Unable to Retrieve Objects

Gortok · **Joined:** Sun Jan 21, 2007 4:33 pm **Posts:** 65

Greetings:

I'm trying to retrieve the Client object from the database based on the "ClientSSN" field. The customer wants to search by Social, which as a matter of design is not the PK for the Database.

Here's the query I'm using:

Code:

            ICriteria criteria = session.CreateCriteria(typeof(Client));
            criteria.Add(NHibernate.Expression.Expression.Eq("ClientSSN", txtClientSSN.Text));
            IList client = criteria.List();

I get the following Error from the compiler (that admittedly, I don't understand and Google isn't providing much help:

Code:

Error   1   Using the generic type 'System.Collections.Generic.IList<T>' requires '1' type arguments

Finally, if there's a better way to retrieve an object from the DB where you know you will only retrieve one set of records, please let me know. In my searches, I'm not interested in retrieving more than one client at a time, I just want to load the client into the app by inputting their SSN.

Thanks in advance.

mnichols · **Joined:** Mon Aug 21, 2006 9:18 am **Posts:** 179

Use session.UniqueResult<T> for retrieving a single result. It'll throw if it finds more than one match.
The compiler is complaining because you are retrieving an ArrayList from NHibernate using criteria.List() when what you coded is an generic IList<T>. Use criteria.List<T>() instead.

Gortok · **Joined:** Sun Jan 21, 2007 4:33 pm **Posts:** 65

Code:

Client client = (Client)session.CreateQuery(
      "select client from Client as client where client.ClientSSN = ?")
      .SetEntity("ClientSSN", txtClientSSN.Text)
      .UniqueResult();

That above is the query. Essentially, I'm trying to grab the object client from the DB (because I'll want to load all properties of that client into textfields and the like), well, it's giving me this exception when I use it at runtime:

Code:

"Not all named parameters have been set: [] [select client from Client as client where client.ClientSSN = ?]"

I'm missing something, aren't I. Errgh. I'm probably just tired, I've been fooling with this most of the night.

mnichols · **Joined:** Mon Aug 21, 2006 9:18 am **Posts:** 179

try this in HQL

Code:

Client client = (Client)session.CreateQuery("from Client where ClientSSN = :ssn").SetParameter("ssn",txtClientSSN.Text);

This is using named parameters to pass into the query.
You could use the ICriteria route too:

Code:

ICriteria crit = session.CreateCriteria(typeof(Client)).Add(Expression.Eq("ClientSSN",txtClientSSN.Text));

Hope this helps
MIKE

Gortok · **Joined:** Sun Jan 21, 2007 4:33 pm **Posts:** 65

Mike, thanks for your help thus far. I like your solution, I hit a snag with it:

Code:

System.InvalidCastException was unhandled
  Message="Unable to cast object of type 'NHibernate.Impl.QueryImpl' to type 'SocksCDS.Client'."
  Source="Socks CDS"
  StackTrace:
       at SocksCDS.Form2.btnRetrieveClient_Click(Object sender, EventArgs e) in C:\Code Projects\New Socks CDS\Socks CDS\Form2.cs:line 276
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at SocksCDS.Program.Main() in C:\Code Projects\New Socks CDS\Socks CDS\Program.cs:line 27
       at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()

Google isn't very helpful with this exception.

mnichols · **Joined:** Mon Aug 21, 2006 9:18 am **Posts:** 179

Can you post your code that is used ?
It looks like you used the HQL I wrote...try this

Code:

Client client = (Client)session.CreateQuery("from Client where ClientSSN = :ssn").SetParameter("ssn",txtClientSSN.Text).UniqueResult<Client>();

I forgot the UniqueResult<T> bit at the end.
MIKE

Gortok · **Joined:** Sun Jan 21, 2007 4:33 pm **Posts:** 65

Thanks M. You helped a bit. :-)