我尝试保存一个数组中的SQL结果，然后返回。 但我发现了异常：数组超出范围的错误。
这里是我的代码：
public BookingUpdate[] getBookingUpdates(string token)
{
String command = "SELECT b.ID,b.VERANSTALTER, rr.VON ,rr.BIS, b.THEMA, b.STORNO, ra.BEZEICHNUNG from BUCHUNG b JOIN RESERVIERUNGRAUM rr on rr.BUCHUNG_ID = b.ID JOIN RAUM ra on ra.ID = rr.RAUM_ID WHERE b.UPDATE_DATE BETWEEN DATEADD (DAY , -20 , getdate()) AND getdate() AND b.BOOKVERNR = 0";
SqlConnection connection = new SqlConnection(GetConnectionString());
BookingUpdate[] bookingupdate = new BookingUpdate[1];
connection.Open();
try
{
SqlCommand cmd = new SqlCommand(command, connection);
SqlDataReader rdr = null;
int count = 0;
rdr = cmd.ExecuteReader();
while (rdr.Read())
{
DataTable dt = new DataTable();
dt.Load(rdr);
count = dt.Rows.Count;
for (int c = 0; c < count; c++)
{
bookingupdate = new BookingUpdate[c];
bookingupdate[c].bookingID = (long)rdr["ID"]; // <---- Error is here
bookingupdate[c].fullUserName = rdr["VERANSTALTER"].ToString();
bookingupdate[c].newStart = (DateTime)rdr["VON"];
bookingupdate[c].newStart = (DateTime)rdr["BIS"];
bookingupdate[c].newSubject = rdr["THEMA"].ToString();
bookingupdate[c].newlocation = rdr["BEZEICHNUNG"].ToString();
if (rdr["STORNO"].ToString() != null)
{
bookingupdate[c].deleted = true;
}
else
{
bookingupdate[c].deleted = false;
}
}
}
}
catch (Exception ex)
{
log.Error(ex.Message + "\n\rStackTrace:\n\r" + ex.StackTrace);
}
finally
{
connection.Close();
}
return bookingupdate;
}
我在想什么？
Answer 1:
你似乎是创建和使用数组分配内存
bookingupdate = new BookingUpdate[c];
但实际上没有创造BookingUpdate的实例。 当您尝试您的数组元素上设置的属性没有实际BookingUpdate更新 - 只有一个持有人。
我建议改变你的代码的线沿线的东西：
...
bookingupdate = new BookingUpdate[count]; // allocates space for the number of BookingUpdates to be created
for (int c = 0; c < count; c++)
{
bookingupdate[c] = new BookingUpdate(); // create a new instance of BookingUpdate and assign it the array
bookingupdate[c].bookingID = (long)rdr["ID"];
...
我希望这个对你有用！
Answer 2:
bookingupdate = new BookingUpdate[c];
bookingupdate[c].bookingID = (long)rdr["ID"];
要创建长度的数组c ，这意味着它具有索引0 to (c-1) -然后你超出边界，试图在位置来存储时c 。
Answer 3:
恕我直言，我将简化你的方式来构建阵列使用LINQ：
BookingUpdate[] bookingupdate = dt.AsEnumerable()
.Select(r => new BookingUpdate{
bookingID = r.Field<long>("ID"),
fullUserName = r.Field<string>("VERANSTALTER"),
newStart = r.Field<DateTime>("Von"),
newEnd = r.Field<DateTime>("Bis"), // here was another bug in your originalcode
newSubject = r.Field<string>("THEMA"),
newlocation = r.Field<string>("BEZEICHNUNG"),
deleted = r.Field<string>("STORNO") != null
})
.ToArray();
在这条路上，你不会有界限以外的阵列问题。
Answer 4:
您访问的n个元素的数组这是超出范围的第n个元素，你需要访问N - 1元。
bookingupdate = new BookingUpdate[c]; // You create an array of 5 elements for example
bookingupdate[c].bookingID = (long)rdr["ID"]; // Here you access the 5th elements but there are only 4
Answer 5:
该问题与阵列的尺寸相关;
for (int c = 0; c < count; c++)
{
bookingupdate = new BookingUpdate[c];
bookingupdate[c].bookingID = (long)rdr["ID"];
在前面的代码，要创建的阵列（ bookingupdate在第一大小0）; 那么你要插入一个项目。 即使你以某种方式设法跳过第一个，它会再次失败。 只要更新这些线以下;
bookingupdate = new BookingUpdate[count];
for (int c = 0; c < count; c++)
{
bookingupdate[c].bookingID = (long)rdr["ID"];
Answer 6:
for (int c = 0; c < count; c++)
{
bookingupdate = new BookingUpdate[c];
错误是在for循环，其中c为0的这个第一次迭代。 也就是说，你要创建长度为零的数组。 bookingupdate =新BookingUpdate [0];
Answer 7:
你已经初始化数组而不是类本身调用它。 此外，您的初始化是错误的
count = dt.Rows.Count;
bookingupdate = new BookingUpdate[count];
for (int c = 0; c < count; c++)
{
bu = new BookingUpdate();
bu.bookingID = (long)rdr["ID"]; // <---- Error is here
bu.fullUserName = rdr["VERANSTALTER"].ToString();
bu.newStart = (DateTime)rdr["VON"];
bu.newStart = (DateTime)rdr["BIS"];
bu.newSubject = rdr["THEMA"].ToString();
bu.newlocation = rdr["BEZEICHNUNG"].ToString();
if (rdr["STORNO"].ToString() != null)
{
bu.deleted = true;
}
else
{
bu.deleted = false;
}
bookingupdate[c] = bu;
}
Answer 8:
阵列具有从零开始的索引 。
当您创建bookingupdate = new BookingUpdate[c]; 你最后的指数将c-1
您不能访问BookingUpdate[c]因为不存在 。
比方说， c = 4 ，这意味着我们具有4个元件其中它们definedan阵列;
BookingUpdate[0]
BookingUpdate[1]
BookingUpdate[2]
BookingUpdate[3]
BookingUpdate[c]将等于BookingUpdate[4]其中不存在这样的索引。
从MSDN页面;
阵列零索引：与n个元素的数组是从0索引到N-1。
Answer 9:
使用此代码。
public BookingUpdate[] getBookingUpdates(string token)
{
String command = "SELECT b.ID,b.VERANSTALTER, rr.VON ,rr.BIS, b.THEMA, b.STORNO, ra.BEZEICHNUNG from BUCHUNG b JOIN RESERVIERUNGRAUM rr on rr.BUCHUNG_ID = b.ID JOIN RAUM ra on ra.ID = rr.RAUM_ID WHERE b.UPDATE_DATE BETWEEN DATEADD (DAY , -20 , getdate()) AND getdate() AND b.BOOKVERNR = 0";
BookingUpdate[] bookingupdate;
SqlConnection connection = new SqlConnection(GetConnectionString());
connection.Open();
try
{
SqlCommand cmd = new SqlCommand(command, connection);
SqlDataReader rdr = null;
int count = 0;
rdr = cmd.ExecuteReader();
while (rdr.Read())
{
DataTable dt = new DataTable();
dt.Load(rdr);
count = dt.Rows.Count;
bookingupdate = new BookingUpdate[count];
for (int c = 0; c < count; c++)
{
bookingupdate[c].bookingID = (long)rdr["ID"]; // <---- Error is here
bookingupdate[c].fullUserName = rdr["VERANSTALTER"].ToString();
bookingupdate[c].newStart = (DateTime)rdr["VON"];
bookingupdate[c].newStart = (DateTime)rdr["BIS"];
bookingupdate[c].newSubject = rdr["THEMA"].ToString();
bookingupdate[c].newlocation = rdr["BEZEICHNUNG"].ToString();
if (rdr["STORNO"].ToString() != null)
{
bookingupdate[c].deleted = true;
}
else
{
bookingupdate[c].deleted = false;
}
}
}
}
catch (Exception ex)
{
log.Error(ex.Message + "\n\rStackTrace:\n\r" + ex.StackTrace);
}
finally
{
connection.Close();
}
return bookingupdate;
}
文章来源: indexing Array out of Range Exception
