пожалуй ошибся не я

VeterinaryView/VeterinaryBusinessLogic/BusinessLogic/VisitLogic.cs

@@ -93,12 +93,12 @@ namespace VeterinaryBusinessLogic.BusinessLogic
 			{
 				throw new ArgumentNullException("Нет названия визита", nameof(model.VisitName));
 			}
-			if (model.DateVisit != null)
+			if (model.DateVisit == null)
 			{
 				throw new ArgumentNullException("Нет времени визита",
 			   nameof(model.DateVisit));
 			}
-			if (model.DateVisit >= DateTime.Now)
+			if (model.DateVisit <= DateTime.Now)
 			{
 				throw new ArgumentNullException("Дата посещения не должна быть в прошлом", nameof(model.DateVisit));
 			}

VeterinaryView/VeterinaryDatabaseImplement/Implements/PetStorage.cs

@@ -19,13 +19,10 @@ namespace VeterinaryDatabaseImplement.Implements
 		}
 		public List<PetViewModel> GetFilteredList(PetSearchModel model)
 		{
-			if (string.IsNullOrEmpty(model.PetName))
-			{
-				return new();
-			}
+
 			using var context = new VeterinaryDatabase();
 			return context.Pets.Where(x => x.OwnerId == model.OwnerId)
-			.Where(x => x.PetName.Contains(model.PetName))
+			.Where(x => String.IsNullOrEmpty(model.PetName) || x.PetName.Contains(model.PetName))
 		   .Select(x => x.GetViewModel)
 		   .ToList();
 		}
@@ -103,8 +100,7 @@ namespace VeterinaryDatabaseImplement.Implements
 		public PetViewModel? Update(PetBindingModel model)
 		{
 			using var context = new VeterinaryDatabase();
-			var component = context.Pets.FirstOrDefault(x => x.Id ==
-		   model.Id);
+			var component = context.Pets.FirstOrDefault(x => x.Id ==model.Id);
 			if (component == null)
 			{
 				return null;

VeterinaryView/VeterinaryShowOwnerApp/Views/Home/CreateVisit.cshtml

@@ -15,7 +15,7 @@
 	<div class="row">
 		<div class="col-4">Дата:</div>
 		<div class="col-8">
-			<input type="datetime" id="datetime" name="date" />
+			<input type="datetime-local" id="datetime" name="datetime" />
 		</div>
 	</div>
 	<div class="row">

VeterinaryView/VeterinaryShowOwnerApp/Views/Home/UpdatePet.cshtml

@@ -29,6 +29,11 @@
 		<div class="col-8"><input type="text" id="gender" name="gender" class="form-control" /></div>
 	</div>
 
+	<div class="row">
+		<div class="col-8"></div>
+		<div class="col-4"><input type="submit" value="Сохранить" class="btn btn-primary" /></div>
+	</div>
+
 </form>
 
 @section Scripts