Question

I have an array of int values int[] ids.
I have a Datatable DataTable dt
I want to keep only those values in the array that are there in the Datatable column ids

Say int[] ids contain [2,3,4,5]
dt contains [2,3,4,3,4] —ids here may repeat

so output ids will have only [2,3,4]

Pls suggest ways with lambda or linq….

I tried the crude way using two foreachs.

Answer 1

You need the intersection of the 2 collections. Linq as a Intersect method for that.

From the Linq 101 samples:

public void Linq50()
{
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var commonNumbers = numbersA.Intersect(numbersB);

    Console.WriteLine("Common numbers shared by both arrays:");
    foreach (var n in commonNumbers)
    {
        Console.WriteLine(n);
    }
}

You can find more examples here in Linq 101 Samples.