Question

我正在更新数据库中的表，但它不断给我一个异常：NullReferenceException＆＃34;对象引用未设置为对象的实例。＆＃34;

我已将该片段粘贴下来：

for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
    double bal_due, a, b;
    a = double.Parse(dataGridView1.Rows[i].Cells[3].Value.ToString()); //this lines throws the exception
    b= double.Parse(dataGridView1.Rows[i].Cells[4].Value.ToString());
    bal_due = a - b;                        
    string var = string.Format(
        "update purchase_order set paid_today={0}, " + 
        "balance_due={1} where order_no={2}",
        dataGridView1.Rows[i].Cells[4].Value, bal_due, comboBox2.SelectedValue);
    obj.query(var);
}

Answer 1

我猜您正在尝试为datagridview底部的空行执行更新语句...将其添加到循环中：

for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
    if (dataGridView1.Rows[i].IsNewRow) continue;
    ...

在更新表时获取异常

1 个答案: