此版本是最基础版，不涉及上下月，上下年衔接。
首先确定数据格式

// 折线图
    Area: {
        categories: [],
        series: []
    }

配置数据模型

     public class Datalist { 
            public List<string> categories { get; set; }

            public List<DataDetail> series { get; set; }
        }

        public class DataDetail
        {
            public string name { get; set; }
            public int[] data { get; set; }

            public string color { get; set; }
        }

程序本体

     /// <summary>
        /// 小程序-获取charts数据
        /// </summary>
        [HttpGet("GetChartsDataByType")]
        [AllowAnonymous]
        public async Task<dynamic> GetChartsDataByType(int type)
        {
            var businessId = "zagwzq530";
            var data = new Datalist();
            //获取当前时间
            DateTime nowdate = DateTime.Now;
            var date = nowdate.Date;
            
            //通过传入的type决定获取的数据的范围，1为周，2为月，3为年
            switch (type)
            {
                case 1://根据周查看用户增长量
                    //限制为7位数的整数数组
                    //不需要额外填充数据，默认数组就是由7个0组成
                    int[] a = new int[7];
                    // 获取周几
                    DayOfWeek currentDayOfWeek = nowdate.DayOfWeek;
                    // 将周几转成数字
                    int dayOfWeek = (int)nowdate.DayOfWeek;

                    //动态计算前几日是分别是几号，获取各自的每天的数量
                        for (int i = 0; i < 6; i++) // 循环一周
                        {
                            var y = -dayOfWeek + i;
                            if (y <= 0) {
                                DateTime twoDaysAgo = nowdate.AddDays(y);
                                var date1 = twoDaysAgo.Date;
                                var entity = _db.Queryable<ArApp_UserEntity>().Where(a => a.CreatorTime.Value.Date == date1).Where(a => a.DeleteMark == null && a.BusinessId == businessId).Count();
                                a[i] = entity;
                            }

                        }
                    List<string> categories = new List<string>() { "周日", "周一", "周二", "周三", "周四", "周五", "周六" };
                    List<DataDetail> series = new List<DataDetail>() {new DataDetail() { name = "用户数", data= a, color = "#facc14" }};
                    data.categories = categories;
                    data.series = series;

                    break;

                case 2://根据月查看用户增长量
                    int[] b = new int[4];
                    //首先根据当前时间获取年，月
                    var year1 = nowdate.Year;
                    var mouth1 = nowdate.Month;
                    //获取所有今年这个月的数据
                    var entity1 = _db.Queryable<ArApp_UserEntity>().Where(a => a.CreatorTime.Value.Year == year1 && a.CreatorTime.Value.Month == mouth1).Where(a => a.DeleteMark == null && a.BusinessId == businessId).ToListAsync();
                    //循环获取所在周，因为就4个值，所以直接switch判断，
                    foreach (var item in entity1.Result) {
                        int weekOfYear = (int)item.CreatorTime.Value.DayOfWeek;
                        if (weekOfYear > 0 && weekOfYear < 5) {
                            switch (weekOfYear)
                            {
                                case 1:
                                    b[0] += 1;
                                    break;
                                case 2:
                                    b[1] += 1;
                                    break;
                                case 3:
                                    b[2] += 1;
                                    break;
                                case 4:
                                    b[3] += 1;
                                    break;
                            }
                        }
                    };
                    List<string> categories2 = new List<string>() { "第一周", "第二周", "第三周", "第四周"};
                    List<DataDetail> series2 = new List<DataDetail>() { new DataDetail() { name = "用户数", data = b, color = "#2fc25b" }};
                    data.categories = categories2;
                    data.series = series2;

                    break;

                case 3://根据年查看用户增长量
                    int[] c = new int[12];
                    //首先根据当前时间获取年，月
                    var year = nowdate.Year;
                    var mouth = nowdate.Month;
                    //先判断数据的年份是否一样
                    //在判断月份
                    for (int i = 1;i <= mouth;i++ ) {
                        //判断数据的年份是否一样,并且月份也要一样
                        var entity = _db.Queryable<ArApp_UserEntity>().Where(a => a.CreatorTime.Value.Year == year && a.CreatorTime.Value.Month == i).Where(a => a.DeleteMark == null && a.BusinessId == businessId).Count();
                        c[i-1] = entity;

                    };
                    List<string> categories3 = new List<string>() { "1月", "2月", "3月", "4月", "5月", "6月", "7月", "8月", "9月", "10月", "11月", "12月" };
                    List<DataDetail> series3 = new List<DataDetail>() { new DataDetail() { name = "用户数", data = c, color = "#1890ff" } };
                    data.categories = categories3;
                    data.series = series3;
                    break;

                default:

                    Console.WriteLine("Invalid number");
                    break;

            };
           
            return data;

        }