better segregation of concern and interfaces.

MongoDbGenericRepository/DataAccess/Read/MongoDbReader.Main.cs

@@ -10,7 +10,7 @@ using System.Threading.Tasks;
 
 namespace MongoDbGenericRepository.DataAccess.Read
 {
-    public class MongoDbReader : DataAccessBase
+    public partial class MongoDbReader : DataAccessBase
     {
         public MongoDbReader(IMongoDbContext mongoDbContext) : base(mongoDbContext)
         {
@@ -390,4 +390,59 @@ namespace MongoDbGenericRepository.DataAccess.Read
 
         #endregion Sum TKey
     }
+
+    public partial class MongoDbReader
+    {
+        /// <summary>
+        /// Groups a collection of documents given a grouping criteria, 
+        /// and returns a dictionary of listed document groups with keys having the different values of the grouping criteria.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TGroupKey">The type of the grouping criteria.</typeparam>
+        /// <typeparam name="TProjection">The type of the projected group.</typeparam>
+        /// <param name="groupingCriteria">The grouping criteria.</param>
+        /// <param name="groupProjection">The projected group result.</param>
+        /// <param name="partitionKey">The partition key of your document, if any.</param>
+        public virtual List<TProjection> GroupBy<TDocument, TGroupKey, TProjection, TKey>(
+            Expression<Func<TDocument, TGroupKey>> groupingCriteria,
+            Expression<Func<IGrouping<TGroupKey, TDocument>, TProjection>> groupProjection,
+            string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+            where TProjection : class, new()
+        {
+            return HandlePartitioned<TDocument, TKey>(partitionKey)
+                             .Aggregate()
+                             .Group(groupingCriteria, groupProjection)
+                             .ToList();
+
+        }
+
+        /// <summary>
+        /// Groups filtered a collection of documents given a grouping criteria, 
+        /// and returns a dictionary of listed document groups with keys having the different values of the grouping criteria.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TGroupKey">The type of the grouping criteria.</typeparam>
+        /// <typeparam name="TProjection">The type of the projected group.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="selector">The grouping criteria.</param>
+        /// <param name="projection">The projected group result.</param>
+        /// <param name="partitionKey">The partition key of your document, if any.</param>
+        public virtual List<TProjection> GroupBy<TDocument, TGroupKey, TProjection, TKey>(
+            Expression<Func<TDocument, bool>> filter,
+            Expression<Func<TDocument, TGroupKey>> selector,
+            Expression<Func<IGrouping<TGroupKey, TDocument>, TProjection>> projection,
+            string partitionKey = null)
+                where TDocument : IDocument<TKey>
+                where TKey : IEquatable<TKey>
+                where TProjection : class, new()
+        {
+            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
+            return collection.Aggregate()
+                             .Match(Builders<TDocument>.Filter.Where(filter))
+                             .Group(selector, projection)
+                             .ToList();
+        }
+    }
 }

MongoDbGenericRepository/DataAccess/Read/MongoDbReader.Project.cs

@@ -0,0 +1,90 @@
+using MongoDB.Driver;
+using MongoDB.Driver.Linq;
+using MongoDbGenericRepository.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Threading.Tasks;
+
+namespace MongoDbGenericRepository.DataAccess.Read
+{
+    public partial class MongoDbReader
+    {
+        /// <summary>
+        /// Asynchronously returns a projected document matching the filter condition.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
+        /// <typeparam name="TProjection">The type representing the model you want to project to.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="projection">The projection expression.</param>
+        /// <param name="partitionKey">An optional partition key.</param>
+        public virtual async Task<TProjection> ProjectOneAsync<TDocument, TProjection, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TProjection>> projection, string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+            where TProjection : class
+        {
+            return await HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter)
+                                                                         .Project(projection)
+                                                                         .FirstOrDefaultAsync();
+        }
+
+        /// <summary>
+        /// Returns a projected document matching the filter condition.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
+        /// <typeparam name="TProjection">The type representing the model you want to project to.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="projection">The projection expression.</param>
+        /// <param name="partitionKey">An optional partition key.</param>
+        public virtual TProjection ProjectOne<TDocument, TProjection, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TProjection>> projection, string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+            where TProjection : class
+        {
+            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter)
+                                                                   .Project(projection)
+                                                                   .FirstOrDefault();
+        }
+
+        /// <summary>
+        /// Asynchronously returns a list of projected documents matching the filter condition.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
+        /// <typeparam name="TProjection">The type representing the model you want to project to.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="projection">The projection expression.</param>
+        /// <param name="partitionKey">An optional partition key.</param>
+        public virtual async Task<List<TProjection>> ProjectManyAsync<TDocument, TProjection, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TProjection>> projection, string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+            where TProjection : class
+        {
+            return await HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter)
+                                                                   .Project(projection)
+                                                                   .ToListAsync();
+        }
+
+        /// <summary>
+        /// Asynchronously returns a list of projected documents matching the filter condition.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
+        /// <typeparam name="TProjection">The type representing the model you want to project to.</typeparam>
+        /// <param name="filter">The document filter.</param>
+        /// <param name="projection">The projection expression.</param>
+        /// <param name="partitionKey">An optional partition key.</param>
+        public virtual List<TProjection> ProjectMany<TDocument, TProjection, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TProjection>> projection, string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+            where TProjection : class
+        {
+            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter)
+                                                                   .Project(projection)
+                                                                   .ToList();
+        }
+    }
+}