try

Webshop.Application/Services/Admin/IAdminSupplierService.cs

@@ -0,0 +1,16 @@
+// src/Webshop.Application/Services/Admin/IAdminSupplierService.cs
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Webshop.Application.DTOs; // SupplierDto
+
+namespace Webshop.Application.Services.Admin
+{
+    public interface IAdminSupplierService
+    {
+        Task<IEnumerable<SupplierDto>> GetAllSuppliersAsync();
+        Task<SupplierDto?> GetSupplierByIdAsync(Guid id);
+        Task<SupplierDto> CreateSupplierAsync(SupplierDto supplierDto);
+        // Task<bool> UpdateSupplierAsync(SupplierDto supplierDto); // Beispiel für zukünftige Methode
+        // Task<bool> DeleteSupplierAsync(Guid id); // Beispiel für zukünftige Methode
+    }
+}