.net core 反射特性使用，反射通过特性匹配需要的字段赋值

有这样一个需求，数据库查询出来是这样的数据

要根据tag来获取数据给字段赋值，这种情况一般是使用行专列处理后在前台显示，但是我们这里需求有点特殊，也不太好使用行专列来处理。如果直接写死代码的话就是这个样子

var tagCountListAll = BaseDal.Db.Queryable<StuElevateAssignment>().
        Where(a => classIdlist.Contains(a.ClassId) && a.DAStatus != 1 && a.ASSType == _params.ASSType && a.CreateTime >= _params.dateTime && a.CreateTime < nextDay)
        .GroupBy(a => new { a.Tag, a.ClassId }).Select(a => new
        {
            ClassId = a.ClassId,
            Tag = a.Tag,
            Count = SqlFunc.AggregateCount(a.Tag),
        }).ToList();
foreach (VClassTeam item in vClassTeams)
{
    var tagCountList = tagCountListAll.Where(a => a.ClassId == item.ID).ToList();
    ClassStatisticsShowStyleDto classStatisticsDto = new ClassStatisticsShowStyleDto();
    classStatisticsDto.ClassId = item.ID;
    classStatisticsDto.ClassName = item.ClassName;
    if (tagCountList.First(a => a.Tag == "plank") == null)
    {
        classStatisticsDto.PlankCount = "/";
    }
    else
    {
        classStatisticsDto.PlankCount = tagCountList.First(a => a.Tag == "plank").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "仰卧起坐") == null)
    {
        classStatisticsDto.SitUpsCount = "/";
    }
    else
    {
        classStatisticsDto.SitUpsCount = tagCountList.First(a => a.Tag == "仰卧起坐").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "俯卧撑") == null)
    {
        classStatisticsDto.PushUpCount = "/";
    }
    else
    {
        classStatisticsDto.PushUpCount = tagCountList.First(a => a.Tag == "俯卧撑").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "健身房锻炼") == null)
    {
        classStatisticsDto.GymExerciseCount = "/";
    }
    else
    {
        classStatisticsDto.GymExerciseCount = tagCountList.First(a => a.Tag == "健身房锻炼").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "其它") == null)
    {
        classStatisticsDto.OtherCount = "/";
    }
    else
    {
        classStatisticsDto.OtherCount = tagCountList.First(a => a.Tag == "其它").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "球类运动") == null)
    {
        classStatisticsDto.BallCount = "/";
    }
    else
    {
        classStatisticsDto.BallCount = tagCountList.First(a => a.Tag == "球类运动").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "田径类") == null)
    {
        classStatisticsDto.TrackCount = "/";
    }
    else
    {
        classStatisticsDto.TrackCount = tagCountList.First(a => a.Tag == "田径类").Count + "";
    }
    if (tagCountList.First(a => a.Tag == "跳绳") == null)
    {
        classStatisticsDto.RopeSkippingCount = "/";
    }
    else
    {
        classStatisticsDto.RopeSkippingCount = tagCountList.First(a => a.Tag == "跳绳").Count + "";
    }
    classStatisticsDtoList.Add(classStatisticsDto);
}

这种代码写起来就太不灵活了，太硬编码了，而且我们这里类型还不止这些，这样写的话代码会写得超级长，很难受，如果这里的类型有做数据字典的情况还会，用这里的tag和数据字典的字段匹配实体的属性名，用来反射给实体的属性赋值就行了，但是这里设计数据库的太坑了，数据字典也没有，所以我们只能想其他方法了，这里就可以考虑用特性来做一个映射，然后在使用反射。

配置特性，其实就是让中文的tag和字段做一个映射，有了这个映射就可以使用反射来赋值了

public class ClassStatisticsShowStyleDto
{
    public string ClassName { get; set; }
    public string ClassId { get; set; }
    [DisplayName("plank")]
    public string PlankCount { get; set; }
    [DisplayName("仰卧起坐")]
    public string SitUpsCount { get; set; }
    [DisplayName("俯卧撑")]
    public string PushUpCount { get; set; }
    [DisplayName("跳绳")]
    public string RopeSkippingCount { get; set; }
    [DisplayName("田径类")]
    public string TrackCount { get; set; }
    [DisplayName("球类运动")]
    public string BallCount { get; set; }
    [DisplayName("健身房锻炼")]
    public string GymExerciseCount { get; set; }
    [DisplayName("其它")]
    public string OtherCount { get; set; }
}

有了这个映射就可以使用反射来赋值了:

var tagCountListAll = BaseDal.Db.Queryable<StuElevateAssignment>().
        Where(a => classIdlist.Contains(a.ClassId) && a.DAStatus != 1 && a.ASSType == _params.ASSType && a.CreateTime >= _params.dateTime && a.CreateTime < nextDay)
        .GroupBy(a => new { a.Tag, a.ClassId }).Select(a => new
        {
            ClassId = a.ClassId,
            Tag = a.Tag,
            Count = SqlFunc.AggregateCount(a.Tag),
        }).ToList();
foreach (VClassTeam item in vClassTeams)
{
    var tagCountList = tagCountListAll.Where(a => a.ClassId == item.ID).ToList();
    ClassStatisticsShowStyleDto classStatisticsDto = new ClassStatisticsShowStyleDto();
    classStatisticsDto.ClassId = item.ID;
    classStatisticsDto.ClassName = item.ClassName;
    // 反射获取所有属性。用反射来代替下面的写死数据查询
    PropertyInfo[] properties = classStatisticsDto.GetType().GetProperties();
    foreach (PropertyInfo propertyInfo in properties)
    {
        var attrs = propertyInfo.GetCustomAttributes(typeof(DisplayNameAttribute), true);
        if (attrs != null)
        {
            if (attrs.Length > 0)
            {
                var displayName = ((DisplayNameAttribute)attrs[0]).DisplayName;
                // 用特性来找到需要的数据在赋值
                if (!string.IsNullOrWhiteSpace(displayName))
                {
                    if (tagCountList.FirstOrDefault(a => a.Tag == displayName) == null)
                    {
                        //classStatisticsDto.PlankCount = "/";
                        propertyInfo.SetValue(classStatisticsDto, "/");
                    }
                    else
                    {
                        //classStatisticsDto.PlankCount = tagCountList.First(a => a.Tag == displayName).Count + "";
                        propertyInfo.SetValue(classStatisticsDto, tagCountList.First(a => a.Tag == displayName).Count + "");
                    }
                }
            }
        }
    }
}