LINQ request [closed]

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Closed 3 years ago.

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How to do this?

int[] mas={1,2,3,4,...,n}

public var method1(mas)
{
var d = from i in Object where i.number==mas[0] || i.number==mas[1] || i.number==mas[2]|| ... || i.number==mas[n] select i;
return d;
}

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You will want to do something like this

var d = From i in Object
        From n in mas
        Where n == i.Number
        Select i;
return d;

Actually now that I think about that, that is going to return to you a list of i for every match.

You probably were looking for something more like

   //create a list for the items that match the criteria
    List<ObjectToGet> d = new List<ObjectToGet>;

    //Loop over each item in your Object
    foreach(ObjectToGet objectItem in Object){
        //If the item contains any match add it to the list
        if((From n in mas Where n == d.Number Select n).Any){
            d.Add(objectItem);
        }
    }

    return d;

There's probably a way to write this in pure LINQ but this is conceptually what you are trying to do

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Wrap your mas into HashSet by using constructor and use Contains

Check this article as inroduction: Introducing HashSet (Kim Hamilton)

So you'll end with something like that:

 int[] mas={1,2,3,4,...,n};
 var set = new HashSet<int>(mas); // or you can init set with proper value without array

 public var method1(mas)
 {
    var d = from i in Object where set.Contains(i.number) select i;
    return d;
 }

Pure LINQ solution is good too (@msarchet) when you have small enough source array.