Question

SqlConnection con = new SqlConnection(@"Data Source=DESKTOP-IBPJNA2;Initial Catalog=GeometryFINAL;Integrated Security=True");
SqlCommand cmd;
SqlDataReader rdr;         
int intOrderNo = (int)Session["sOrderNo"]; //error is here
String strSql = "SELECT iProductID FROM orderItemsTable WHERE iOrderNo = " + intOrderNo;
cmd = new SqlCommand(strSql, con);

Answer 1

确保您的Session["sOrderNo"]上有值。看起来它不存在或者值不能转换为整数。

你能做的是：

SqlConnection con = new SqlConnection(@"Data Source=DESKTOP-IBPJNA2;Initial Catalog=GeometryFINAL;Integrated Security=True");
SqlCommand cmd;
SqlDataReader rdr;
if (Session["sOrderNo"] != null)
{
   int intOrderNo = 0;
   bool result = Int32.TryParse(Session["sOrderNo"], out intOrderNo );
   if (result)
   {
      String strSql = "SELECT iProductID FROM orderItemsTable WHERE iOrderNo = " + intOrderNo;
      cmd = new SqlCommand(strSql, con);  
   }
   else
   {
       //values are not convertable to integer....
   }
}
else
{
   //your session variable doesn't exist....
}

Answer 2

会话[＆＃34; sOrderNo＆＃34;]在您设置时不存在或不是int类型

您需要先检查

int intOrderNo = 0;
if(Session["sOrderNo"]!=null)
{
  int.TryPasre(Session["sOrderNo"].ToString(), out intOrderNo); 
}

Answer 3

在将会话值分配给变量orderno时，可能存在两种可能的情况

Session["sOrderNo"]尚未初始化
Session["sOrderNo"]不包含任何值。

所以为了处理这两种情况，最好的方法是

int intOrderNo = 0;
if(Session["sOrderNo"]!=null)
{
  intOrderNo = Convert.ToInt32(Session["sOrderNo"]); 
}

错误：指定的强制转换无效（Asp net，c＃，SQL）

3 个答案: