好吧,我不确定是否有更好的方法(因为这似乎是一个常见用例的大量工作),但这是我解决这个问题的方法。
我继承自QueryHelper
类来修改PostExecuteQuery
方法来执行委托。
public class ExtendedQueryHelper : QueryHelper
{
public ExtendedQueryHelperOptions Options { get; set; }
public ExtendedQueryHelper(ODataQuerySettings querySettings) : base(querySettings)
{}
public override IEnumerable PostExecuteQuery(IEnumerable queryResult)
{
if (Options != null && Options.PostExecuteQueryHandler != null)
{
return Options.PostExecuteQueryHandler(queryResult);
}
return base.PostExecuteQuery(queryResult);
}
}
委托是在一个名为的类中定义的ExtendedQueryHelperOptions
public class ExtendedQueryHelperOptions
{
private const string EXTENDED_QUERY_HELPER_OPTIONS_KEY = "EXTENDED_QUERY_HELPER_OPTIONS_KEY";
public delegate IEnumerable PostExecuteQueryDelegate(IEnumerable queryResult);
public PostExecuteQueryDelegate PostExecuteQueryHandler { get; set; }
public void InjectIntoRequest(HttpRequestMessage request)
{
request.Properties.Add(EXTENDED_QUERY_HELPER_OPTIONS_KEY, this);
}
public static ExtendedQueryHelperOptions GetFromRequest(HttpRequestMessage request)
{
object options;
request.Properties.TryGetValue(EXTENDED_QUERY_HELPER_OPTIONS_KEY, out options);
return (ExtendedQueryHelperOptions)options;
}
}
为了设置这些选项,我必须继承BreezeQueryableAttribute
并在以下情况下注入这些选项QueryHelper
正在创建:
public class ExtendedBreezeQueryableAttribute : BreezeQueryableAttribute
{
protected HttpRequestMessage Request { get; set; }
public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
{
Request = actionContext.Request;
base.OnActionExecuting(actionContext);
}
protected override QueryHelper NewQueryHelper()
{
var queryHelper = new ExtendedQueryHelper(GetODataQuerySettings());
queryHelper.Options = ExtendedQueryHelperOptions.GetFromRequest(Request);
return queryHelper;
}
}
现在我可以注入要在过滤结果上运行的代码,如下所示:
[BreezeController]
public class BreezeController : BaseController
{
//...
[HttpGet]
[ExtendedBreezeQueryable]
public IQueryable<Foo> Foos()
{
var options = new ExtendedQueryHelperOptions
{
PostExecuteQueryHandler = delegate(IEnumerable results) {
// This code will be run after the querying has been
// applied by Breeze
var foos = results.Cast<Foo>().ToList();
foreach (var foo in foos)
{
foo.ComputedProperty = ComputeSomething();
}
return foos;
}
};
// Inject these options into the Request, so the ExtendedBreezeQueryableAttribute
// can get to them later
options.InjectIntoRequest(Request);
return Db.Foos;
}
}