public override void ItemAdding(SPItemEventProperties properties)
{
    SPWeb TargetWeb = properties.OpenWeb();

    //SPListItem item = properties.ListItem; <------ ERROR
    //SPFile document = item.File; <------ ERROR
}

//get the url for the file name
 string fileName = properties.AfterUrl;
 //split it when it gets to /
 string[] nFileName = url.Split('/')
 //return only the file name
 fileName = nFileName[1];

//Files
string itemName = properties.Web.GetFile(properties.AfterUrl).Name;

//Folders
string itemName = properties.Web.GetFolder(properties.AfterUrl).Name;

properties.AfterProperties["Internal Name of the column"];