我基本上是在尝试
this
但是我不知道会是什么,所以我用反射树和表达树来构建事物。
// Input (I don't know about "Book")
Type itemType = typeof(Book);
// Actual Code
// Build up func p => p.AuthorName == "Jon Skeet"
ParameterExpression predParam = Expression.Parameter(itemType, "p");
Expression left = Expression.Field(predParam, itemType.GetField("AuthorName"));
Expression right = Expression.Constant("Jon Skeet", typeof(string));
Expression equality = Expression.Equal(left, right);
Delegate myDelegate = Expression.Lambda(equality, new ParameterExpression[] { predParam }).Compile(); // Not sure if I need this
// Build up predicate type (Predicate<Book>)
Type genericPredicateType = typeof(Predicate<>);
Type constructedPredicateType = genericPredicateType.MakeGenericType(new Type[] { itemType });
// I need an instance to use this predicate, right? (** This Fails **)
object predicateInstance = Activator.CreateInstance(constructedPredicateType, new object[] { myDelegate });
基本上,我有一个
List<Book>
,我正试图思考的是,
Invoke
它的
Find
方法。这个
发现
方法需要
Predicate<Book>
而不是
Func<Book, bool>
我在这上面打了几个小时。
编辑:以下是错误跟踪的第一部分:
System.MissingMethodException: Constructor on type 'System.Predicate`1[[MyProject.Book, MyProject, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' not found.
