我已经阅读了许多类似的问题并尝试了几种不同的方法,但我不明白为什么这不起作用。要求的列是int类型。我试过转换为uint和int32。我很欣赏方向。谢谢。
int i = 1;
int total=0;
while (i < 7)
{
string conString = @"Data Source=UATDB2\sqleuat;Initial Catalog=CVNee;User ID=appuser;Integrated Security=true";
SqlConnection connection = new SqlConnection(conString);
connection.Open();
SqlCommand cmd = connection.CreateCommand();
cmd.CommandText = "SELECT SUM(AMOUNT) FROM TRANSACTIONS_DETAIL2 WHERE TRANSACTIONS_DETAIL2.TRANS_TYPE =" + i + "AND TRANSACTIONS_DETAIL2.HOH_UPI = '185292000'";
int amt = ((int)cmd.ExecuteScalar());
//amt = cmd.ExecuteScalar();
if (i == 1)
{
total = total + amt;
}
if (i == 2)
{
total = total - amt;
}
if (i == 3)
{
total = total - amt;
}
if (i == 4)
{
total = total + amt;
}
if (i == 5)
{
total = total + amt;
}
if (i == 6)
{
total = total + amt;
}
connection.Close();
ViewBag.TotalBalance = total;
i++;
}
答案 0 :(得分:2)
当ExecuteScalar
返回null
时,会发生非法播放异常。您可以在转换为null
之前检查结果是否为int
,
object o = cmd.ExecuteScalar();
int result = o == null ? 0 : (int)o;
或者您可以使用可为空的int?
,如果它有值,也可以检查
int? result = (int?)cmd.ExecuteScalar();
if (!result.HasValue) result = 0;
或者您可以调整查询以返回0
,即使找不到匹配的行也是如此。 TSQL函数COALESCE
检查第一个参数是否为NULL
,否则返回该值,如果是,则返回第二个参数的值。
string query = "SELECT COALESCE(SUM(AMOUNT),0) FROM TRANSACTIONS_DETAIL2 WHERE TRANSACTIONS_DETAIL2.TRANS_TYPE =" + i + "AND TRANSACTIONS_DETAIL2.HOH_UPI = '185292000'";
答案 1 :(得分:1)
如果您致电ExecuteScalar
,可能会得到null
或DBNull
作为回报,您应该同时检查两者。您可以先将其填入object
类型的变量中,然后检查DBNull.Value
和null
并对此做出反应:
int amt=0;
object amtUnchecked = cmd.ExecuteScalar();
if(amtUnchecked != DBNull.Value && amtUnchecked!=null)
amt=(int)amtUnchecked;
或者您更改SELECT
以返回确定的零:SELECT ISNULL(SUM(AMOUNT),0) ...