Additional fields Add, Update and Delete work (too well)

SelectableListView works when programmatically setting selection

ModernKeePass.Application/Entry/Commands/UpsertField/UpsertFieldCommand.cs

@@ -0,0 +1,30 @@
+using MediatR;
+using ModernKeePass.Application.Common.Interfaces;
+using ModernKeePass.Domain.Exceptions;
+
+namespace ModernKeePass.Application.Entry.Commands.UpsertField
+{
+    public class UpsertFieldCommand : IRequest
+    {
+        public string EntryId { get; set; }
+        public string FieldName { get; set; }
+        public object FieldValue { get; set; }
+
+        public class UpsertFieldCommandHandler : IRequestHandler<UpsertFieldCommand>
+        {
+            private readonly IDatabaseProxy _database;
+
+            public UpsertFieldCommandHandler(IDatabaseProxy database)
+            {
+                _database = database;
+            }
+
+            public void Handle(UpsertFieldCommand message)
+            {
+                if (!_database.IsOpen) throw new DatabaseClosedException();
+
+                _database.UpdateEntry(message.EntryId, message.FieldName, message.FieldValue);
+            }
+        }
+    }
+}