BitmapMetadataEnumerator.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media / Imaging / BitmapMetadataEnumerator.cs / 1305600 / BitmapMetadataEnumerator.cs
                        
                        
                            //------------------------------------------------------------------------------ 
//  Microsoft Windows Client Platform
//  Copyright (c) Microsoft Corporation, 2005
//
//  File:       BitmapMetadataEnumerator.cs 
//-----------------------------------------------------------------------------
 
// Allow suppression of certain presharp messages 
#pragma warning disable 1634, 1691
 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices; 
using System.Security;
using System.Security.Permissions; 
using System.Diagnostics; 
using MS.Internal;
using MS.Internal.PresentationCore;                        // SecurityHelper 
using MS.Win32.PresentationCore;

using SR=MS.Internal.PresentationCore.SR;
using SRID=MS.Internal.PresentationCore.SRID; 

namespace System.Windows.Media.Imaging 
{ 
    /// 
    /// An enumerator that iterates over the children of a timeline. 
    /// 
    internal struct BitmapMetadataEnumerator : IEnumerator, IEnumerator
    {
        #region External interface 

        #region IEnumerator interface 
 
        #region Properties
 
        /// 
        /// Gets the current element in the collection.
        /// 
        ///  
        /// The current element in the collection.
        ///  
        ///  
        /// Critical - Accesses unmanaged code
        /// TreatAsSafe - inputs are verified or safe 
        /// 
        object IEnumerator.Current
        {
            [SecurityCritical, SecurityTreatAsSafe] 
            get
            { 
                return Current; 
            }
        } 

        #endregion // Properties

        #region Methods 

        ///  
        /// Advances the enumerator to the next element of the collection. 
        /// 
        ///  
        /// True if the enumerator was successfully advanced to the next element;
        /// false if the enumerator has passed the end of the collection.
        /// 
        ///  
        /// Critical - Accesses unmanaged code
        /// TreatAsSafe - inputs are verified or safe 
        ///  
        [SecurityCritical, SecurityTreatAsSafe]
        public bool MoveNext() 
        {
            if (_fStarted && _current == null)
            {
                return false; 
            }
 
            _fStarted = true; 

            IntPtr ppStr = IntPtr.Zero; 
            Int32 celtFetched = 0;

            try
            { 
                int hr = UnsafeNativeMethods.EnumString.Next(
                    _enumeratorHandle, 
                    1, 
                    ref ppStr,
                    ref celtFetched); 

                if (HRESULT.IsWindowsCodecError(hr))
                {
                    _current = null; 
                    return false;
                } 
 
                HRESULT.Check(hr);
 
                if (celtFetched == 0)
                {
                    _current = null;
                    return false; 
                }
                else 
                { 
                    _current = Marshal.PtrToStringUni(ppStr);
                } 
            }
            finally
            {
                if (ppStr != IntPtr.Zero) 
                {
                    Marshal.FreeCoTaskMem(ppStr); 
                    ppStr = IntPtr.Zero; 
                }
            } 

            return true;
        }
 
        /// 
        /// Sets the enumerator to its initial position, which is before the first element 
        /// in the collection. 
        /// 
        ///  
        /// Critical - Accesses unmanaged code
        /// TreatAsSafe - inputs are verified or safe
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        public void Reset()
        { 
            HRESULT.Check(UnsafeNativeMethods.EnumString.Reset(_enumeratorHandle)); 

            _current = null; 
            _fStarted = false;
        }

        #endregion // Methods 

        #endregion // IEnumerator interface 
 
        #region Properties
 
        /// 
        /// The current timeline referenced by this enumerator.
        /// 
        public String Current 
        {
            get 
            { 
                if (_current == null)
                { 
                    if (!_fStarted)
                    {
#pragma warning suppress 56503 // Suppress presharp warning: Follows a pattern similar to Nullable.
                    throw new InvalidOperationException(SR.Get(SRID.Enumerator_NotStarted)); 
                    }
                    else 
                    { 
#pragma warning suppress 56503 // Suppress presharp warning: Follows a pattern similar to Nullable.
                    throw new InvalidOperationException(SR.Get(SRID.Enumerator_ReachedEnd)); 
                    }
                }

                return _current; 
            }
        } 
 
        /// 
        /// 
        /// 
        void IDisposable.Dispose()
        {
            // Do nothing - Required by the IEnumerable contract. 
        }
 
        #endregion // Properties 

        #endregion // External interface 

        #region Internal implementation

        #region Construction 

        ///  
        /// Creates an enumerator iterates over the children of the specified container. 
        /// 
        ///  
        /// Handle to a metadata query reader/writer
        /// 
        /// 
        /// Critical - Accesses unmanaged code 
        /// TreatAsSafe - inputs are verified or safe
        ///  
        [SecurityCritical, SecurityTreatAsSafe] 
        internal BitmapMetadataEnumerator(SafeMILHandle metadataHandle)
        { 
            Debug.Assert(metadataHandle != null && !metadataHandle.IsInvalid);

            HRESULT.Check(UnsafeNativeMethods.WICMetadataQueryReader.GetEnumerator(
                metadataHandle, 
                out _enumeratorHandle));
 
            _current = null; 
            _fStarted = false;
        } 

        #endregion // Construction

        #region Methods 

        #endregion // Methods 
 
        #region Data
 
        /// 
        /// Critical - pointer to an unmanaged object that methods are called on.
        /// 
        [SecurityCritical] 
        private SafeMILHandle _enumeratorHandle;
 
        private String _current; 
        private bool _fStarted;
 
        #endregion // Data

        #endregion // Internal implementation
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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