Deja Vu solution not quite working

Question

I know there are other ways, but is this a viable way to solve the Deja Vu code coach problem? It currently isn't working.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
string input = Console.ReadLine();

string modInput = null;

bool dejaBool = false;

foreach (char c in input )
{
char tempChar = c;

modInput = input.Remove(input.IndexOf(c));

if (modInput.Contains(tempChar))
{
dejaBool = true;
}

}
if (dejaBool ==true) Console.WriteLine("Deja Vu");
else {Console.WriteLine ("Unique");}
}
}
}

Answer 1

That did it. Thank you!

Answer 2

#hope it helps
#python

str1=input("")
count={}
str2=[2,3,4,5,6,7,8,9]
for i in str1:
if i in count:
count[i]+=1
else:
count[i]=1
val=count.values()
set1=set(count.values())

if set1=={1}:
print("Unique")
else:
for s in str2:
if s in val:
print("Deja Vu")