Referencing non-static fields from static function

Question

I want to programmatically determine the space I've got for some controls I want to create dynamically. So, I want to get the container's height and divide it by the number of rows (a constant).

I've got this function (this code is part of the form on which the panel named dynamicPanel lives):

private static int getControlHeightToUse() {
  return (dynamicPanel.Height / NUMBER_OF_ROWS);
}

...which gives me the compile-time error, "*An object reference is required for the non-static field, method, or property RememberNextGen_CRLogins.CRLoginsMainForm.dynamicPanel'*"

I don't understand what it's trying to tell me/what it wants.

If I remove the "static":

private int getControlHeightToUse() {
  return (dynamicPanel.Height / NUMBER_OF_ROWS);
}

...I then get the compile-time error, "*A field initializer cannot reference the non-static field, method, or property 'TitanNextGen_CRLogins.CRLoginsMainForm.getControlHeightToUse()'*"

...on the indicated line below:

public partial class CRLoginsMainForm : Form {

  int controlHeight = getControlHeightToUse(); // <-- err

Answer 1

pass dynamicPanel as parameter to static method

public partial class CRLoginsMainForm : Form {

  int controlHeight = getControlHeightToUse(dynamicPanel);

change getControlHeightToUse as below

private static int getControlHeightToUse(Panel panel) {
  return (panel.Height / NUMBER_OF_ROWS);
}

if you want to call non static method from static method you can do as below

public class Foo
{
    // public method 
    public void Method1()
    {
    }

    public static void Data2()
    {
        // call public method from static method
        new Foo().Method1();

    }
}

Answer 2

A static method has only direct access to static memebers of the class, if you want to use instance members of the class, you must pass in an instance of the class to the method (or have one available as a static as in the case of a singleton).

Thus, you can modify your method to take in the instance member that is preventing it from being able to be static:

private static int getControlHeightToUse(Panel thePanel) 
{
  return (thePanel.Height / NUMBER_OF_ROWS);
}

Then just pass in dynamicPanel on the call...

Instance methods, however, can access static members. Remember that static members are shared among all instances and exist even if no instance of the class exist. Thus they can't call instance members since they don't know which instance you are talking about.