SharePoint - programmatically add list items can't set ID

I need to create new list item in sharepoint 2016 but while creating, on ID field, i'm getting this error: "This field cannot be updated". I'm not updating anything and i checked the list and it was empty too. I left this field empty and it has 0 value by defualt like when i'm inserting new row in sql tables.

The ID field is a system field which will increase automatically when new item created, so no need to set ID field value, here is a code snippet which add new item with default Title field and ID field will be automatically generated with 1 as it is a empty list previously:

            SPSite site = new SPSite("http://demoaam.contoso2016.com/sites/dev");
            using (SPWeb web=site.OpenWeb() )
            {
                SPList list = web.Lists["TestList"];
                SPListItem newitem = list.AddItem();
                newitem["Title"] = "NewItemTitle";
                newitem.Update();

            }