add new method to support pagination

Microsoft.Azure.CosmosRepository.Samples/ServiceTier/Program.cs

@@ -7,6 +7,7 @@
 using System.Threading.Tasks;
 using Microsoft.Azure.Cosmos;
 using Microsoft.Azure.CosmosRepository;
+using Microsoft.Azure.CosmosRepository.Pagination;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -93,6 +94,15 @@ static async Task RawRepositoryExampleAsync(IRepository<Person> repository)
                 Console.WriteLine($"[Person] Updated: {person}");
             }
 
+            // Pagination read / verify pagination read
+            PagedResultRequest pagedResultRequest = new PagedResultRequest { SkipCount = 0, MaxResultCount = 2 };
+            PagedResult<Person> peopleWithPagedResult = await repository.GetListAsync(p => p.BirthDate > new DateTime(1970, 7, 21), pagedResultRequest);
+            Console.WriteLine($"[Person] Total Count: {peopleWithPagedResult.TotalCount}");
+            foreach (Person person in peopleWithPagedResult.Items)
+            {
+                Console.WriteLine($"[Person] Pagination Read: {person}");
+            }
+
             // Deleting...
             Console.WriteLine("[Person] Repository deleting...");
             await Task.WhenAll(new[]

Microsoft.Azure.CosmosRepository/src/DefaultRepository.cs

@@ -9,6 +9,7 @@
 using System.Threading.Tasks;
 using Microsoft.Azure.Cosmos;
 using Microsoft.Azure.Cosmos.Linq;
+using Microsoft.Azure.CosmosRepository.Pagination;
 using Microsoft.Azure.CosmosRepository.Extensions;
 using Microsoft.Azure.CosmosRepository.Options;
 using Microsoft.Azure.CosmosRepository.Providers;
@@ -98,6 +99,65 @@ public async ValueTask<IEnumerable<TItem>> GetAsync(
             return results;
         }
 
+        /// <inheritdoc/>
+        public async Task<PagedResult<TItem>> GetListAsync<TPagedRequest>(
+            Expression<Func<TItem, bool>> predicate,
+            TPagedRequest pagedResultRequest,
+            CancellationToken cancellationToken = default)
+        {
+            Container container =
+                await _containerProvider.GetContainerAsync().ConfigureAwait(false);
+
+            IQueryable<TItem> query =
+                container.GetItemLinqQueryable<TItem>()
+                    .Where(predicate.Compose(
+                        item => !item.Type.IsDefined() || item.Type == typeof(TItem).Name, Expression.AndAlso));
+
+            Response<int> response = await query.CountAsync(cancellationToken);
+            int totalCount = response.Resource;
+
+            query = ApplyPaging(query, pagedResultRequest);
+
+            TryLogDebugDetails(_logger, () => $"Read: {query}");
+
+            using FeedIterator<TItem> iterator = query.ToFeedIterator();
+            List<TItem> results = new();
+            while (iterator.HasMoreResults)
+            {
+                foreach (TItem result in await iterator.ReadNextAsync(cancellationToken).ConfigureAwait(false))
+                {
+                    results.Add(result);
+                }
+            }
+            return new PagedResult<TItem>(totalCount, results);
+        }
+
+        protected virtual IQueryable<TItem> ApplyPaging<TPagedRequest>(
+            IQueryable<TItem> query,
+            TPagedRequest pagedResultRequest)
+        {
+            //Try to use paging if available
+            if (pagedResultRequest is IPagedResultRequest pagedInput)
+            {
+                return query.Skip(pagedInput.SkipCount).Take(pagedInput.MaxResultCount);
+            }
+
+            //Try to limit query result if available
+            if (pagedResultRequest is ILimitedResultRequest limitedInput)
+            {
+                return query.Take(limitedInput.MaxResultCount);
+            }
+
+            //Try to skip if available
+            if (pagedResultRequest is ISkippedResultRequest skippedInput)
+            {
+                return query.Skip(skippedInput.SkipCount);
+            }
+
+            //No paging
+            return query;
+        }
+
         /// <inheritdoc/>
         public async ValueTask<IEnumerable<TItem>> GetByQueryAsync(
             string query,
@@ -232,4 +292,4 @@ static void TryLogDebugDetails(ILogger logger, Func<string> getMessage)
             }
         }
     }
-}
+}

Microsoft.Azure.CosmosRepository/src/IRepository.cs

@@ -7,6 +7,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Azure.Cosmos;
+using Microsoft.Azure.CosmosRepository.Pagination;
+
 
 namespace Microsoft.Azure.CosmosRepository
 {
@@ -61,6 +63,18 @@ ValueTask<TItem> GetAsync(
             PartitionKey partitionKey,
             CancellationToken cancellationToken = default);
 
+        /// <summary>
+        /// Gets an <see cref="PagedResult{TItem}"/> of <see cref="IItem"/>
+        /// </summary>
+        /// <param name="predicate">The expression used for evaluating a matching item.</param>
+        /// <param name="pagedResultRequest">The paging object.</param>
+        /// <param name="cancellationToken">The cancellation token to use when making asynchronous operations.</param>
+        /// <returns>A paged result of item instances who meet the <paramref name="predicate"/> and <paramref name="pagedResultRequest"/> condition.</returns>
+        Task<PagedResult<TItem>> GetListAsync<TPagedRequest>(
+            Expression<Func<TItem, bool>> predicate,
+            TPagedRequest pagedResultRequest,
+            CancellationToken cancellationToken = default);
+
         /// <summary>
         /// Gets an <see cref="IEnumerable{TItem}"/> collection of <see cref="IItem"/>
         /// implementation classes that match the given <paramref name="predicate"/>.
@@ -161,4 +175,4 @@ ValueTask DeleteAsync(
             PartitionKey partitionKey,
             CancellationToken cancellationToken = default);
     }
-}
+}

Microsoft.Azure.CosmosRepository/src/Pagination/ILimitedResultRequest.cs

@@ -0,0 +1,17 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <summary>
+    /// This interface is defined to standardize to request a limited result.
+    /// </summary>
+    public interface ILimitedResultRequest
+    {
+        /// <summary>
+        /// Maximum result count should be returned.
+        /// This is generally used to limit result count on paging.
+        /// </summary>
+        int MaxResultCount { get; set; }
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/IPagedResultRequest.cs

@@ -0,0 +1,12 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <summary>
+    /// This interface is defined to standardize to request a paged result.
+    /// </summary>
+    public interface IPagedResultRequest : ISkippedResultRequest, ILimitedResultRequest
+    {
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/ISkippedResultRequest.cs

@@ -0,0 +1,14 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <summary>
+    /// This interface is defined to standardize to request a skipped result.
+    /// </summary>
+    public interface ISkippedResultRequest
+    {
+        /// <inheritdoc />
+        int SkipCount { get; set; }
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/LimitedResultRequest.cs

@@ -0,0 +1,17 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <inheritdoc />
+    public class LimitedResultRequest : ILimitedResultRequest
+    {
+        /// <summary>
+        /// Default value: 10.
+        /// </summary>
+        public static int DefaultMaxResultCount { get; set; } = 10;
+
+        /// <inheritdoc />
+        public int MaxResultCount { get; set; } = DefaultMaxResultCount;
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/ListResult.cs

@@ -0,0 +1,27 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <summary>
+    /// List of items
+    /// </summary>
+    public class ListResult<T>
+    {
+        /// <summary>
+        /// Creates a new <see cref="ListResult{T}"/> object.
+        /// </summary>
+        public ListResult() { }
+
+        /// <summary>
+        /// Creates a new <see cref="ListResult{T}"/> object.
+        /// </summary>
+        /// <param name="items">List of items</param>
+        public ListResult(IReadOnlyList<T> items) => Items = items;
+
+        /// <inheritdoc />
+        public IReadOnlyList<T> Items { get; internal set; } = new List<T>();
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/PagedResult.cs

@@ -0,0 +1,28 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <inheritdoc />
+    public class PagedResult<T> : ListResult<T>
+    {
+        /// <inheritdoc />
+        public long TotalCount { get; internal set; }
+
+        /// <summary>
+        /// Creates a new <see cref="PagedResult{T}"/> object.
+        /// </summary>
+        public PagedResult() { }
+
+        /// <summary>
+        /// Creates a new <see cref="PagedResult{T}"/> object.
+        /// </summary>
+        /// <param name="totalCount">Total count of Items</param>
+        /// <param name="items">List of items in current page</param>
+        public PagedResult(long totalCount, IReadOnlyList<T> items)
+            : base(items) =>
+            TotalCount = totalCount;
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/PagedResultRequest.cs

@@ -0,0 +1,12 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <inheritdoc />
+    public class PagedResultRequest : LimitedResultRequest, IPagedResultRequest
+    {
+        /// <inheritdoc />
+        public int SkipCount { get; set; }
+    }
+}

Microsoft.Azure.CosmosRepository/src/Pagination/SkippedResultRequest.cs

@@ -0,0 +1,12 @@
+// Copyright (c) IEvangelist. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Azure.CosmosRepository.Pagination
+{
+    /// <inheritdoc />
+    public class SkippedResultRequest : ISkippedResultRequest
+    {
+        /// <inheritdoc />
+        public int SkipCount { get; set; }
+    }
+}