使用C#将数据表转换为分层数据结构(JSON)

Question

我正在对datatable执行SQL查询.查询可以返回多个列.结果是键值格式并表示分层数据.请参见下面的屏幕截图

图像显示3个部分.首先是数据,然后是数据的层次表示和JSON等价物.

目前图像显示4级数据,但我们可以有6-7级数据.格式将保持不变,但列数可以更改.

如何使用C#获得所需的结果？？我知道这是基本的编程,但我很难用它.

Answer 1

使用您在示例中显示的固定级别层次结构,可以使用带分组的LINQ查询来生成JSON的树结构.以下是三级层次结构的示例:

static void Main(string[] args)
{
    var data = new List<Data>
    {
        new Data("Food", "1_g", "beverage", "2_b", "hot", "3_h"),
        new Data("Food", "1_g", "beverage", "2_b", "cold", "3_c"),
        new Data("Food", "1_g", "fruit", "2_f", "juicy", "3_j"),
        new Data("Food", "1_g", "fruit", "2_f", "solid", "3_s"),
        new Data("Food", "1_g", "cookie", "2_c", "chocolate", "3_cho"),
    };

    var tree = from l1 in data
                group l1 by new { key = l1.Key_L1, name = l1.L1 } into group1
                select new
                {
                    key = group1.Key.key,
                    name = group1.Key.name,
                    children = from l2 in group1
                                group l2 by new { key = l2.Key_L2, name = l2.L2 } into group2
                                select new
                                {
                                    key = group2.Key.key,
                                    name = group2.Key.name,
                                    children = from l3 in group2
                                                select new { key = l3.Key_L3, name = l3.L3 }
                                }
                };

    var serializer = new JavaScriptSerializer();
    Console.WriteLine(serializer.Serialize(tree));
    Console.ReadLine();
}

class Data
{
    public Data(string l1, string k1, string l2, string k2, string l3, string k3)
    {
        L1 = l1; Key_L1 = k1;
        L2 = l2; Key_L2 = k2;
        L3 = l3; Key_L3 = k3;
    }
    public string L1 { get; set; }
    public string Key_L1 { get; set; }
    public string L2 { get; set; }
    public string Key_L2 { get; set; }
    public string L3 { get; set; }
    public string Key_L3 { get; set; }
}

以上是使用POCO的技术的工作示例.

你提到"数据表"; 我假设这是指.NET DataTable类？如果是这样,您可以使用LINQ来查询DataTable.您只需要使用DataSetExtensions将其转换为可枚举.请参阅:DataTable上的LINQ查询

然后在LINQ语句中,将列表替换为数据表.AsEnumerable()并将属性引用替换为.Field<string>("").像这样:

DataTable dt = // load data table
var tree = from l1 in dt.AsEnumerable()
           group l1 by new { key = l1.Field<string>("Key_L1"), name = l1.Field<string>("L1") } into group1
           select new
           {
               // etc.
           };

对于可变数量的列,您必须使用递归方法,如下所示:

var tree = Descend(dt.AsEnumerable(), 1, 3);

private static System.Collections.IEnumerable Descend(IEnumerable<DataRow> data, int currentLevel, int maxLevel)
{
    if (currentLevel > maxLevel)
    {
        return Enumerable.Empty<object>();
    }
    return from item in data
            group item by new
            {
                key = item.Field<string>("Key_L" + currentLevel),
                name = item.Field<string>("L" + currentLevel)
            } into rowGroup
            select new
            {
                key = rowGroup.Key.key,
                name = rowGroup.Key.name,
                children = Descend(rowGroup, currentLevel + 1, maxLevel)
            };
}

需要注意的一点是,这种方法children在叶节点上创建了一个空集合.