Cosmos: Escape invalid characters in the id value

src/EFCore.Cosmos/ValueGeneration/Internal/IdValueGenerator.cs

@@ -87,20 +87,42 @@ private void AppendString(StringBuilder builder, object? propertyValue)
             switch (propertyValue)
             {
                 case string stringValue:
-                    builder.Append(stringValue.Replace("|", "^|"));
+                    AppendEscape(builder, stringValue);
                     return;
                 case IEnumerable enumerable:
                     foreach (var item in enumerable)
                     {
-                        builder.Append(item.ToString()!.Replace("|", "^|"));
+                        AppendEscape(builder, item.ToString()!);
                         builder.Append('|');
                     }
 
+                    return;
+                case DateTime dateTime:
+                    AppendEscape(builder, dateTime.ToString("O"));
                     return;
                 default:
-                    builder.Append(propertyValue == null ? "null" : propertyValue.ToString()!.Replace("|", "^|"));
+                    if (propertyValue == null)
+                    {
+                        builder.Append("null");
+                    } else
+                    {
+                        AppendEscape(builder, propertyValue.ToString()!);
+                    }
                     return;
             }
         }
+
+        private static StringBuilder AppendEscape(StringBuilder builder, string stringValue)
+        {
+            var startingIndex = builder.Length;
+            return builder.Append(stringValue)
+                // We need this to avoid collissions with the value separator
+                .Replace("|", "^|", startingIndex, builder.Length - startingIndex)
+                // These are invalid characters, see https://docs.microsoft.com/en-us/dotnet/api/microsoft.azure.documents.resource.id
+                .Replace("/", "^2F", startingIndex, builder.Length - startingIndex)
+                .Replace("\\", "^5C", startingIndex, builder.Length - startingIndex)
+                .Replace("?", "^3F", startingIndex, builder.Length - startingIndex)
+                .Replace("#", "^23", startingIndex, builder.Length - startingIndex);
+        }
     }
 }

test/EFCore.Cosmos.FunctionalTests/EndToEndCosmosTest.cs

@@ -456,6 +456,59 @@ public async Task Can_add_update_delete_end_to_end_with_Guid_async()
             }
         }
 
+        [ConditionalFact]
+        public async Task Can_add_update_delete_end_to_end_with_DateTime_async()
+        {
+            var options = Fixture.CreateOptions();
+
+            var customer = new CustomerDateTime
+            {
+                Id = DateTime.MinValue,
+                Name = "Theon/\\#\\\\?",
+                PartitionKey = 42
+            };
+
+            using (var context = new CustomerContextDateTime(options))
+            {
+                await context.Database.EnsureCreatedAsync();
+
+                var entry = context.Add(customer);
+
+                Assert.Equal("CustomerDateTime|0001-01-01T00:00:00.0000000|Theon^2F^5C^23^5C^5C^3F", entry.CurrentValues["__id"]);
+
+                await context.SaveChangesAsync();
+            }
+
+            using (var context = new CustomerContextDateTime(options))
+            {
+                var customerFromStore = await context.Set<CustomerDateTime>().SingleAsync();
+
+                Assert.Equal(customer.Id, customerFromStore.Id);
+                Assert.Equal("Theon/\\#\\\\?", customerFromStore.Name);
+
+                customerFromStore.Value = 23;
+
+                await context.SaveChangesAsync();
+            }
+
+            using (var context = new CustomerContextDateTime(options))
+            {
+                var customerFromStore = await context.Set<CustomerDateTime>().SingleAsync();
+
+                Assert.Equal(customer.Id, customerFromStore.Id);
+                Assert.Equal(23, customerFromStore.Value);
+
+                context.Remove(customerFromStore);
+
+                await context.SaveChangesAsync();
+            }
+
+            using (var context = new CustomerContextDateTime(options))
+            {
+                Assert.Empty(await context.Set<CustomerDateTime>().ToListAsync());
+            }
+        }
+
         private class Customer
         {
             public int Id { get; set; }
@@ -477,6 +530,14 @@ private class CustomerGuid
             public int PartitionKey { get; set; }
         }
 
+        private class CustomerDateTime
+        {
+            public DateTime Id { get; set; }
+            public string Name { get; set; }
+            public int PartitionKey { get; set; }
+            public int Value { get; set; }
+        }
+
         private class CustomerNoPartitionKey
         {
             public int Id { get; set; }
@@ -515,6 +576,26 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
             }
         }
 
+        private class CustomerContextDateTime : DbContext
+        {
+            public CustomerContextDateTime(DbContextOptions dbContextOptions)
+                : base(dbContextOptions)
+            {
+            }
+
+            protected override void OnModelCreating(ModelBuilder modelBuilder)
+            {
+                modelBuilder.Entity<CustomerDateTime>(
+                    cb =>
+                    {
+                        cb.Property(c => c.Id);
+                        cb.Property(c => c.PartitionKey).HasConversion<string>();
+                        cb.HasPartitionKey(c => c.PartitionKey);
+                        cb.HasKey(c => new { c.Id, c.Name });
+                    });
+            }
+        }
+
         [ConditionalFact]
         public async Task Can_add_update_delete_with_collections()
         {