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.
use
int[] myIDs = (from d in dt.AsEnumerable() select d.Field<int>("id")).Intersect (ids).ToArray();
For reference see:
d["id"] instead of dt["id"]. In fact, I'd use d.Field<int>("id") to ensure that the LINQ resultset is a IEnumerable<int> instead of IEnumerable<object>. Oh, and replace dt by dt.AsEnumerable().
Dictionary too but please ask a new question and describe the specific goal you want to achieve... please don't forget to upvote/mark as accepted any answer that was of help...You need to create a new array. Arrays are fixed size.
If you want a data structure able to remove an element you need a List. Note that List removal operation have a worst case complexity of O(n).
For your particular problem however i would write something like this:
public int[] MyFunc(DataTable dt, int[] array)
{
Set<int> allowedsIds = new Set<int>();
Fill your set with ids you want to keep
int[] newArray = new int[inputArray.Length];
int newArrayCount = 0;
for (int i = 0; i < inputArray.Length; ++i)
{
if (allowedsIds.Contains(inputArray[i]))
{
newArray[newArrayCount++] = inputArray[i];
}
}
Array.Resize(ref newArray, newArrayCount);
return newArray;
}
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.
Use the Intersect function:
var ids = new[] {2, 3, 4, 5};
var dt = new[] {2, 3, 4, 3, 4};
foreach (var id in ids.Intersect(dt))
{
}
You could create List<int> fromDB and (cycling over dataset) fill it with ids column values.
Then you could use:
List<int> result = ids.Intersect(fromDB).ToList();
