Get missed element in integer collection, C#

Get missed element in integer collection

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Data;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var n = 10;
            var coll = new int[n];
            for(var i = 0; i < n; i++){coll[i]=i+1;}
            
            coll[5] = 3;
            
            
            Console.WriteLine(GetMissedUnsorted(coll));
            //Array.Sort(coll);
            Console.WriteLine(GetMissedUnsorted2(coll));
        }
        
        public static int GetMissedUnsorted(int[] coll){
            var n = coll.Length;
            var missed = -1;
            
            var sum = (n * (n+1)) / 2;
            var sumOrigin = 0;
            
            //Your code goes here
            foreach(var i in coll.Distinct()){
                sumOrigin += i;
            }
            
            return sum - sumOrigin;
        }
        
        public static int GetMissedSortedDirrect(int[] coll){
            //Your code goes here
            var result = 0;
            foreach(var i in coll){
                if(result == i) return i+1;
                result = i;
            }
            
            return result;
        }
        
        public static int GetMissedUnsorted2(int[] coll){
            //Your code goes here

for(var i = 0; i < coll.Length; i++){
                if(coll[i]!=i + 1) return i + 1;
            }
            
            throw new Exception("The missed element not found!");
        }
    }
}


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