c＃数组-索引超出范围异常

Question

I am getting indexoutofrangeexception (see ----> pointer for the line generating the error down below in the code). The program loops through the header and line item records in a dataset tables. The tables have a relationship. My sample data has 2 headers, each with 2 lines. The progam has two loops, the first one loops through the header records and the second one loops through the child records of the header.

Part of the program:

     // ***** PO Header and Line 

        int ln;
        ln = 0;

        // Create an eConnect PO Header node object
        taGLTransactionHeaderInsert jeh = new taGLTransactionHeaderInsert();

        // Create an array for lineitems
        taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[] lineitems = new   taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[ln];

        foreach (DataRow dtrHDR in ds.Tables["Header"].Rows)

        {
            Array.Clear(lineitems, 0, ln);

            jeh.BACHNUMB = "Sheraz";
            jeh.JRNENTRY = jenoint;
            jeh.REFRENCE = dtrHDR["Reference"].ToString();
            jeh.SOURCDOC = dtrHDR["AvantisJE"].ToString();
            jeh.USERID = System.Environment.UserName;
            jeh.TRXDATE = System.DateTime.Now.ToString();

            ln = 0;

            foreach (DataRow dtrLine in dtrHDR.GetChildRows("HdrLine"))

            {

                // Populate the elements of the taPoLIne_ItemsTaPOLine XML node
                taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert jel = new taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert();

                jel.BACHNUMB = jeh.BACHNUMB;
                jel.JRNENTRY = jeh.JRNENTRY;
                jel.ACTNUMST = dtrLine["GreatPlains"].ToString();
                jel.DEBITAMT = Convert.ToDecimal(dtrLine["Debit"].ToString());

                //Avantis Inv Trx Key
                jel.ORDOCNUM = dtrLine["AvantisJE_Line"].ToString();
                // Avantis GL Trx Type
                jel.ORTRXDESC = dtrLine["transactiontypename"].ToString();


                //Add POLine to an Array
                lineitems[ln] = jel;     ----------------> I get an error here!

                ln = ln + 1;

                Array.Resize(ref lineitems, ln + 1);

            }

        }

Answer 1

This is because you created an array with 0 elements and try to insert an element on position 0. This will not work. You can fix it by declaring the array with a size of 1 to begin with:

// Create an array for lineitems
taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[] lineitems = new   taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[1];

However, resizing an array on the fly is not the idiomatic .NET way of doing this. You could use a List<T> , which takes care of resizing for you, and leaving you with cleaner code and possibly better performance.

Answer 2

You are accessing an index that doesn't yet exist.

//Add POLine to an Array
lineitems[ln] = jel;     ----------------> I get an error here!
ln = ln + 1;     
Array.Resize(ref lineitems, ln + 1);

You need to change the order to :

//Add POLine to an Array
Array.Resize(ref lineitems, ln + 1);
lineitems[ln] = jel;     ----------------> should be fixed, no error here!
ln = ln + 1;     

EDIT: Now that the immediate problem is out of the way, on to a better implementation.

Arrays are of a fixed sized, resizing an array is an expensive operation (basically it entails creating a copy with a new size). typically you would use these after identifying a performance bottle neck. In most cases it would be much better to use a List.

I'd recommend changing this line:

// Create an array for lineitems
taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[] lineitems = 
              new    taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[ln];

to:

var lineitems = new  List<taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert>();

and then to add to it you simply do

lineitems.Add(jel);

to iterate over them would be:

for (var ln in lineitems) {
 // whatever you want to do with a line.
}

to acccess a specific item by index would be:

lineitems.Item(i); // get the ith item in the list.

Answer 3

It appears that you're trying to increase the size of the array by setting a value, like you might do in JavaScript. C# arrays are not like that. You need to create them at the size you want them to be when finished.

Alternately, you could use a List object, using the Add() method to put new content into the list.

Answer 4

lineitems is obviously not the same size as the row collection returned by dtrHDR.GetChildRows("HdrLine") . You are creating an array of zero elements and then trying to index into it. If you want it to match the size of dtrHDR.GetChildRows("HdrLine") then you need to call that first and initialize the array after you can get the count.

Instead of using an array why don't you use a List<T> and just push items onto it? No need to worry about IndexOutOfRange exceptions anymore.

Answer 5

You need to initialize the array before putting anything in to it. call the .resize first.

Answer 6

those lines are the problem

 int ln;
 ln = 0;

 // Create an array for lineitems
 taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[] lineitems = new   taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[ln];

You create table of 0 elements.

Answer 7

You have an off-by-one error in your program:

    int ln = 0
    .
    .
    .
    taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[] lineitems = new   taGLTransactionLineInsert_ItemsTaGLTransactionLineInsert[ln];
    .
    .
    .
    lineitems[ln] = jel;

You are initializing an array of 0 elements, then trying to set the first element (element[0]) to a value.