System.Text.StringBuilder.ToString C# (CSharp) Method

		public string ToString (int startIndex, int length) 
		{
			// re-ordered to avoid possible integer overflow
			if (startIndex < 0 || length < 0 || startIndex > _length - length)
				throw new ArgumentOutOfRangeException();

			// use String.SubstringUnchecked instead of String.Substring
			// as the former is guaranteed to create a new string object
			if (startIndex == 0 && length == _length)
				return ToString ();
			else
				return _str.SubstringUnchecked (startIndex, length);
		}

        public static EditProblemViewModel GetEditProblemViewModel(Problem problem)
        {
            var epvm = new EditProblemViewModel();
            epvm.Author = problem.Author.UserName;
            epvm.Name = problem.Name;
            epvm.Text = problem.Text;
            epvm.SelectedCategoryId = problem.CategoryId;
            epvm.IsBlocked = problem.IsBlocked;

            var sb = new StringBuilder();
            foreach (var tag in problem.Tags)
            {
                sb.Append(tag.Name);
                sb.Append(',');
            }

            epvm.TagsString = sb.ToString();

            sb.Clear();

            foreach (var ans in problem.CorrectAnswers)
            {
                sb.Append(ans.Text);
                sb.Append(';');
            }

            sb.Remove(sb.Length - 1, 1);
            epvm.Answers = sb.ToString();

            return epvm;
        }