Question

我尝试使用NHibernate执行HQL查询。当我尝试执行查询时会引发异常，我无法理解问题所在。

HQL查询。

public class UsuarioDAO : ImplementacaoPersist<Usuario>{

        public IList<Usuario> findByText(string text) {
            ISession _session = BDConnect.openSession();
            IList<Usuario> list = (IList<Usuario>)_session.CreateQuery("from Usuario u WHERE u.nome LIKE :nome OR u.login LIKE :login")
                                                                        .SetParameter("nome", "%" + text + "%")
                                                                        .SetParameter("login", "%" + text + "%");
            return list;
        }
    }

例外

System.Transactions Critical: 0 : <TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Critical"><TraceIdentifier>http://msdn.microsoft.com/TraceCodes/System/ActivityTracing/2004/07/Reliability/Exception/Unhandled</TraceIdentifier><Description>Unhandled exception</Description><AppDomain>ControleUsuarios.vshost.exe</AppDomain><Exception><ExceptionType>System.InvalidCastException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType><Message>Unable to cast object of type 'NHibernate.Impl.QueryImpl' to type 'System.Collections.Generic.IList`1[ControleUsuarios.Domain.Usuario]'.</Message><StackTrace>   at ControleUsuarios.Implementacao.UsuarioDAO.findByText(String text) in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Implementacao\UsuarioDAO.cs:line 18
   at ControleUsuarios.Form1.txtSearch_KeyUp(Object sender, KeyEventArgs e) in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Form1.cs:line 80
   at System.Windows.Forms.Control.OnKeyUp(KeyEventArgs e)
   at System.Windows.Forms.Control.ProcessKeyEventArgs(Message&amp;amp; m)
   at System.Windows.Forms.Control.ProcessKeyMessage(Message&amp;amp; m)
   at System.Windows.Forms.Control.WmKeyChar(Message&amp;amp; m)
   at System.Windows.Forms.Control.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.TextBoxBase.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.TextBox.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp;amp; m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&amp;amp; msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr 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 ControleUsuarios.Program.Main() in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Program.cs:line 16
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly 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.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()</StackTrace><ExceptionString>System.InvalidCastException: Unable to cast object of type 'NHibernate.Impl.QueryImpl' to type 'System.Collections.Generic.IList`1[ControleUsuarios.Domain.Usuario]'.
   at ControleUsuarios.Implementacao.UsuarioDAO.findByText(String text) in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Implementacao\UsuarioDAO.cs:line 18
   at ControleUsuarios.Form1.txtSearch_KeyUp(Object sender, KeyEventArgs e) in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Form1.cs:line 80
   at System.Windows.Forms.Control.OnKeyUp(KeyEventArgs e)
   at System.Windows.Forms.Control.ProcessKeyEventArgs(Message&amp;amp; m)
   at System.Windows.Forms.Control.ProcessKeyMessage(Message&amp;amp; m)
   at System.Windows.Forms.Control.WmKeyChar(Message&amp;amp; m)
   at System.Windows.Forms.Control.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.TextBoxBase.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.TextBox.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp;amp; m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp;amp; m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&amp;amp; msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr 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 ControleUsuarios.Program.Main() in c:\Users\fernando\Documents\Visual Studio 2012\Projects\ControleUsuarios\ControleUsuarios\Program.cs:line 16
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly 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.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()</ExceptionString></Exception></TraceRecord>
The program '[2584] ControleUsuarios.vshost.exe: Program Trace' has exited with code 0 (0x0).
The program '[2584] ControleUsuarios.vshost.exe: Managed (v4.0.30319)' has exited with code -1 (0xffffffff).

Answer 1

您正在将查询对象强制转换为List。这不是您应该如何执行查询。

从您的日志开始：System.InvalidCastException然后Unable to cast object of type 'NHibernate.Impl.QueryImpl' to type 'System.Collections.Generic.IList。

请参阅doc。你的代码应该是：

var list = _session
    .CreateQuery("from Usuario u WHERE u.nome LIKE :nome OR u.login LIKE :login")
    .SetParameter("nome", "%" + text + "%")
    .SetParameter("login", "%" + text + "%")
    .List<Usuario>();

旁注：我猜您的示例代码不仅仅是一个示例，但为了以防万一，请确保您的实际代码不会忘记关闭/处理会话。

您也可以考虑使用除HQL之外的其他查询API。就个人而言，我倾向于只在named queries使用HQL。在代码中，我主要使用linq-to-nhibernate。

using NHibernate.Linq;
...

var list = _session
    .Query<Usuario>()
    .Where(u => u.nome.Contains(text) || u.login.Contains(text))
    .ToList();

但您也可以使用Criteria或QueryOver。

如何使用IList与HQL查询和NHibernate？

1 个答案: