CSHARP-1191: Added DropAsync method to GridFSBucket.

Author: rstam

src/MongoDB.Driver.GridFS/GridFSBucket.cs

@@ -155,6 +155,23 @@ public ImmutableGridFSBucketOptions Options
             }
         }
 
+        /// <inheritdoc />
+        public async Task DropAsync(CancellationToken cancellationToken = default(CancellationToken))
+        {
+            var filesCollectionNamespace = GetFilesCollectionNamespace();
+            var chunksCollectionNamespace = GetChunksCollectionNamespace();
+            var messageEncoderSettings = GetMessageEncoderSettings();
+
+            using (var binding = await GetSingleServerReadWriteBindingAsync(cancellationToken).ConfigureAwait(false))
+            {
+                var filesCollectionDropOperation = new DropCollectionOperation(filesCollectionNamespace, messageEncoderSettings);
+                await filesCollectionDropOperation.ExecuteAsync(binding, cancellationToken).ConfigureAwait(false);
+
+                var chunksCollectionDropOperation = new DropCollectionOperation(chunksCollectionNamespace, messageEncoderSettings);
+                await chunksCollectionDropOperation.ExecuteAsync(binding, cancellationToken).ConfigureAwait(false);
+            }
+        }
+
         /// <inheritdoc />
         public async Task<IAsyncCursor<GridFSFileInfo>> FindAsync(FilterDefinition<GridFSFileInfo> filter, GridFSFindOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
         {

src/MongoDB.Driver.GridFS/IGridFSBucket.cs

@@ -90,6 +90,13 @@ public interface IGridFSBucket
         /// <returns>A Task.</returns>
         Task DownloadToStreamByNameAsync(string filename, Stream destination, GridFSDownloadByNameOptions options = null, CancellationToken cancellationToken = default(CancellationToken));
 
+        /// <summary>
+        /// Drops the files and chunks collections associated with this GridFS bucket.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>A Task.</returns>
+        Task DropAsync(CancellationToken cancellationToken = default(CancellationToken));
+
         /// <summary>
         /// Finds matching entries from the files collection.
         /// </summary>