Linq to objects Predicate Builder

Question

使用linq到对象(不是linq到sql)进行条件查询的最佳方法是什么.

目前我正在使用http://www.albahari.com/nutshell/predicatebuilder.aspx中的Predicate构建器 ,并将已编译的谓词传递给IEnumerable.Where,它似乎工作得很好.

我要解决的示例代码:

我有这个

 string keyword1 = "Test1";
 string keyword2 = "Test3";

        IEnumerable<TestObject> tests = new List<TestObject>()
                                     {
                                         new TestObject() {Name1 = "Test1", Name2 = "Test1"},
                                         new TestObject() {Name1 = "Test2", Name2 = "Test2"},
                                         new TestObject() {Name1 = "Test3", Name2 = "Test3"},

                                     };

        if (!String.IsNullOrEmpty(keyword1) && String.IsNullOrEmpty(keyword2))
            tests = tests.Where(e => e.Name1.Contains(keyword1));
        else if (!String.IsNullOrEmpty(keyword2) && !String.IsNullOrEmpty(keyword1))
            tests = tests.Where(e => e.Name2.Contains(keyword2) || e.Name1.Contains(keyword1));

        return tests.ToList();

Answer 1

只需更改PredicateBuilder为使用委托而不是表达式树并使用lambdas来构建结果:

public static class DelegatePredicateBuilder
{
  public static Func<T, bool> True<T>()  { return f => true;  }
  public static Func<T, bool> False<T>() { return f => false; }

  public static Func<T, bool> Or<T>(this Func<T, bool> expr1,
                                     Func<T, bool> expr2)
  {
      return t => expr1(t) || expr2(t);
  }

  public static Func<T, bool> And<T>(this Func<T, bool> expr1,
                                     Func<T, bool> expr2)
  {
      return t => expr1(t) && expr2(t);
  }
}