// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
/*============================================================
**
** Class: EventLogPropertySelector
**
** Purpose: 
** Public class that encapsulates the information for fast 
** access to Event Values of an EventLogRecord. Implements
** the EventPropertyContext abstract class.  An instance of this 
** class is constructed and then passed to 
** EventLogRecord.GetEventPropertyValues.
**
============================================================*/
using System;
using System.Collections.Generic;
using Microsoft.Win32;
 
namespace System.Diagnostics.Eventing.Reader {
 
    /// <summary>
    ///  Encapsulates the information for fast access to Event Values 
    ///  of an EventLogRecord.  An instance of this class is constructed
    ///  and then passed to EventLogRecord.GetEventPropertyValues.
    /// </summary>
    [System.Security.Permissions.HostProtection(MayLeakOnAbort = true)]
    public class EventLogPropertySelector : IDisposable {
 
        //
        // access to the data member reference is safe, while 
        // invoking methods on it is marked SecurityCritical as appropriate.
        //
        private EventLogHandle renderContextHandleValues;
 
        [System.Security.SecurityCritical]
        public EventLogPropertySelector(IEnumerable<string> propertyQueries) {
 
            EventLogPermissionHolder.GetEventLogPermission().Demand();
 
            if (propertyQueries == null)
                throw new ArgumentNullException("propertyQueries");
 
            string[] paths;
 
            ICollection<string> coll = propertyQueries as ICollection<string>;
            if (coll != null) {
                paths = new string[coll.Count];
                coll.CopyTo(paths, 0);
            }
            else {
                List<string> queries;
                queries = new List<string>(propertyQueries);
                paths = queries.ToArray();
            }
 
            renderContextHandleValues = NativeWrapper.EvtCreateRenderContext(paths.Length, paths, UnsafeNativeMethods.EvtRenderContextFlags.EvtRenderContextValues);
        }
 
        internal EventLogHandle Handle {
            // just returning reference to security critical type, the methods
            // of that type are protected by SecurityCritical as appropriate.
            get {
                return renderContextHandleValues;
            }
        }
 
        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
 
        [System.Security.SecuritySafeCritical]
        protected virtual void Dispose(bool disposing) {
            if (disposing) {
                EventLogPermissionHolder.GetEventLogPermission().Demand();
            }
            if (renderContextHandleValues != null && !renderContextHandleValues.IsInvalid)      
                renderContextHandleValues.Dispose();
        }
    }
}