datagridview data transfer from one form to other form

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.NET3.5

C#

.NET

i am using 2 forms having both of them having separate datagrid. i
did't bound any datagrid to any datasource but i just added some rows to one datagrid and want to copy it to other form datagrid using the code

RegistrationForm rg = new RegistrationForm(); 
for (int i = 0; i < this.dataGridView2.Rows.Count-1; i++)  
 {    
string[] values = { this.dataGridView2.Rows[i].Cells  ["TestID"].Value.ToString(), this.dataGridView2.Rows[i].Cells["TestName"].Value.ToString(), this.dataGridView2.Rows[i].Cells["Charges"].Value.ToString(), this.dataGridView2.Rows[i].Cells["DeliveryDate"].Value.ToString() ;
}
 rg .dataGridView1.Rows.Add(values);//dataGridView is on an other form
his.Close();

this code shows in debuger that the data is copied but in the datagrid it not displys.
why ?
any sugistion or any alternate code pleas.