Question

我尝试将SQL Results保存在数组中并将其返回。但我得到一个例外：数组超出范围错误。

这是我的代码：

 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;
}

我缺少什么？

Answer 1

bookingupdate = new BookingUpdate[c];
bookingupdate[c].bookingID = (long)rdr["ID"];

您正在创建一个长度为c的数组，这意味着它具有索引0 to (c-1) - 然后当您尝试存储在位置c时，您将超出范围。

Answer 2

Imho我将使用Linq简化你构建该数组的方法：

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();

通过这种方式，您不会遇到超出界限的数组问题。

Answer 3

您似乎正在使用

为数组创建和分配内存

bookingupdate = new BookingUpdate[c];

但实际上并没有创建BookingUpdate的实例。当您尝试在数组元素上设置属性时，没有实际的BookingUpdate要更新 - 只有一个持有者。

我建议将代码改为：

...
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"];
    ...

我希望这有帮助！

Answer 4

您访问超出范围的n元素数组的第n个元素，您需要访问n - 1元素。

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

数组的零基于索引。

当您创建bookingupdate = new BookingUpdate[c];时，您的上一个索引会c-1。

您无法访问BookingUpdate[c]，因为它不是存在。

让我们说c = 4，这意味着我们定义了一个包含4个元素的数组;

BookingUpdate[0]
BookingUpdate[1]
BookingUpdate[2]
BookingUpdate[3]

BookingUpdate[c]等于BookingUpdate[4]，没有这样的索引。

来自MSDN页;

数组是零索引的：具有 n 元素的数组从 0 索引到的 N-1

Answer 6

问题与数组的大小有关;

 for (int c = 0; c < count; c++)
 {
    bookingupdate = new BookingUpdate[c];
    bookingupdate[c].bookingID = (long)rdr["ID"];

在前面的代码中，您首先要创建一个大小为0的数组（bookingupdate）;然后你试图插入一个项目。即使你以某种方式设法跳过第一个，它也会再次失败。只需将这些行更新为以下内容;

bookingupdate = new BookingUpdate[count];
for (int c = 0; c < count; c++)
     {        
        bookingupdate[c].bookingID = (long)rdr["ID"];

Answer 7

            for (int c = 0; c < count; c++)
            {
                bookingupdate = new BookingUpdate[c];

错误是此for循环的第一次迭代，其中c为零。即，您正在尝试创建一个长度为零的数组。 bookingupdate = new BookingUpdate [0];

Answer 8

在调用之前，您已经初始化了一个数组，但不是该类本身。你的初始化也是错误的

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 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;

}

索引数组超出范围异常

9 个答案: