ต้องการที่จะเพิ่มค่าเข้าไป DataGridView หากเป็นค่าที่ซ้ำกัน ให้บวกเพิ่มเข้าไป

			Dim objConn As New SqlConnection
			Dim objCmd As New SqlCommand
			Dim strConnString,strSQL As String
			strConnString = "Server=localhost;UID=sa;PASSWORD=;database=mydatabase;Max Pool Size=400;Connect Timeout=600;"
			objConn.ConnectionString = strConnString
			objConn.Open()

			Dim intNumRows As Integer
			strSQL = "SELECT COUNT(*) FROM customer WHERE CustomerID = '"& Me.txtCustomerID.Text &"' "		
			objCmd = New SqlCommand(strSQL, objConn)
			intNumRows = objCmd.ExecuteScalar()

			IF intNumRows > 0 Then

				strSQL = "UPDATE ..... "

				objCmd = New SqlCommand
				With objCmd
				   .Connection = objConn
				   .CommandText = strSQL
				   .CommandType = CommandType.Text		   
				End With
								
				objCmd.ExecuteNonQuery()
			Else	
			

				strSQL = "INSERT ..... "

				objCmd = New SqlCommand
				With objCmd
				   .Connection = objConn
				   .CommandText = strSQL
				   .CommandType = CommandType.Text		   
				End With
								
				objCmd.ExecuteNonQuery()

		End IF

		objConn.Close()
		objConn = Nothing

var dgv = from dgvr in dataGridView1.Rows.Cast<DataGridViewRow>()
where (string)dgvr.Cells[0].Value == textBoxCode.Text
select dgvr;

if (dgv.Count() > 0)
{
(from dgvr in dataGridView1.Rows.Cast<DataGridViewRow>()
where (string)dgvr.Cells[0].Value == textBoxCode.Text
select dgvr).ToList().ForEach(dgvr =>
{
dgvr.Cells[1].Value += Convert.ToInt32(textBoxAmount.Text);
dgvr.Cells[2].Value += Convert.ToInt32(textBoxAmount.Text) * Convert.ToInt32(textBoxPrice.Text);
})
}
else
{
dataGridView1.Rows.Add(textBoxCode.Text, Convert.ToInt32(textBoxAmount.Text), Convert.ToInt32(textBoxAmount.Text) *  Convert.ToInt32(textBoxPrice.Text));
}