How to make string which contains datagridviews value

Question

Here Is my Code to check available data in table if there exist any one value of Gridviews Column it will return the available value. 
But there is somthing wrong so why it check only one value which is first in gridview.
The Code is as below
ok Here is the Full Code...
 
private void SureToDeleteBill() // Cheking For There Is No Imei in Bill Which Is Sold
{

try
{
for (int i = 0; i <= dataGridView2.Rows.Count-1; i++)
{
// check either imei is sold or available in Imei Sold table
cs.Open();
cmd = new OleDbCommand("select * from tblsIMEI where IMEI = @a0", cs);
cmd.Parameters.AddWithValue("@a0", dataGridView2.Rows[i].Cells[1].Value.ToString());
dr = cmd.ExecuteReader();
if (dr.Read())
{
string msg;
msg = dr["IMEI"].ToString();
MessageBox.Show("Sorry !!\nYou Can Not DeleteBill !\n Sold IMEI : ", "Sold IMEI", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
return;
}
else
{
DialogResult r = MessageBox.Show("Sure To Proceed?", "Delete Data", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (r == DialogResult.Yes)
{
DeleteFromtblPurchase();
DeleteFromtblIMEI();
DeleteFromPurchaseModel();
DeleteFromDealerBill();
MessageBox.Show("Record Delete Success!!", "Delete");
this.Close();
}
else
{
return;
}
}
cs.Close();
}
}

catch (Exception ex)
{
MessageBox.Show(ex.Message, "Sure To Delete");
}
finally
{
cs.Close();
}
}
Please help to solve it.