Missed some files.

NTwain/IMemoryManager.cs

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+using System;
+namespace NTwain
+{
+    /// <summary>
+    /// Interface that provides the correct methods for managing memory on data exchanged with TWAIN sources.
+    /// </summary>
+    public interface IMemoryManager
+    {
+        /// <summary>
+        /// Function to allocate memory. Calls to this must be coupled with <see cref="MemFree"/> later.
+        /// </summary>
+        /// <param name="size">The size in bytes.</param>
+        /// <returns>Handle to the allocated memory.</returns>
+        IntPtr MemAllocate(uint size);
+
+        /// <summary>
+        /// Function to free memory. 
+        /// </summary>
+        /// <param name="handle">The handle from <see cref="MemAllocate"/>.</param>
+        void MemFree(IntPtr handle);
+
+        /// <summary>
+        /// Function to lock some memory. Calls to this must be coupled with <see cref="MemUnlock"/> later.
+        /// </summary>
+        /// <param name="handle">The handle to allocated memory.</param>
+        /// <returns>Handle to the lock.</returns>
+        IntPtr MemLock(IntPtr handle);
+
+        /// <summary>
+        /// Function to unlock a previously locked memory region.
+        /// </summary>
+        /// <param name="handle">The handle from <see cref="MemLock"/>.</param>
+        void MemUnlock(IntPtr handle);
+    }
+}