?

faux data structure:
---------------------
->
| Customers
<t> Orders
| Orders_Details
->

/*start code*/
foreach (Orders _o in _Customers.Orders)
{
if (_o.exists)
i = i + 1;
}

if (i == _Customers.Orders.Count)
mRet = true;
/*end code*/

/*start desired code*/

myList.findall(_o.quantity >1)

/*end desired code*/

I want to take advantage of the Findall method in the generics namespace.

thanks

Reply to this Message

Nicholas Paldino [.NET/C# MVP] - 22 May 2007 21:38 GMT

What is the call to exits on _o? From this code segment,

foreach (Orders _o in _Customers.Orders)
{
if (_o.exists)
i = i + 1;
}

if (i == _Customers.Orders.Count)
mRet = true;

The equivalent using FindAll is:

// See where the orders exists.
List<T> results = _Customers.Orders.FindAll(delegate(Orders _o) { return
_o.exists; });

// If the count is the same between the two, then set mRet = true.
if (_Customers.Orders.Count == results.Count)
// Set mRet to true.
mRet = true;

Of course, if you were setting mRet to false in the event that the count
was not equal, you could just do this:

mRet = (_Customers.Orders.FindAll(delegate(Orders _o) { return
_o.exists; }).Count == _Customers.Orders.Count);

Hope this helps.

Signature

- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com

>I have a List<t> object consisting of objects which in themselves consist
>of
[quoted text clipped - 33 lines]
>
> thanks

Reply to this Message

Ben Voigt - 23 May 2007 00:35 GMT

>I have a List<t> object consisting of objects which in themselves consist
>of
[quoted text clipped - 23 lines]
> mRet = true;
> /*end code*/

This can be made faster in many cases by leaving the loop early:

foreach (Orders _o in _Customers.Orders)
{
if (!_o.exists)
return false;
}
return true;

To get the same result using a predicate, use List<T>.TrueForAll...

mRet = _Customers.Orders.TrueForAll(delegate (Orders o) { return
o.exists; });

BTW, it's usually considered bad practice to use names starting with
underscores, although this maybe isn't as important in C# because there's no
macro substitution possible.

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List<t> findall question - predicates?

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