C# Linq PredicateBuilder - 多个 OR
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Linq PredicateBuilder - Multiple ORs
提问by Duncan
I'm trying to use the PredicateBuilder, as described here - http://www.albahari.com/nutshell/predicatebuilder.aspx
我正在尝试使用 PredicateBuilder，如下所述 - http://www.albahari.com/nutshell/predicatebuilder.aspx
The following code
以下代码
var predicate = PredicateBuilder.False<StreetDTO>();
predicate = predicate.Or(p => p.Locality.Contains(criteria.Locality));
predicate = predicate.Or(p => p.Name.Contains(criteria.Name));
predicate = predicate.Or(p => p.Town.Contains(criteria.Town));
List<StreetDTO> streetData = StreetData.Instance();
var streetList = from street in streetData.Where(predicate)
select street;
as far as I see this shouldwork, according to the example
根据示例，据我所知，这应该有效
var newKids = Product.ContainsInDescription ("BlackBerry", "iPhone");
var classics = Product.ContainsInDescription ("Nokia", "Ericsson")
.And (Product.IsSelling());
var query =
from p in Data.Products.Where (newKids.Or (classics))
select p;
but all I get is
但我得到的只是
Error 1 The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
错误 1 无法从用法推断方法“System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)”的类型参数。尝试明确指定类型参数。
I'm trying to gain some understanding in LINQ 'on-the-job', so apologies if this is a simple question.
我试图在 LINQ 'on-the-job' 中获得一些理解，所以如果这是一个简单的问题，我很抱歉。
采纳答案by Marc Gravell
Ah; your list is using IEnumerable<T>extension methods (rather than IQueryable<T>) - try:
啊; 您的列表正在使用IEnumerable<T>扩展方法（而不是IQueryable<T>） - 尝试：
var streetList = from street in streetData.AsQueryable().Where(predicate)
select street;
回答by bruno conde
Try compiling your predicate:
尝试编译您的谓词：
var streetList = from street in streetData.Where(predicate.Compile())
select street;
