[英]Using 'Any' on IEnumerable<string> in OData LINQ query
我使用Microsoft.Data.Odata
(5.6)運行以下查詢:
IEnumerable<Service> services = context.Services.Expand(ServiceQueryExpansion)
.Where(c =>
(serviceNames.Any(s => s.Equals(
c.ServiceName, StringComparison.OrdinalIgnoreCase))))
serviceNames是IEnumerable的字符串
嘗試上述查詢時出現以下錯誤:
Error translating Linq expression to URI: The source parameter for the 'Any' method has to be either a navigation or a collection property.
我該如何解決這個問題?
我知道這很有趣也很令人興奮(諷刺)但你可以像這樣動態構建你的Where表達式:
var serviceNames = new string[] { "SERVICE1","SERVICE2"};
Expression<Func<Service,bool>> inList = v => false;
var parameter = inList.Parameters[0];
var propertyExpression = Expression.Property(parameter,"ServiceName");
foreach (var serviceName in serviceNames)
{
var body = inList.Body;
var constantExpression = Expression.Constant(serviceName);
var equalityExpression = Expression.Equal(propertyExpression,constantExpression);
body = Expression.OrElse(body,equalityExpression);
inList = Expression.Lambda<Func<Service, bool>>(body, parameter);
}
IEnumerable<Service> services = context.Services.Expand(ServiceQueryExpansion)
.Where(inList);
此方法從列表中構建一個自定義where子句,它類似於(v => v.ServiceName ==“Service1”|| v.ServiceName ==“Service2”|| v.ServiceName ==“Service3”)
您可以按照我的博客http://coding.grax.com/2013/07/filter-pattern-for-linq-query-filter.html中的說明將此邏輯封裝到自定義“WhereContains(yourListHere)”自定義中過濾擴展方法。
你可以寫:
var services = context.Services.Expand(ServiceQueryExpansion).AsEnumerable()
.Where(c => serviceNames.Contains(c.ServiceName));
但它將下載整個服務集合。 要么:
var services = serviceNames.SelectMany(s=>
context.Services.Expand(ServiceQueryExpansion).Where(c=> c.ServicaName == s));
這將創建N個請求。
我不知道在Linq到OData的任何更好的方法。
我所做的是應用我可以使用的過濾器,然后列出,然后在本地獲得結果后再制作另一個過濾器。
var services = context.Services.Expand(ServiceQueryExpansion).ToList();
services = services.Where(s => serviceNames.Any(n => n.ServiceName.Equals(s, StringComparison.OrdinalIgnoreCase)));
如果您有多條記錄不需要通過網絡,這不是最佳選擇。
另一種選擇是創建數據服務操作。
[WebGet]
public IQueryable<Service> GetServicesByServiceName(string serviceNames)
{
var serviceNamesArray = serviceNames.Split(',');
var ctx = YourContext();
return ctx.Services.Include("ServiceQueryExpansion").Where(s => serviceNamesArrays.Any(n => s.ServiceName.Equals(n, StringComparison.OrdinalIgnoreCase))).AsQueryable();
}
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