Linq first function support condition (#532)

* test to show a bug where First/FirstOrDefault doesn't work when it has a statement #530

* fix bug First/FirstOrDefault doesn't work when it has a statement #530

---------

Co-authored-by: SMAH1 <[email protected]>

Author: SMAH1

src/Redis.OM/Common/ExpressionTranslator.cs

@@ -228,6 +228,16 @@ internal static RedisQuery BuildQueryFromExpression(Expression expression, Type
                             case "First":
                             case "Any":
                             case "FirstOrDefault":
+                                if (exp.Arguments.Count > 1)
+                                {
+                                    // Combine Where clause with existing query
+                                    var condition = TranslateWhereMethod(exp, parameters, ref dialect);
+                                    query.QueryText = query.QueryText == "*" ?
+                                        condition :
+                                        $"({condition} {query.QueryText})";
+                                    query.Dialect = dialect;
+                                }
+
                                 query.Limit ??= new SearchLimit { Offset = 0 };
                                 query.Limit.Number = 1;
                                 break;

test/Redis.OM.Unit.Tests/RediSearchTests/SearchFunctionalTests.cs

@@ -128,6 +128,59 @@ public void TestFirstOrDefault()
             Assert.Equal("John", firstJohn.Name);
         }
 
+        [Fact]
+        public void TestFirstOrDefaultWithExpression()
+        {
+            var person = new Person[] {
+                new Person { Name = "Q1", Age = 110 },
+                new Person { Name = "Q2", Age = 112 },
+                new Person { Name = "Q3", Age = 115 },
+                new Person { Name = "Q1", Age = 120 },
+                new Person { Name = "Q2", Age = 122 },
+                new Person { Name = "Q1", Age = 130 },
+                new Person { Name = "Q2", Age = 132 },
+            };
+
+            var collection = new RedisCollection<Person>(_connection, 10000);
+            IQueryable<Person> query = collection;
+
+            foreach (var p in person)
+            {
+                collection.Insert(p);
+            }
+
+            var firstInCollection = collection.FirstOrDefault(x => x.Name == "Q3");
+            var firstInQuery = query.FirstOrDefault(x => x.Name == "Q3");
+
+            Assert.NotNull(firstInCollection);
+            Assert.NotNull(firstInQuery);
+
+            Assert.Equal("Q3", firstInCollection.Name);
+            Assert.Equal("Q3", firstInQuery.Name);
+
+            firstInCollection = collection.FirstOrDefault(x => x.Name == "Q2" && x.Age > 115);
+            firstInQuery = query.FirstOrDefault(x => x.Name == "Q2" && x.Age > 115);
+
+            Assert.NotNull(firstInCollection);
+            Assert.NotNull(firstInQuery);
+
+            Assert.Equal("Q2", firstInCollection.Name);
+            Assert.Equal("Q2", firstInQuery.Name);
+            Assert.Equal(122, firstInCollection.Age);
+            Assert.Equal(122, firstInQuery.Age);
+
+            firstInCollection = collection.Where(x => x.Age > 115).FirstOrDefault(x => x.Name == "Q1");
+            firstInQuery = query.Where(x => x.Age > 115).FirstOrDefault(x => x.Name == "Q1");
+
+            Assert.NotNull(firstInCollection);
+            Assert.NotNull(firstInQuery);
+
+            Assert.Equal("Q1", firstInCollection.Name);
+            Assert.Equal("Q1", firstInQuery.Name);
+            Assert.Equal(120, firstInCollection.Age);
+            Assert.Equal(120, firstInQuery.Age);
+        }
+
         [Fact]
         public void TestAny()
         {