Unity / Search closes Object from a List by tag - unity3d

Question

I have a Problem to find the closest Object in my List.
There are three types with the tags (Food, Stone and Wood).
I spawn them at the beginning , some for each type, if i found some Resources, they're not hidden anymore, and i add them to the List that a Worker goes to them and harvests them.
So Later in the Game, for expample
i found 3 Stone Resources, then worker should harvest the closest one first everytime....
but i don't know how to iterate throw a Loop only to search for the Tags and how to get the position of the closest one.
Here is some code of the Method that i wrote:
void FindNearestFoodRessource()
{
for (int i = 0; i < gameController.discoveredRessources.Count; i++)
{
//float dist = Vector3.Distance(gameController.discoveredRessources[i].transform.position, transform.position);
GameObject nearestFoodRessource = GameObject.FindGameObjectWithTag("Food");
}
}

Answer 1

First thing first - don't use FindGameObject**** in frequently called methods, it is very expensive.
About your problem - just check tag and distance of all the resources:
float minDist = Vector3.Distance(gameController.discoveredRessources[0].transform.position, transform.position);
int minDistIndex = 0;
for (int i = 1; i < gameController.discoveredRessources.Count; i++)
{
if (gameController.discoveredRessources[i].gameObject.CompareTag("Food"))
{
float dist = Vector3.Distance(gameController.discoveredRessources[i].transform.position, transform.position);
if (dist < minDist)
{
minDist = dist;
minDistIndex = i;
}
}
}
//Now you can move to gameController.discoveredRessources[minDistIndex]
Also you can store all the food/stones/wood in the separate lists when you find it

Answer 2

Using Linq Where and this usefull extension method MinBy
using System;
using System.Collections.Generic;
using System.Linq;
public static class Linqextensions
{
public static T MinBy<T, R>(this IEnumerable<T> en, Func<T, R> evaluate) where R : IComparable<R>
{
return en.Select(t => new Tuple<T, R>(t, evaluate(t)))
.Aggregate((max, next) => next.Item2.CompareTo(max.Item2) < 0 ? next : max).Item1;
}
}
(simply copy that code somwhere into your project) you could do it in "one" line
var closestItem = gameController.discoveredRessources
// this is a filter only selecting the ones with tag = "Food"
.Where(obj => obj.CompareTag("Food"))
// this returns you the item from the list with the lowest distance
.MinBy(obj => Vector3.Distance(obj.transform.position, transform.position));