C#

public void btnClick(object sender, EventArgs e)
{
   showForm(formObject);
}

public void showForm(Form myForm)
{
   myForm.Show();
}

void showForm( Iobject obj)
{
}

public void button_click(..)
{
    showForm(new formObject());
}

void ShowForm(Type formType)
{
    Form frm = Activator.CreateInstance(formType) as Form; // your type must be some kind of form
    if (frm != null)
    {
        frm.Show(); // showing the form
    }
    else
    {
        // formType is not a form, handle the error
    }
}

void PassButton(Button myButton)
{
   //Do stuff with myButton
}

void PassForm(Form myForm)
{
   //Do stuff with myForm
   //Form is the class from which your own for is derived, you can cast it to
   //any form you want or use your selfmade Form (like F_Main)
}