What meens this part of the guide
Next we need to set some properties in the code behind. We need to check to see if an “id” parameter was passed in the query string. This will determine whether or not the control display an update or create
form. If an id was passed to the page, we will set the EntityId property on the EntityEditor control.
string id = Request.QueryString["id"];
oppEditor.EntityId = new Guid(id);
We will also need to set the EntityName property on the EntityGrid control.
oppEditor.EntityName = EntityName.opportunity.ToString();