CS0120: An object reference is required for the nonstatic field, method, or property 'foo'

Question

Consider:

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            


        

Answer 1

From my looking you give a null value to a textbox and return in a ToString() as it is a static method. You can replace it with Convert.ToString() that can enable null value.