<p>I'm working on a C# program, and right now I have one <code>Form</code> and a couple of classes. I would like to be able to access some of the <code>Form</code> controls (such as a <code>TextBox</code>) from my class. When I try to change the text in the <code>TextBox</code> from my class I get the following error:</p>

<blockquote>
  <p>An object reference is required for the non-static field, method, or property 'Project.Form1.txtLog'   </p>
</blockquote>

<p>How can I access methods and controls that are in <code>Form1.cs</code> from one of my classes?</p>

you have to have a reference to the form object in order to access its elements
the elements have to be declared public in order for another class to access them
don't do this - your class has to know too much about how your form is implemented; do not expose form controls outside of the form class
instead, make public properties on your form to get/set the values you are interested in
post more details of what you want and why, it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices