Changing values of another form from a separate form (solution not working)

Question

peoples. Today I\'m attempting to change the background image of a panel from a separate form. I\'ve looked at a few S.O. questions and they have all said to create a new form

Answer 1

You have to change the variable in the specific instance of the form that you want to change. I would recommend adding the form as a parameter of your method or convert your static method to an extension method.

Parameter:

public static void changeGridSize(Form_Main frm, int newSize)
{
    switch (newSize) 

Extension Method:

public static void changeGridSize(this Form_Main frm, int newSize)
{
    switch (newSize)

Usage of the extension method would be from the calling form:

myFormMain.changeGridSize(newSize);

Answer 2

Your "other" form needs an instance of the main form (Form_Main), which you have stored as a variable named frm. With this variable you can call the main form instance, like this:

frm.changeGridSize(newSize);

Instead you are trying to call the form like it is a static class by using the syntax:

Form_Main.changeGridSize(newSize);

To get the instance of the main form to the "other" form, you can pass it to the constructor of the other form, like this:

public class OtherForm : Form
{
    Main_Form _mainForm;

    // Constructor
    public OtherForm(Main_Form theMainForm)
    {
        _mainForm = theMainForm;
    }

    public static void changeGridSize(int newSize)
    {
        _mainForm.changeGridSize(newSize);
    }
}

Finally, when you are creating your "other" form, you will need to pass an instance of the main form, like this:

OtherForm theOtherForm = new OtherForm(this);