Asp.net Core调用GetProperty传ViewBag参数报RuntimeBinderException问题

• 核心错误是ViewBag是dynamic动态类型，Type.GetProperty()方法要求传入string类型的参数，直接传动态类型参数时，运行时绑定无法匹配到正确的方法重载，所以抛出RuntimeBinderException。
• 另外你的代码存在两处逻辑错误：
  1. 默认排序分支连续两次给ViewBag.SortField赋值，第二次直接把枚举值SortDirection.Ascending赋给了ViewBag.SortField，直接把排序字段覆盖成了枚举值，就算做类型转换也会获取不到属性。
  2. 非默认排序的else分支缺少大括号，只有第一行逻辑受else控制，ViewBag.SortField = sortField会无条件执行。

方案1：强制转换动态类型参数（快速修复） #

把用到ViewBag值的地方都转成对应类型，同时修复逻辑错误即可：

private List<Employee> SortEmployees(List<Employee> employees, String sortField, string currentSortField, SortDirection sortDirection)
{
    if (string.IsNullOrEmpty(sortField))
    {
        ViewBag.SortField = "EmployeeNumber";
        // 修复笔误：给SortDirection赋值而非覆盖SortField
        ViewBag.SortDirection = SortDirection.Ascending;
    }
    else
    {
        // 补全大括号避免逻辑错误
        if (currentSortField == sortField)
        {
            ViewBag.SortDirection = sortDirection == SortDirection.Ascending ? SortDirection.Descending : SortDirection.Ascending;
        }
        else
        {
            ViewBag.SortDirection = SortDirection.Ascending;
        }
        ViewBag.SortField = sortField;
    }

    // 将dynamic类型的ViewBag.SortField强制转成string传入
    var propertyInfo = typeof(Employee).GetProperty((string)ViewBag.SortField);
    // 排序方向判断也做强制转换
    if ((SortDirection)ViewBag.SortDirection == SortDirection.Ascending)
    {
        employees = employees.OrderBy(e => propertyInfo.GetValue(e, null)).ToList();
    }
    else
    {
        employees = employees.OrderByDescending(e => propertyInfo.GetValue(e, null)).ToList();
    }

    return employees;
}

方案2：直接用方法入参处理排序（更推荐） #

SortEmployees方法本身已经传入了强类型的sortField和sortDirection参数，排序逻辑完全可以直接用这两个参数，不需要依赖动态类型的ViewBag，从根源避免动态类型绑定错误，同时增加空校验兼容非法字段输入：

private List<Employee> SortEmployees(List<Employee> employees, string sortField, string currentSortField, SortDirection sortDirection)
{
    // 用局部强类型变量存储排序规则，避免依赖dynamic
    string finalSortField = nameof(Employee.EmployeeNumber);
    SortDirection finalSortDir = SortDirection.Ascending;

    if (!string.IsNullOrEmpty(sortField))
    {
        finalSortField = sortField;
        finalSortDir = currentSortField == sortField 
            ? (sortDirection == SortDirection.Ascending ? SortDirection.Descending : SortDirection.Ascending) 
            : SortDirection.Ascending;
    }

    // ViewBag只负责给视图传值，不参与业务逻辑计算
    ViewBag.SortField = finalSortField;
    ViewBag.SortDirection = finalSortDir;

    // 直接用强类型变量获取属性，加空校验避免非法字段报错
    var propertyInfo = typeof(Employee).GetProperty(finalSortField) 
        ?? typeof(Employee).GetProperty(nameof(Employee.EmployeeNumber));
    
    employees = finalSortDir == SortDirection.Ascending 
        ? employees.OrderBy(e => propertyInfo.GetValue(e, null)).ToList() 
        : employees.OrderByDescending(e => propertyInfo.GetValue(e, null)).ToList();

    return employees;
}

内容的提问来源于stack exchange，提问作者ha33