索引数组超出范围异常

Question

我尝试将SQL结果保存在数组中并将其返回。但我收到一个异常：数组超出范围错误。

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; 
} 

我失去了什么？

Answer 1

你似乎是创建和使用

bookingupdate = new BookingUpdate[c]; 

为数组分配内存，但实际上并不产生BookingUpdate实例。当您尝试在数组元素上设置属性时，没有实际的更新预订更新 - 只有一个持有者。

我建议沿着线改变你的代码的东西：

... 
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"]; 
    ... 

我希望这有助于！

Answer 2

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

要创建长度c的数组，这意味着它有指标0 to (c-1) - 然后你是出界，试图在位置c存储时。

Answer 3

您正在访问超出范围的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 4

阵列具有从零开始的索引。

当您创建bookingupdate = new BookingUpdate[c];时，您的最后一个索引将为c-1。由于不是存在。

比方说c = 4，这意味着我们定义一个数组，它包含4个元素;

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;

数组是零索引：与Ñ元素的数组是从0 索引到 n-1个。

Answer 5

该问题与数组大小有关;

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

在前面的代码

，要创建在第一大小为0的数组（bookingupdate）;那么你正试图插入一个项目。即使你设法跳过第一个，它也会失败。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 6

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

错误是在for循环，其中c是零的这种第一次迭代。即，您正尝试创建一个长度为零的数组。 bookingupdate = new BookingUpdate [0];

Answer 7

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 8

在调用它之前，您已经初始化了一个数组，但不是该类本身。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 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; 

}