Need help on a calculator I'm making.

Question

I'm making a calculator that lets you choose what you want to do. 

Add, Subtract, Divide, or Multiply. and I'm running into a problem, I'm trying to make it so if the user presses the + button it will automatically clear the screen(Which I haven't added to the code) and ask for the numbers. 

The problem is it does not advance once the user chooses this.

Oh and also I'm a kind of new to C#. I'm not sure if the Convert.ToInt32's are necessary.

         static void Main(string[] args)
        

{
            

int Var1 = 0, Var2 = 0;

int userinput = 0;

Console.WriteLine("Addition (+), Subtraction (-), Division (/), or Multiplicaton (*)");

Console.ReadLine();

if (userinput == '+')
            

{
                

Console.WriteLine("Enter The First Number You Would Like To Add: ");

Var1 = Convert.ToInt32(Console.ReadLine());

Console.WriteLine("Enter The Second Number You Would Like To Add: ");

Var2 = Convert.ToInt32(Console.ReadLine());

Console.WriteLine("The Answer Is: ");

Console.WriteLine(Var1 + Var2);
            

}
        

}