public class aDemoClass
{
    // Class Level Variables
    private System.Windows.Forms.DataGridView desiredDataGridView;

    public aDemoClass(System.Windows.Forms.Form form)
    {
        DataGridView addANewDatagridview = new DataGridView();
        form.Controls.Add(addANewDatagridview);
        desiredDataGridView = addANewDatagridview;
    }

}

public partial class MainForm : Form
{
    aDemoClass newObj;
    aDemoClass  newObj2;

    public MainForm()
    {
        InitializeComponent();
        newObj = new aDemoClass(this);
        newObj2 = new aDemoClass(this);
    }
}