diff --git a/Polyclinic/PolyclinicBusinessLogic/BusinessLogics/DiagnoseLogic.cs b/Polyclinic/PolyclinicBusinessLogic/BusinessLogics/DiagnoseLogic.cs
index b791a09..80bd0db 100644
--- a/Polyclinic/PolyclinicBusinessLogic/BusinessLogics/DiagnoseLogic.cs
+++ b/Polyclinic/PolyclinicBusinessLogic/BusinessLogics/DiagnoseLogic.cs
@@ -58,14 +58,14 @@ namespace PolyclinicBusinessLogic.BusinessLogics
             return element;
         }
 
-        public List<DiagnoseViewModel>? ReadList(DiagnoseSearchModel? model)
+        public List<DiagnoseViewModel> ReadList(DiagnoseSearchModel? model = null)
         {
             _logger.LogInformation("ReadList. Name:{Name} Id:{Id}, UserId:{UserId}", model?.Name, model?.Id, model?.UserId);
             var list = model == null ? _diagnoseStorage.GetFullList() : _diagnoseStorage.GetFilteredList(model);
             if (list == null)
             {
                 _logger.LogWarning("ReadList return null list");
-                return null;
+                return new List<DiagnoseViewModel>();
             }
             _logger.LogInformation("ReadList. Count:{Count}", list.Count);
             return list;
diff --git a/Polyclinic/PolyclinicContracts/BusinessLogicsContracts/IDiagnoseLogic.cs b/Polyclinic/PolyclinicContracts/BusinessLogicsContracts/IDiagnoseLogic.cs
index d931c6d..1b28ddc 100644
--- a/Polyclinic/PolyclinicContracts/BusinessLogicsContracts/IDiagnoseLogic.cs
+++ b/Polyclinic/PolyclinicContracts/BusinessLogicsContracts/IDiagnoseLogic.cs
@@ -6,7 +6,7 @@ namespace PolyclinicContracts.BusinessLogicsContracts
 {
     public interface IDiagnoseLogic
     {
-        List<DiagnoseViewModel>? ReadList(DiagnoseSearchModel? model);
+        List<DiagnoseViewModel> ReadList(DiagnoseSearchModel? model = null);
         DiagnoseViewModel? ReadElement(DiagnoseSearchModel model);
         bool Create(DiagnoseBindingModel model);
         bool Update(DiagnoseBindingModel model);
diff --git a/Polyclinic/PolyclinicWebAppImplementer/Controllers/DiagnosesController.cs b/Polyclinic/PolyclinicWebAppImplementer/Controllers/DiagnosesController.cs
index a332252..fe0a442 100644
--- a/Polyclinic/PolyclinicWebAppImplementer/Controllers/DiagnosesController.cs
+++ b/Polyclinic/PolyclinicWebAppImplementer/Controllers/DiagnosesController.cs
@@ -19,7 +19,7 @@ namespace PolyclinicWebAppImplementer.Controllers
         [HttpGet]
         public IActionResult Index()
         {
-            List<DiagnoseViewModel> diagnoses = _diagnoseLogic.ReadList(null);
+            List<DiagnoseViewModel> diagnoses = _diagnoseLogic.ReadList();
             if (diagnoses == null)
             {
                 diagnoses = new();