I apologize in advance with what will probably be a fairly easy/quick answer based on scope, but I\'ve looked everywhere and am surprised to not come up with an answer.
In your other class, create a method with objects as parameters.
public class TryMe (TextBox newTextbox) {
newTextbox.Text = "Hello this is a text."
//You can also get the value of textbox of another form
var textString = newTextbox.Text;
}
And then in your main form, call that method with your objects as parameters. In this case, add textbox1 to your method's parameter.
Your code in form:
TryMe(textbox1);