add tests

Author: ElizabethOkerio

test/Microsoft.AspNetCore.OData.Tests/Query/Expressions/SelectExpandBinderTest.cs

@@ -10,6 +10,7 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
@@ -356,6 +357,52 @@ public void Bind_UsingEFQueryProvider_LowerCamelCasedModel_GeneratedExpression__
             Assert.Null(innerInnerCustomer.Instance.Orders);
         }
 
+        [Fact]
+        public void Bind_SelectAndExpand_WithNullProperties_DoesNotThrowException()
+        {
+            // Arrange
+            IQueryable<User> users;
+            string expand = "FileRefNavigation";
+
+            User user = new User
+            {
+                UserId = 1,
+                Name = "Alex",
+                Age = 35,
+                DataFileRef = null,
+                FileRefNavigation = null
+            };
+
+            users = new[] { user }.AsQueryable();
+            ODataQueryContext context = new ODataQueryContext(_model, typeof(User)) { RequestContainer = new MockServiceProvider() };
+
+            SelectExpandQueryOption selectExpand = new SelectExpandQueryOption(select: null, expand: expand, context: context);
+
+            QueryBinderContext queryBinderContext = new QueryBinderContext(_model, _settings, selectExpand.Context.ElementClrType)
+            {
+                NavigationSource = context.NavigationSource
+            };
+
+            queryBinderContext.QueryProvider = HandleNullPropagationOptionHelper.EntityFrameworkQueryProviderNamespace;
+
+            // Act
+            SelectExpandBinder binder = new SelectExpandBinder();
+            IQueryable queryable = binder.ApplyBind(users, selectExpand.SelectExpandClause, queryBinderContext);
+
+            // Assert
+            Assert.NotNull(queryable);
+
+            IEnumerator enumerator = queryable.GetEnumerator();
+            Assert.True(enumerator.MoveNext());
+            var usr = Assert.IsAssignableFrom<SelectExpandWrapper<User>>(enumerator.Current);
+            Assert.False(enumerator.MoveNext());
+            Assert.NotNull(usr.Instance);
+            Assert.Equal("Microsoft.AspNetCore.OData.Tests.Query.Expressions.User", usr.Instance.GetType().ToString());
+            IEnumerable<SelectExpandWrapper<DataFile>> fileRefsNavigations = usr.Container
+                .ToDictionary(PropertyMapper)["FileRefNavigation"] as IEnumerable<SelectExpandWrapper<DataFile>>;
+            Assert.Null(fileRefsNavigations);
+        }
+
         [Fact]
         public void Bind_GeneratedExpression_CheckNullObjectWithinChainProjectionByKey()
         {
@@ -2095,6 +2142,7 @@ public static IEdmModel GetEdmModel()
             builder.EntitySet<QueryOrder>("Orders");
             builder.EntitySet<QueryCity>("Cities");
             builder.EntitySet<QueryProduct>("Products");
+            builder.EntitySet<User>("Users");
 
             customer.Collection.Function("IsUpgraded").Returns<bool>().Namespace="NS";
             customer.Collection.Action("UpgradeAll").Namespace = "NS";
@@ -2305,4 +2353,27 @@ public enum QueryColor
 
         Blue
     }
+
+    public class User
+    {
+        [Key]
+        public int UserId { get; set; }
+        [Required]
+        public string Name { get; set; }
+        [Required]
+        public int Age { get; set; }
+
+        //Navigations
+        [ForeignKey("FileRefNavigation")]
+        public int? DataFileRef { get; set; }
+        public DataFile? FileRefNavigation { get; set; }
+    }
+
+    public class DataFile
+    {
+        [Key]
+        public int FileId { get; set; }
+        [Required]
+        public string FileName { get; set; }
+    }
 }