CacheBase changes

- regrouped members
- virtual members that had NotSupportedException as default implementation replaced with abstract
- correct copyright

Author: alex-kulakov

Orm/Xtensive.Orm/Caching/CacheBase.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2007-2021 Xtensive LLC.
+// Copyright (C) 2021 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 
@@ -16,25 +16,25 @@ public abstract class CacheBase<TKey, TItem> : ICache<TKey, TItem>
     public virtual Converter<TItem, TKey> KeyExtractor { [DebuggerStepThrough]get; protected set; }
 
     /// <inheritdoc/>
-    public virtual TItem this[TKey key, bool markAsHit] => TryGetItem(key, markAsHit, out var item) ? item : default;
+    public abstract int Count { get; }
 
     /// <inheritdoc/>
-    public abstract int Count { get; }
+    public virtual TItem this[TKey key, bool markAsHit] => TryGetItem(key, markAsHit, out var item) ? item : default;
 
     /// <inheritdoc/>
-    public abstract TItem Add(TItem item, bool replaceIfExists);
+    public abstract bool TryGetItem(TKey key, bool markAsHit, out TItem item);
 
     /// <inheritdoc/>
-    public virtual void Add(TItem item) => Add(item, true);
+    public abstract bool ContainsKey(TKey key);
 
     /// <inheritdoc/>
-    public virtual void Clear() => throw new NotImplementedException();
+    public abstract TItem Add(TItem item, bool replaceIfExists);
 
     /// <inheritdoc/>
-    public virtual bool ContainsKey(TKey key) => throw new NotImplementedException();
+    public virtual void Add(TItem item) => Add(item, true);
 
     /// <inheritdoc/>
-    public virtual IEnumerator<TItem> GetEnumerator() => throw new NotImplementedException();
+    public abstract void Clear();
 
     /// <inheritdoc/>
     public virtual void Remove(TItem item)
@@ -50,7 +50,7 @@ public virtual void Remove(TItem item)
     public abstract void RemoveKey(TKey key, bool removeCompletely);
 
     /// <inheritdoc/>
-    public abstract bool TryGetItem(TKey key, bool markAsHit, out TItem item);
+    public abstract IEnumerator<TItem> GetEnumerator();
   }
 }