Important thing

SecureSharing.Data/Migrations/20220929095405_Init.cs

                         name: "FK_FileModel_Messages_MessageId",
                         column: x => x.MessageId,
                         principalTable: "Messages",
-                        principalColumn: "Id");
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
                 });
 
             migrationBuilder.CreateIndex(