Filter out value in foreach loop if it does not match any values in enum

Question

How can I skip a value in a foreach loop if it does not match any of the values in an specific enum. Ex:

public enum IDs
{
    SomeIdOne = 1001,
    SomeIdTwo = 1002,
    SomeIdThree = 1003
}

// one of the list items(7777) does not match what's in the IDs enum
var SomeIds = new List<IDs>() { 1002,7777,1001 };

// skip that item when looping through the list.
foreach (IDs id in SomeIds)
{
    // do things with id
}

In the past I have used LINQ to filter out 0 in a similar situation, can I do something like that here?

You could execute a LINQ query against SomeIds and then foreach against that filtered list. — David Tansey
– David Tansey, Commented Mar 27, 2015 at 20:24
Possible duplicate: stackoverflow.com/questions/12291953/… — Setsu
– Setsu, Commented Mar 27, 2015 at 20:24
@Stavros_S No, it's asking the underlying question imbedded in yours. In order to filter out values not in the enum you must first be able to tell whether a particular value exists in the enum. Once you know that, your solution boils down to a simple if statement in the loop body. — Setsu
– Setsu, Commented Mar 27, 2015 at 20:40

AlexD · Accepted Answer · 2015-03-27 20:40:56Z

2

Try

foreach(var id in SomeIds.Where(x => Enum.IsDefined(typeof(IDs), x)))
{
    //....
}

If SomeIds is a list of integers, add Cast:

foreach(var id in SomeIds.Where(x => Enum.IsDefined(typeof(IDs), x)).Cast<IDs>())

edited Mar 27, 2015 at 20:40

answered Mar 27, 2015 at 20:32

AlexD

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