CODEWITHSUNDEEP
c#
user393267
user393267

Reputation:

Define a condition in a loop, without add an if

I have a loop that is going through each element of a list.

At the moment I have the foreach loop, and inisde, an if that check a variable for the element of the list. If the value is true, I do certain activities, otherwise I move on.

I was wondering if there is some sort of construct, that would allow me to write something like 

foreach (myclass item in itemlist) where ( item.is_red)
{
     ... do something
}

instead than what I have currently

foreach (myclass item in itemlist)
{
    if (item.is_red)
        ... do something
}

From what I recall, the "where" can be used only as constant definition mechanism, like when defining a specific type of class; so it can't be used in the context that I am presenting here. Am I stuck with the if-else inside the loop as only solution?

Upvotes: 3

Views: 139

Answers (4)

Wicher Visser
Wicher Visser

Reputation: 1543

Convert the enumeration to List and use the Where and ForEach LINQ operator:

itemlist.Where(t => t.is_red).ToList().ForEach(t => DoSomething(t));

or

itemlist.Where(t => t.is_red).ToList().ForEach(t => 
{
  // do something
}

Upvotes: 5

knittl
knittl

Reputation: 265231

Almost :)

foreach (var item in (from i in numbers where i.is_red select i))
{
    ... do something
}

There generally is a small performance hit when LINQ is used to iterate over lists or arrays, since an enumerator object is to be created.

Another way to tackle your problem is to use your condition as guard clause. This can reduce nesting and complexity and usually improves readability (although there is also the opinion of not using multiple returns/continues/breaks in a function/loop to keep cyclomatic complexity down):

foreach (var item in itemlist)
{
    if (!item.is_red) { continue; }

    ... do something
}

In the end it probably boils down to company policy/personal preference.

Upvotes: 1

Nasreddine
Nasreddine

Reputation: 37808

You could use LINQ

foreach (myclass item in itemlist.Where(i => i.is_red))
{

    //... do something
}

Upvotes: 3

Ian
Ian

Reputation: 30813

Yes, you could filter what you want iterate with LINQ Where in the collection first:

foreach (myclass item in itemlist.Where(x => x.is_red)) //here is the `Where`
{
    //do your stuffs
}

Upvotes: 1

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