LastOrDefault

zzzprojects · Apr 9, 2024 · 9f074d0 · 9f074d0
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diff --git a/src/System.Linq.Dynamic.Core.NewtonsoftJson/NewtonsoftJsonExtensions.cs b/src/System.Linq.Dynamic.Core.NewtonsoftJson/NewtonsoftJsonExtensions.cs
@@ -419,6 +419,51 @@ public static JToken Last(this JArray source, LambdaExpression lambda)
     }
     #endregion Last
 
+    #region LastOrDefault
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JArray"/> to return the last element of.</param>
+    /// <param name="config">The <see cref="NewtonsoftJsonParsingConfig"/>.</param>
+    /// <param name="predicate">A function to test each element for a condition.</param>
+    /// <param name="args">An object array that contains zero or more objects to insert into the predicate as parameters. Similar to the way String.Format formats strings.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JToken? LastOrDefault(this JArray source, NewtonsoftJsonParsingConfig config, string predicate, params object?[] args)
+    {
+        Check.NotNull(source);
+        Check.NotNull(config);
+
+        var queryable = ToQueryable(source);
+        return ToJToken(queryable.LastOrDefault(predicate, args));
+    }
+
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JArray"/> to return the last element of.</param>
+    /// <param name="predicate">A function to test each element for a condition.</param>
+    /// <param name="args">An object array that contains zero or more objects to insert into the predicate as parameters. Similar to the way String.Format formats strings.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JToken? LastOrDefault(this JArray source, string predicate, params object?[] args)
+    {
+        return LastOrDefault(source, NewtonsoftJsonParsingConfig.Default, predicate, args);
+    }
+
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JArray"/> to return the last element of.</param>
+    /// <param name="lambda">A cached Lambda Expression.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JToken? LastOrDefault(this JArray source, LambdaExpression lambda)
+    {
+        Check.NotNull(source);
+
+        var queryable = ToQueryable(source);
+        return ToJToken(queryable.LastOrDefault(lambda));
+    }
+    #endregion LastOrDefault
+
     #region Select
     /// <summary>
     /// Projects each element of a sequence into a new form.

diff --git a/src/System.Linq.Dynamic.Core.SystemTextJson/SystemTextJsonExtensions.cs b/src/System.Linq.Dynamic.Core.SystemTextJson/SystemTextJsonExtensions.cs
@@ -500,6 +500,64 @@ public static JsonElement Last(this JsonDocument source, LambdaExpression lambda
     }
     #endregion Last
 
+    #region LastOrDefault
+    /// <summary>
+    /// Returns the last element of a sequence, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JsonDocument"/> to return the last element of.</param>
+    /// <returns>default if source is empty; otherwise, the last element in source.</returns>
+    public static JsonElement? LastOrDefault(this JsonDocument source)
+    {
+        Check.NotNull(source);
+
+        var queryable = ToQueryable(source);
+        return ToJsonElement(queryable.LastOrDefault());
+    }
+
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JsonDocument"/> to return the last element of.</param>
+    /// <param name="config">The <see cref="SystemTextJsonParsingConfig"/>.</param>
+    /// <param name="predicate">A function to test each element for a condition.</param>
+    /// <param name="args">An object array that contains zero or more objects to insert into the predicate as parameters. Similar to the way String.Format formats strings.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JsonElement? LastOrDefault(this JsonDocument source, SystemTextJsonParsingConfig config, string predicate, params object?[] args)
+    {
+        Check.NotNull(source);
+        Check.NotNull(config);
+
+        var queryable = ToQueryable(source);
+        return ToJsonElement(queryable.LastOrDefault(predicate, args));
+    }
+
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JsonDocument"/> to return the last element of.</param>
+    /// <param name="predicate">A function to test each element for a condition.</param>
+    /// <param name="args">An object array that contains zero or more objects to insert into the predicate as parameters. Similar to the way String.Format formats strings.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JsonElement? LastOrDefault(this JsonDocument source, string predicate, params object?[] args)
+    {
+        return LastOrDefault(source, SystemTextJsonParsingConfig.Default, predicate, args);
+    }
+
+    /// <summary>
+    /// Returns the last element of a sequence that satisfies a specified condition, or a default value if the sequence contains no elements.
+    /// </summary>
+    /// <param name="source">The <see cref="JsonDocument"/> to return the last element of.</param>
+    /// <param name="lambda">A cached Lambda Expression.</param>
+    /// <returns>The first element in source that passes the test in predicate.</returns>
+    public static JsonElement? LastOrDefault(this JsonDocument source, LambdaExpression lambda)
+    {
+        Check.NotNull(source);
+
+        var queryable = ToQueryable(source);
+        return ToJsonElement(queryable.LastOrDefault(lambda));
+    }
+    #endregion LastOrDefault
+
     #region Select
     /// <summary>
     /// Projects each element of a sequence into a new form.

diff --git a/test/System.Linq.Dynamic.Core.NewtonsoftJson.Tests/NewtonsoftJsonTests.cs b/test/System.Linq.Dynamic.Core.NewtonsoftJson.Tests/NewtonsoftJsonTests.cs
@@ -140,6 +140,16 @@ public void Last()
         ((string?)_source.First("Age > 30")["Name"]).Should().Be("Doe");
     }
 
+    [Fact]
+    public void LastOrDefault()
+    {
+        // Act + Assert 1
+        ((string?)_source.LastOrDefault("Age > 0")!["Name"]).Should().Be("Doe");
+
+        // Act + Assert 2
+        _source.LastOrDefault("Age > 999").Should().BeNull();
+    }
+
     [Fact]
     public void Select()
     {

diff --git a/test/System.Linq.Dynamic.Core.SystemTextJson.Tests/SystemTextJsonTests.cs b/test/System.Linq.Dynamic.Core.SystemTextJson.Tests/SystemTextJsonTests.cs
@@ -149,6 +149,19 @@ public void Last()
         _source.Last("Age > 0").GetRawText().Should().BeEquivalentTo(JsonDocument.Parse(@"{""Name"":""Doe"",""Age"":40}").RootElement.GetRawText());
     }
 
+    [Fact]
+    public void LastOrDefault()
+    {
+        // Act + Assert 1
+        _source.LastOrDefault()!.Value.GetRawText().Should().BeEquivalentTo(JsonDocument.Parse(@"{""Name"":""Doe"",""Age"":40}").RootElement.GetRawText());
+
+        // Act + Assert 2
+        _source.LastOrDefault("Age > 0")!.Value.GetRawText().Should().BeEquivalentTo(JsonDocument.Parse(@"{""Name"":""Doe"",""Age"":40}").RootElement.GetRawText());
+
+        // Act + Assert 3
+        _source.LastOrDefault("Age > 999").Should().BeNull();
+    }
+
     [Fact]
     public void Select()
     {