Linq PredicateBuilder-多个OR [英] Linq PredicateBuilder - Multiple ORs

问题描述

我正在尝试使用PredicateBuilder，如此处所述- http://www. albahari.com/nutshell/predicatebuilder.aspx

I'm trying to use the PredicateBuilder, as described here - http://www.albahari.com/nutshell/predicatebuilder.aspx

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;

根据示例，

据我所见应该起作用

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;

但是我得到的只是

错误1方法的类型参数 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable， System.Func)'不能为 从用法推断.尝试 指定类型参数

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.

我试图在LINQ的在职"知识上有所了解，如果这是一个简单的问题，请您道歉.

I'm trying to gain some understanding in LINQ 'on-the-job', so apologies if this is a simple question.

推荐答案

Ah;您的列表使用的是IEnumerable<T>扩展方法(而不是IQueryable<T>)-尝试:

Ah; your list is using IEnumerable<T> extension methods (rather than IQueryable<T>) - try:

var streetList = from street in streetData.AsQueryable().Where(predicate)
                 select street;

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