Why can't you call a non-static method from a static method?

Question

I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error:

Answer 1

First you need to create instance of the class in order to call non-static method or functions.

public class ClassHelper()
{
   public static ClassHelper GetInstance()
    {
        ClassHelper instance = null;

        if (System.Web.HttpContext.Current == null)
        {
            instance = new ClassHelper();
            return instance;
        }

        if (System.Web.HttpContext.Current.Application["CLASSHELPER_INSTANCE"] == null)
        {
            instance = new ClassHelper();
            System.Web.HttpContext.Current.Application["CLASSHELPER_INSTANCE"] = instance;
        }

        instance = (ClassHelper)System.Web.HttpContext.Current.Application["CLASSHELPER_INSTANCE"];

        return instance;
    }


   public string Test()
   {
       return "test123";
   }

}

Then you can call the function as follows:

textBox1.Text = ClassHelper.GetInstance().Test();