C#

public void test()
{
    _frm1.comboBox1.Items.Add("test");
}

public comboBox _comboBox1; 
public comboBox comboBox1; // the comboBox which is displaing
{
    get
    {
       return _comboBox1;
    }
    set
    {
       _comboBox1 = value;
    }
}
public void aaa()
{
    Class1 cls1 = new Class1();
    cls1.test();
}

public void test()
{
    Form1 frm1= new Form1();
    frm1.comboBox1.DataSource = new string[] {"aaa", "bbb"};
}

private void callFunctionFromForm()
{
    Class1 cls1 = new Class1(this); // <-- pass the form to cls1 through its constructor
    cls1.test();
}

public Class1(Form1 frm1) : this()
{
    _frm1 = frm1;
}

Form1 frm1= new Form1();
frm1.comboBox1.DataSource = new string[] {"aaa", "bbb"};

_frm1.comboBox1.DataSource = new string[] {"aaa", "bbb"};

frm1.comboBox1.DataSource = new string[] {"aaa", "bbb"};

...somewhere in Form1...
protected string[] _choices;
public string[] Choices
{
  get { return _choices; }
  set
  {
    _choices = value;
    comboBox1.DataSource = value;
  }
}

frm1.Choices = new string[] { "aaa", "bbb" };

class Form1
{
    private comboBox comboBox1; //its visible
    protected string _choices;
    public string[] Choices
    {
        get  {  return _choices;  }
        set
        {
            _choices = value;
            comboBox1.DataSource = value;
        }
    }
    public void someFunctionInForm1
    {
         Class1 cls1 = new Class1();
         cls1.test();
    }
}
class Class1
{
    public void test()
    {
        Form1 frm1 = new Form1();
        frm1.Choices = new string {"aaa", "bbb"}; // dont work
    }
}

...somewhere in Form1
Choices = new string[] {"ccc", "ddd"}; // Works

public void test()
{
    Form1 frm1 = new Form1(); // <--!
    frm1.Choices = new string {"aaa", "bbb"};
}

emran834 wrote:

Is that you meant My application will be running stand alone in the user's computer or The user must have SQL server installed !!

emran834 wrote:

Whenever i build my solution, the RELEASE Folder is Stand Alone and My .mdf file is inside the RELEASE Folder which made sense to me that it will run stand alone. Ain't I right ?