将varchar转换为数值数据类型的算术溢出错误。 尝试从数据库读取时并非每次都会发生

Question

I'm trying to read in from a local database and create and return an object. my code works fine the first 3 times through the loop that calls it and then fails giving me an error: Arithmetic overflow error converting varchar to data type numeric. I've done plenty of debugging and the error is being thrown at reader.Read(). To my knowledge I'm not converting anything there, and all my research has turned up completely different sources for this error. any help would be greatly appreciated.

System.Data.SqlClient.SqlDataReader reader;
/*Initialize Variables*/
        using (SqlCommand cmd = GetCommand("SELECT * FROM tblInventoryItem where InvoiceID = " + InvoiceNumber))
        {
            //Do Work...
            try
            {
                cmd.Connection.Open();
                reader = cmd.ExecuteReader();

                InventoryItem i;
                NItem ni;
                InventoryDataRepository2 idr = new InventoryDataRepository2();

                while (reader.Read())
                {
                    //Create an instance of the object....
                    i = new InventoryItem();
                    ni = new NItem();

                    ni.ItemNumber = (string)reader["ItemNumber"];
                    InventoryItem invitem = (InventoryItem)idr.GetItem(ni.ItemNumber);
                    ni.Title = invitem.Item.Title;
                    ni.Model = invitem.Item.Model;
                    ni.RetailPrice = invitem.Item.RetailPrice;
                    ni.WholesalePrice = invitem.Item.WholesalePrice;
                    i.Item = ni;
                    i.Quantity = Convert.ToInt32(reader["Quantity"]);


                    allItems.Add(i);
                }

EDIT: stacktrace:

 at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
 at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
 at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
 at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
 at System.Data.SqlClient.SqlDataReader.TryHasMoreRows(Boolean& moreRows)
 at System.Data.SqlClient.SqlDataReader.TryReadInternal(Boolean setTimeout, Boolean& more)
 at System.Data.SqlClient.SqlDataReader.Read()
 at NeweggDistributor.InventoryItemDataRepository.GetAllItemsInInvoice(String InvoiceNumber) in c:\Users\AJ\Documents\Visual Studio 2012\Projects\NeweggDistributor\NeweggDistributor\InventoryItemDataRepository.cs:line 90
 Arithmetic overflow error converting varchar to data type numeric.

Answer 1

I agree with Eric J. i don't believe Reader.Read() would throw such an error. What i see is likely to throw such an error tho is if the Quantity field in the DB is a string and cannot be converted to an integer, or if it is null in the DB because null cannot be converted to any integer. other possibilities are the RetailPrice and WholesalePrice fields. Perhaps you can comment out those lines and make sure you don't get the same error when they are commented out. then you can uncomment each field one at a time, testing that each field one new field at a time.

My first guess is that i.Quantity = Convert.ToInt32(reader["Quantity"]); is trying to convert a varchar field into an int and the varchar string is not numeric. I hardly ever use Convert.ToInt32 or C# casting for situations like this because they can throw unexpected nasty errors. I create a separate method that converts what i want, and i pass it a default value that is returned if the conversion cannot be performed. Thus i use a 'defaultValue' parameter in my conversion methods.

Answer 2

Your query is

SELECT * 
FROM tblInventoryItem 
WHERE InvoiceID = 1234

My guess is that InvoiceID in the database is a varchar field. This means that you are comparing an integer with a varchar in the where clause. Implicit conversions changes your query to

SELECT * 
FROM tblInventoryItem 
WHERE CONVERT(int, InvoiceID) = 1234

You will get an error if any InvoiceID in the database contains something which will not fit into an integer.

The arithmetic overflow error make the most probable cause an invoiceid > 2147483648

Note that the error will not happen if your InvoiceNumber is also to big for an integer.

SELECT * 
FROM tblInventoryItem 
WHERE InvoiceID = 5000000000

will work because it is changed to

SELECT * 
FROM tblInventoryItem 
WHERE CONVERT(bigint, InvoiceID) = 5000000000

The solution is of course to use parameters

command.CommandText = @"SELECT * " +
                      @"FROM tblInventoryItem " +
                      @"WHERE InvoiceID = @InvoiceNumber";
command.Parameters.Add("@InvoiceNumber", SqlDbType.VarChar).Value = InvoiceNumber;

(You can also use a parameter of type SqlDbtype.BigInt if you are sure InvoiceID only contain numbers)