Closes #33 - The in-memory file based system needs to reload only when the file changes

Author: johelvisguzman

src/DotNetToolkit.Repository.InMemory/InMemoryFileBasedRepositoryBase.cs

@@ -92,21 +92,34 @@ private void OnInitialize(string filePath)
             // Otherwise, try to get the data from the file
             else
             {
-                // Adds the data from the file into memory
-                using (var stream = new FileStream(DatabaseName, FileMode.Open, FileAccess.Read))
-                using (var reader = new StreamReader(stream))
+                // Checks to see when was the last time that the file was updated. If the TimeStamp and the lastWriteTime
+                // are the same, then it means that the file has only been updated by this repository; otherwise,
+                // something else updated it (maybe a manual edit). In which case, we need to re-upload the entities into memory
+                var lastWriteTime = File.GetLastWriteTime(DatabaseName);
+                var timetamp = GetTimeStamp();
+                if (!lastWriteTime.Equals(timetamp))
                 {
-                    var entities = OnLoaded(reader);
+                    LoadChanges();
+                }
+            }
+        }
 
-                    EnsureDeleted();
+        private void LoadChanges()
+        {
+            // Adds the data from the file into memory
+            using (var stream = new FileStream(DatabaseName, FileMode.Open, FileAccess.Read))
+            using (var reader = new StreamReader(stream))
+            {
+                var entities = OnLoaded(reader);
 
-                    foreach (var entity in entities)
-                    {
-                        AddItem(entity);
-                    }
+                EnsureDeleted();
 
-                    base.SaveChanges();
+                foreach (var entity in entities)
+                {
+                    AddItem(entity);
                 }
+
+                base.SaveChanges();
             }
         }
 
@@ -131,6 +144,8 @@ protected override void SaveChanges()
 
                     OnSaved(writer, entities);
                 }
+
+                SetTimeStamp(File.GetLastWriteTime(DatabaseName));
             }
         }
 

src/DotNetToolkit.Repository.InMemory/InMemoryRepositoryBase.cs

@@ -79,6 +79,24 @@ internal void EnsureDeleted()
             InMemoryCache<TEntity, TKey>.Instance.GetContext(DatabaseName).Clear();
         }
 
+        /// <summary>
+        /// Sets the time stamp.
+        /// </summary>
+        /// <param name="time">The time.</param>
+        internal void SetTimeStamp(DateTime time)
+        {
+            InMemoryCache<TEntity, TKey>.Instance.SetTimeStamp(DatabaseName, time);
+        }
+
+        /// <summary>
+        /// Gets the time stamp.
+        /// </summary>
+        /// <returns>The time stamp.</returns>
+        internal DateTime GetTimeStamp()
+        {
+            return InMemoryCache<TEntity, TKey>.Instance.GetTimeStamp(DatabaseName);
+        }
+
         #endregion
 
         #region	Private Methods
@@ -230,6 +248,8 @@ protected override void SaveChanges()
                     }
                 }
 
+                SetTimeStamp(DateTime.Now);
+
                 _context.Clear();
             }
         }
@@ -333,6 +353,7 @@ private class InMemoryCache<TEntity, TKey> where TEntity : class
             private static volatile InMemoryCache<TEntity, TKey> _instance;
             private static readonly object _syncRoot = new object();
             private readonly ConcurrentDictionary<string, SortedDictionary<TKey, TEntity>> _storage;
+            private readonly ConcurrentDictionary<string, DateTime> _timestamp;
 
             #endregion
 
@@ -344,6 +365,7 @@ private class InMemoryCache<TEntity, TKey> where TEntity : class
             private InMemoryCache()
             {
                 _storage = new ConcurrentDictionary<string, SortedDictionary<TKey, TEntity>>();
+                _timestamp = new ConcurrentDictionary<string, DateTime>();
             }
 
             #endregion
@@ -389,6 +411,28 @@ public SortedDictionary<TKey, TEntity> GetContext(string name)
                 return _storage[name];
             }
 
+            /// <summary>
+            /// Sets the time stamp.
+            /// </summary>
+            /// <param name="name">The database name.</param>
+            /// <param name="time">The time.</param>
+            public void SetTimeStamp(string name, DateTime time)
+            {
+                _timestamp[name] = time;
+            }
+
+            /// <summary>
+            /// Gets the time stamp.
+            /// </summary>
+            /// <param name="name">The database name.</param>
+            /// <returns>The time stamp.</returns>
+            public DateTime GetTimeStamp(string name)
+            {
+                _timestamp.TryGetValue(name, out DateTime time);
+
+                return time;
+            }
+
             #endregion
         }
 

version.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>2.1.0</VersionPrefix>
+    <VersionPrefix>2.1.1</VersionPrefix>
     <VersionSuffix></VersionSuffix>
   </PropertyGroup>
 </Project>