C# nullable string error

Question

private string? typeOfContract
{
  get { return (string?)ViewState[\"typeOfContract\"]; }
  set { ViewState[\"typeOfContract\"] = value; }
}

Later

Answer 1

string cannot be the parameter to Nullable because string is not a value type. String is a reference type.

string s = null; 

is a very valid statement and there is not need to make it nullable.

private string typeOfContract
    {
      get { return ViewState["typeOfContract"] as string; }
      set { ViewState["typeOfContract"] = value; }
    }

should work because of the as keyword.