[英]Reflection set value of a properties property
我有2节课:
public class CustomerViewModel {
public SystemViewModel system { get;set; }
}
public class SystemViewModel {
public bool isReadOnly { get; set; }
}
在方法控制器操作上,我具有一个自定义过滤器属性,该属性执行一些代码并确定用户是否具有ReadOnly或Write访问权限。 该属性可以应用于多个控制器上的多个动作。
到目前为止,使用反射我可以使用以下方式访问模型:
var viewModel = filterContext.Controller.ViewData.Model;
我无法将此模型转换为CustomerViewModel,因为在其他操作上,它可能类似于SalaryViewModel。 我所知道的是,任何需要readonly属性的模型都将具有SystemViewModel属性。
从我的自定义过滤器中,我需要一种能够更改readonly值的方法。
到目前为止,我有这个:
public override void OnActionExecuted(ActionExecutedContext filterContext) {
var viewModel = filterContext.Controller.ViewData.Model;
var systemViewModelPropertyInfo = model.GetType()
.GetProperties()
.FirstOrDefault(p => p.PropertyType == typeof(SystemViewModel));
if (systemViewModelPropertyInfo != null) {
// Up to here, everything works, systemViewModelPropertyInfo is of
// type PropertyInfo, and the systemViewModelPropertyInfo.PropertyType
// shows the SystemViewModel type
// If we get here, the model has the system property
// Here I need to try and set the IsReadOnly property to true/false;
// This is where I need help please
}
}
已解决感谢所有参与解决此问题的人。 特别感谢JuliánUrbano提供我一直在寻找的解决方案。 这是我从过滤器中得到的代码:
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
try
{
var viewModel = filterContext.Controller.ViewData.Model;
var systemViewModelPropertyInfoCount = viewModel.GetType().GetProperties().Count(p => p.PropertyType == typeof(SystemViewModel));
if(systemViewModelPropertyInfoCount == 1)
{
var systemViewModelPropertyInfo = viewModel.GetType().GetProperties().First(p => p.PropertyType == typeof(SystemViewModel));
if(systemViewModelPropertyInfo != null)
{
var systemViewModel = systemViewModelPropertyInfo.GetValue(viewModel, null) as SystemViewModel;
if(systemViewModel != null)
{
var admin = GetAdmin(filterContext.HttpContext.User.Identity.Name);
if(admin != null && _adminService.HasPermission(admin, _privilege, Access.Level.ReadWrite))
systemViewModel.ReadOnly = false;
else
systemViewModel.ReadOnly = true;
}
}
} else if(systemViewModelPropertyInfoCount > 1)
{
throw new Exception("Only once instance of type SystemViewModel allowed");
}
}
catch (Exception exception)
{
Log.Error(MethodBase.GetCurrentMethod(), exception);
filterContext.Controller.TempData["ErrorMessage"] = string.Format("Technical error occurred");
filterContext.Result = new RedirectResult("/Error/Index");
}
finally
{
base.OnActionExecuted(filterContext);
}
}
我无法将此模型转换为CustomerViewModel,因为在其他操作上,它可能类似于SalaryViewModel。 我所知道的是,任何需要readonly属性的模型都将具有SystemViewModel属性。
选项1
在我看来,最好的选择是编写一个像这样的接口:
public interface IWithSystemViewModel {
SystemViewModel System {get;}
}
并从您的类中实现它,就像:
public class CustomerViewModel : IWithSystemViewModel{
public SystemViewModel System { get;set; }
}
public class SalaryViewModel : IWithSystemViewModel{
public SystemViewModel System { get;set; }
}
因此您可以投射它并访问isReadOnly
属性:
IWithSystemViewModel viewModel = filterContext.Controller.ViewData.Model as IWithSystemViewModel;
if(viewModel!=null){
viewModel.System.isReadOnly ...
}
选项2
如果您想坚持使用反射:
var viewModel = filterContext.Controller.ViewData.Model;
SystemViewModel theSystem = viewModel.GetType().GetProperty("system")
.GetValue(viewModel, null) as SystemViewModel;
theSystem.isReadOnly ...
棘手的事情:在您的代码中,选择类型为SystemViewModel
的属性。 但是,如果该对象实际上具有您不知道的几个SystemViewModel
属性,该怎么办? 您确定要访问正确的地址吗? 您可以强制所有的用户使用相同的名称,但是再说一遍,就像使用上面选项1中的接口一样。
我肯定会选择选项1。
var viewModel = new CustomerViewModel();
var systemViewModelPropertyInfo = viewModel.GetType()
.GetProperties()
.FirstOrDefault(p => p.PropertyType == typeof(SystemViewModel));
if (systemViewModelPropertyInfo != null) {
var systemViewModelProperty = systemViewModelPropertyInfo.GetValue(viewModel, null) as SystemViewModel;
// get the desired value of isReadOnly here...
var isReadOnly = false;
// here, systemViewModelProperty may be null if it has not been set.
// You can decide what to do in that case. If you need a value to be
// present, you'll have to do something like this...
if (systemViewModelProperty == null) {
systemViewModelPropertyInfo.SetValue(viewModel, new SystemViewModel { isReadOnly = isReadOnly }, null);
}
else {
systemViewModelProperty.isReadOnly = isReadOnly;
}
}
也就是说,如果您实现了一个界面,则整个过程可能会更容易...
public interface IHaveSystemViewModel {
SystemViewModel system { get; set; }
}
var model = viewModel as IHaveSystemViewModel;
if (model != null) {
// again, you need to make sure you actually have a reference here...
var system = model.system ?? (model.system = new SystemViewModel());
system.isReadOnly = false; // or true
}
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