The type HashSet could not be found

Question

in Visual Studio 2013 I typed this program:
using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication5
{
class Program
{
static void Main(string[] args)
{
HashSet<int> hs = new HashSet<int>();
for (int x=1; x<=5; x++){
hs.Add(x);
}
Console.Write(hs.Count);
}
}
}
but it can not run in VS and error is The type HashSet could not be found.
while it can be run in SoloLearn platform.
How Can I solve this on my VisualStudio?

Answer 1

What is the .net framework you target.

HashSet only starts from .net framework 3.5.

You can find it in the menu -> project -> ConsoleApplication5 Properties

Answer 2

Thanks. I find out that the target framework was on .net 3 . I set that on .net framework 3.5 and it works

Answer 3

Well done.