docs: document pagination result APIs

Author: landeqiming666

QueryBuilder.Tests/PaginationResultTests.cs

@@ -0,0 +1,75 @@
+using System.Linq;
+using SqlKata.Execution;
+using Xunit;
+
+namespace SqlKata.Tests
+{
+    public class PaginationResultTests
+    {
+        [Fact]
+        public void ReportsPageStateFromCountAndPageSize()
+        {
+            var result = new PaginationResult<int>
+            {
+                Count = 25,
+                Page = 2,
+                PerPage = 10,
+            };
+
+            Assert.Equal(3, result.TotalPages);
+            Assert.False(result.IsFirst);
+            Assert.False(result.IsLast);
+            Assert.True(result.HasNext);
+            Assert.True(result.HasPrevious);
+        }
+
+        [Fact]
+        public void BuildsQueriesForAdjacentPages()
+        {
+            var nextResult = new PaginationResult<int>
+            {
+                Query = new Query("Posts"),
+                Page = 2,
+                PerPage = 10,
+            };
+
+            var nextQuery = nextResult.NextQuery();
+
+            Assert.Same(nextResult.Query, nextQuery);
+            Assert.Equal(20, nextQuery.GetOffset());
+            Assert.Equal(10, nextQuery.GetLimit());
+
+            var previousResult = new PaginationResult<int>
+            {
+                Query = new Query("Posts"),
+                Page = 2,
+                PerPage = 10,
+            };
+
+            var previousQuery = previousResult.PreviousQuery();
+
+            Assert.Same(previousResult.Query, previousQuery);
+            Assert.Equal(0, previousQuery.GetOffset());
+            Assert.Equal(10, previousQuery.GetLimit());
+        }
+
+        [Fact]
+        public void EachYieldsTheCurrentPageWhenThereIsNoNextPage()
+        {
+            var result = new PaginationResult<int>
+            {
+                Count = 2,
+                List = new[] { 1, 2 },
+                Page = 1,
+                PerPage = 10,
+            };
+
+            var iterator = result.Each;
+            var pages = iterator.ToList();
+
+            Assert.Single(pages);
+            Assert.Same(result, pages[0]);
+            Assert.Same(result, iterator.CurrentPage);
+        }
+    }
+}

SqlKata.Execution/PaginationIterator.cs

@@ -3,11 +3,27 @@
 
 namespace SqlKata.Execution
 {
+    /// <summary>
+    /// Enumerates paginated results, beginning with a supplied first page and
+    /// loading each subsequent page as enumeration advances.
+    /// </summary>
+    /// <typeparam name="T">The type of each item in the paginated results.</typeparam>
     public class PaginationIterator<T> : IEnumerable<PaginationResult<T>>
     {
+        /// <summary>
+        /// Gets or sets the page from which enumeration starts.
+        /// </summary>
         public PaginationResult<T> FirstPage { get; set; }
+
+        /// <summary>
+        /// Gets or sets the page most recently returned by the iterator.
+        /// </summary>
         public PaginationResult<T> CurrentPage { get; set; }
 
+        /// <summary>
+        /// Returns an enumerator that yields the first page and loads later pages on demand.
+        /// </summary>
+        /// <returns>An enumerator over the available pages.</returns>
         public IEnumerator<Execution.PaginationResult<T>> GetEnumerator()
         {
             CurrentPage = FirstPage;

SqlKata.Execution/PaginationResult.cs

@@ -6,13 +6,41 @@
 
 namespace SqlKata.Execution
 {
+    /// <summary>
+    /// Represents one page of query results together with pagination metadata
+    /// and helpers for loading adjacent pages.
+    /// </summary>
+    /// <typeparam name="T">The type of each item in the result set.</typeparam>
     public class PaginationResult<T>
     {
+        /// <summary>
+        /// Gets or sets the query used to produce the paginated results.
+        /// </summary>
         public Query Query { get; set; }
+
+        /// <summary>
+        /// Gets or sets the total number of matching records across all pages.
+        /// </summary>
         public long Count { get; set; }
+
+        /// <summary>
+        /// Gets or sets the records in the current page.
+        /// </summary>
         public IEnumerable<T> List { get; set; }
+
+        /// <summary>
+        /// Gets or sets the one-based current page number.
+        /// </summary>
         public int Page { get; set; }
+
+        /// <summary>
+        /// Gets or sets the maximum number of records per page.
+        /// </summary>
         public int PerPage { get; set; }
+
+        /// <summary>
+        /// Gets the total number of pages, rounded up from <see cref="Count"/>.
+        /// </summary>
         public int TotalPages
         {
             get
@@ -30,6 +58,9 @@ public int TotalPages
             }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether this is the first page.
+        /// </summary>
         public bool IsFirst
         {
             get
@@ -38,6 +69,9 @@ public bool IsFirst
             }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether this is the last page.
+        /// </summary>
         public bool IsLast
         {
             get
@@ -46,6 +80,9 @@ public bool IsLast
             }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether a page follows the current page.
+        /// </summary>
         public bool HasNext
         {
             get
@@ -54,6 +91,9 @@ public bool HasNext
             }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether a page precedes the current page.
+        /// </summary>
         public bool HasPrevious
         {
             get
@@ -62,36 +102,73 @@ public bool HasPrevious
             }
         }
 
+        /// <summary>
+        /// Applies the next page's limit and offset to <see cref="Query"/>.
+        /// </summary>
+        /// <returns>The query configured for the next page.</returns>
         public Query NextQuery()
         {
             return this.Query.ForPage(Page + 1, PerPage);
         }
 
+        /// <summary>
+        /// Executes the query for the next page.
+        /// </summary>
+        /// <param name="transaction">The transaction to use, or <see langword="null"/> for none.</param>
+        /// <param name="timeout">The command timeout in seconds, or <see langword="null"/> to use the configured default.</param>
+        /// <returns>The next page of results.</returns>
         public PaginationResult<T> Next(IDbTransaction transaction = null, int? timeout = null)
         {
             return this.Query.Paginate<T>(Page + 1, PerPage, transaction, timeout);
         }
 
+        /// <summary>
+        /// Asynchronously executes the query for the next page.
+        /// </summary>
+        /// <param name="transaction">The transaction to use, or <see langword="null"/> for none.</param>
+        /// <param name="timeout">The command timeout in seconds, or <see langword="null"/> to use the configured default.</param>
+        /// <param name="cancellationToken">The token used to cancel the operation.</param>
+        /// <returns>A task containing the next page of results.</returns>
         public async Task<PaginationResult<T>> NextAsync(IDbTransaction transaction = null, int? timeout = null, CancellationToken cancellationToken = default)
         {
             return await this.Query.PaginateAsync<T>(Page + 1, PerPage, transaction, timeout, cancellationToken);
         }
 
+        /// <summary>
+        /// Applies the previous page's limit and offset to <see cref="Query"/>.
+        /// </summary>
+        /// <returns>The query configured for the previous page.</returns>
         public Query PreviousQuery()
         {
             return this.Query.ForPage(Page - 1, PerPage);
         }
 
+        /// <summary>
+        /// Executes the query for the previous page.
+        /// </summary>
+        /// <param name="transaction">The transaction to use, or <see langword="null"/> for none.</param>
+        /// <param name="timeout">The command timeout in seconds, or <see langword="null"/> to use the configured default.</param>
+        /// <returns>The previous page of results.</returns>
         public PaginationResult<T> Previous(IDbTransaction transaction = null, int? timeout = null)
         {
             return this.Query.Paginate<T>(Page - 1, PerPage, transaction, timeout);
         }
 
+        /// <summary>
+        /// Asynchronously executes the query for the previous page.
+        /// </summary>
+        /// <param name="transaction">The transaction to use, or <see langword="null"/> for none.</param>
+        /// <param name="timeout">The command timeout in seconds, or <see langword="null"/> to use the configured default.</param>
+        /// <param name="cancellationToken">The token used to cancel the operation.</param>
+        /// <returns>A task containing the previous page of results.</returns>
         public async Task<PaginationResult<T>> PreviousAsync(IDbTransaction transaction = null, int? timeout = null, CancellationToken cancellationToken = default)
         {
             return await this.Query.PaginateAsync<T>(Page - 1, PerPage, transaction, timeout, cancellationToken);
         }
 
+        /// <summary>
+        /// Gets an iterator that starts with this page and loads each remaining page.
+        /// </summary>
         public PaginationIterator<T> Each
         {
             get