如何在动态条件的linq查询中使用order by子句？

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        string sortingField = "FieldName";
        bool ascending = true;

        var query = from item in dbContext.TableName
                    select item;

        if (ascending)
        {
            query = query.OrderBy(GetSortExpression(sortingField));
        }
        else
        {
            query = query.OrderByDescending(GetSortExpression(sortingField));
        }

        var results = query.ToList();

        // 处理排序后的结果
        // ...
    }

    static Func<DataItem, object> GetSortExpression(string fieldName)
    {
        switch (fieldName)
        {
            case "FieldName1":
                return item => item.FieldName1;
            case "FieldName2":
                return item => item.FieldName2;
            // 可以根据需要添加更多的排序字段
            default:
                return item => item.FieldName;
        }
    }
}