p450

I have tried the example, and it doesn't seem to work (tried the C# one, but the VB one appears to be identical)

As printed:

public void CBMethod(SQLAsynchResult ar)
{
SqlDataReader OrdersReader;
OrdersReader = ar.EndExecuteReader(ar);
gvOrders.DataSource = OrdersReader;
gvOrders.DataBind();
}

1 - VS2005 doesn't know "SQLAsynchResult"; is this "IAsyncResult"?
2 - With Option Strict in place, I can't run "OrdersReader = ar.EndExecuteReader(ar);" - it claims that I can't do this implicit conversion...I've tried to sort this out but haven't succeeded.

Anyone know what to do here?

Thanks

Griff



I can't find "SQLAsynchResult"; should it be "IAsyncResult"?

Okay - kinda answered this on my own, so thought I'd share it for comments (I might not have got this right of course !)

When I call the BeginExecuteReader, I have to use one of the overloaded methods, passing it a command object. I happen to be using a call back method that handles two different asynchronous DB calls, so also have to pass it the GridView name that I need populating. So, the following bit of code starts this process off:

        switch (CallBackMethodName)
        {
            case "CBAccounts":
                ASynchResult = Command.BeginExecuteReader(new AsyncCallback(CBHandler), new object[] { Command, gvAccounts }, CommandBehavior.CloseConnection);
                break;
            case "CBUsers":
                ASynchResult = Command.BeginExecuteReader(new AsyncCallback(CBHandler), new object[] { Command, gvUsers }, CommandBehavior.CloseConnection);
                break;
        }


Next, I have my method that handles the call back result:

    protected void CBHandler(IAsyncResult ar)
    {
        object[] args = (object[])ar.AsyncState;

        SqlCommand command = (SqlCommand)args[0];
        SqlDataReader AccountsReader = command.EndExecuteReader(ar);

        ((GridView)args[1]).DataSource = AccountsReader;
        ((GridView)args[1]).DataBind();
    }


One caveat - this example on p450 (well, my version of it) works when in debug mode, but when compiled it falls over.

The reason is that if the asynchronous data fetch hasn't completed by the time the page is ready to be sent to the browser then horrible things happen. I can get partially populated data-views or I can get a page error if the data simply hasn't returned in time.