ASMX Service Doesn't Always Return Data

Question

I am working with an ASMX service in ASP.NET/C#. My service returns proper data for some of my WebMethods, but not all. The interesting part is all of the WebMethods are very similar.

Here's one that always returns data:

[WebMethod]
public AccountItem[] GetAllAccounts()
{
    AccountItem[] AccountItems = HttpContext.Current.Cache[AccountItemsCacheKey] as AccountItem[];
    if (AccountItems == null)
    {
        List<AccountItem> items = new List<AccountItem>();
        using (SqlManager sql = new SqlManager(SqlManager.GetSqlDbiConnectionString()))
        {
            using (SqlDataReader reader = sql.ExecuteReader("SELECT A.Account_Id, A.Customer_Id, C.Last_Name + ', ' + C.First_Name AS CustomerName, A.[Status], AT.Name AS AcctType, A.Employee_Id, A.Initial_Balance, A.Interest_Rate, '$'+CONVERT(varchar(50), A.Balance, 1) AS Balance FROM Account A JOIN Account_Type AT ON A.Account_Type_Id=AT.Account_Type_Id JOIN Customer C ON A.Customer_Id=C.Customer_Id WHERE [Status]=1"))
            {
                while (reader.Read())
                {
                    AccountItem item = new AccountItem();
                    item.AccountId = (int)reader["Account_Id"];
                    item.CustomerId = (int)reader["Customer_Id"];
                    item.CustomerName = (string)reader["CustomerName"];
                    item.AccountStatus = (bool)reader["Status"];
                    item.AccountType = (string)reader["AcctType"];
                    item.InitialBalance = (decimal)reader["Initial_Balance"];
                    item.InterestRate = (decimal)reader["Interest_Rate"];
                    item.Balance = (string)reader["Balance"];

                    items.Add(item);
                }
                reader.Close();
            }
        }
        HttpContext.Current.Cache.Add(AccountItemsCacheKey, items.ToArray(), null, DateTime.Now.AddMinutes(CacheDuration), Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
        return items.ToArray();
    }
    else
    {
        return AccountItems;
    }
}

And here's one that never returns data:

[WebMethod]
public TransactionItem[] GetAllTransactions()
{
    TransactionItem[] tranItems = HttpContext.Current.Cache[TransactionItemsCacheKey] as TransactionItem[];

    if (tranItems == null)
    {
        List<TransactionItem> items = new List<TransactionItem>();
        using (SqlManager sql = new SqlManager(SqlManager.GetSqlDbiConnectionString()))
        {
            using (SqlDataReader reader = sql.ExecuteReader("SELECT [Transaction_Id],[Account_Id],[Amount],[DateTime],[Comment],TT.[Name] AS [TransType],[Flagged],[Employee_Id],[Status] FROM [Transaction] T JOIN [Trans_Type] TT ON T.Trans_Type_Id=TT.Trans_Type_Id"))
            {
                while (reader.Read())
                {
                    TransactionItem item = new TransactionItem();
                    item.TransactionId = (int)reader["Transaction_Id"];
                    item.AccountId = (int)reader["Account_Id"];
                    item.Amount = (decimal)reader["Amount"];
                    item.Timestamp = (DateTime)reader["DateTime"];
                    item.Comment = (string)reader["Comment"];
                    item.TransType = (string)reader["TransType"];
                    item.Flagged = (bool)reader["Flagged"];
                    item.EmployeeId = (int)reader["Employee_Id"];
                    item.Status = (bool)reader["Status"];

                    items.Add(item);
                }
                reader.Close();
            }
        }
        HttpContext.Current.Cache.Add(TransactionItemsCacheKey, items.ToArray(), null, DateTime.Now.AddMinutes(CacheDuration), Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
        return items.ToArray();
    }
    else
    {
        return tranItems;
    }
}

As you can see, they're almost identical. The SQL queries for both return a ton of records, but only the GetAllAccounts() WebMethod actually returns that data back.

This is how I'm displaying the data passed back from GetAllAccounts(), which works fine:

@{
    Layout = "~/Shared/_Layout.cshtml";
    Page.Title = "Accounts";
    Page.Header = "BankSite Mobile - Accounts";
    var svc = IntranetService.GetAllAccounts();
}
 <div data-role="content">
        <ul data-role="listview" data-inset="true" data-theme="c">
            @foreach(var item in svc){
                <li>
                    <h3><a href="Product.cshtml?acctid=@item.AccountId">Account #@item.AccountId.ToString() (@item.AccountType)</a></h3>
                    <p>Customer: @item.CustomerName</p>
                    <p>Account Balance: @item.Balance</p>
                </li>
            }
       </ul>
  </div>

Yet, this doesn't work fine, though it's the almost the exact same code:

@{
    Layout = "~/Shared/_Layout.cshtml";
    Page.Title = "Customers";
    Page.Header = "BankSite Mobile - Customers";
    var svc = IntranetService.GetAllCustomers();
}
 <div data-role="content">
        <ul data-role="listview" data-inset="true" data-theme="c">
            @foreach(var item in svc){
                <li>
                    <h3><a href="Product.cshtml?acctid=@item.CustomerId">Account #@item.CustomerId.ToString() (@item.CustomerId)</a></h3>
                    <p>Customer: @item.CustomerId</p>
                    <p>Account Balance: @item.CustomerId</p>
                </li>
            }
       </ul>
  </div>

...So basically I'm baffled. I don't understand why the data isn't being returned as expected from the non-working WebMethod (GetAllCustomers()). What am I missing?

Answer 1

I found the issue to be that some fields retrieved by the reader were null, and you can't create a null string. The solution was essentially to use something like this for every item property:

item.Amount = (reader["Amount"] != DBNull.value) ? (decimal)reader["Amount"] : 0;

Answer 2

Try to isolate the problem to the web service by accessing the web service directly in a web browser. Also, if possible, use SQL Server Profiler to make sure the web method is querying the database.

If it is not querying the database, then I would guess that it has already cached an empty array.

Therefore, the inital "if (tranItems == null)" check returns false, but it then returns an empty array as the results.

Answer 3

If you disable loading stuff from the cache, would both methods always succeed to return expected result set? I would try that first, my gut feeling is that something funky with the cache (i.e expires before your method returns). Then go from there.