所以我想做的是使用表达式树将谓词应用于集合中的每个值(读取映射或 list.All(predicate))。看来我没有获得绑定(bind)到 All 提供的值的谓词的输入参数,我有点卡住了。这是我正在使用的代码(使用 linqpad)::
public class SomeType
{
public IEnumerable<bool> Collection { get; set; }
}
void Main()
{
var list = new SomeType {
Collection = new List<bool> { true, true, true }
};
var functor = Compiler((SomeType t) => t.Collection, (bool x) => x);
functor(list).Dump();
}
MethodInfo FindMethod<TInput>(Type location, string name)
{
var handle = location
.GetMethods(BindingFlags.Static | BindingFlags.Public)
.Where(method => method.Name == name).First();
return handle.MakeGenericMethod(typeof(TInput));
}
Predicate<TObject> Compiler<TObject, TProperty>(
Expression<Func<TObject, IEnumerable<TProperty>>> selector,
Expression<Predicate<TProperty>> predicate)
{
var query = FindMethod<TProperty>(typeof(Enumerable), "All");
var expression = Expression.Call(query,
new Expression[] {
Expression.Invoke(selector, selector.Parameters),
Expression.Lambda<Func<TProperty, bool>>(predicate.Body,
Expression.Parameter(typeof(TProperty))),
});
return Expression.Lambda<Predicate<TObject>>(expression,
selector.Parameters).Compile();
}
如果这个问题在另一个问题中得到了回答(我找了一会儿),则表示感谢和抱歉。
最佳答案
这确实有效,但我必须更改 Predicate<TObject>
至 Func<TObject, bool>
.如果您愿意,我可以尝试将其改回。
static Predicate<TObject> Compiler<TObject, TProperty>(
Expression<Func<TObject, IEnumerable<TProperty>>> selector,
Expression<Func<TProperty, bool>> predicate)
{
var query = FindMethod<TProperty>(typeof(Enumerable), "All");
var expression = Expression.Call(
query,
Expression.Invoke(selector, selector.Parameters),
predicate);
return Expression
.Lambda<Predicate<TObject>>(expression, selector.Parameters)
.Compile();
}
5 分钟后...如果你真的想使用 Predicate<TObject>
...
static Predicate<TObject> Compiler<TObject, TProperty>(
Expression<Func<TObject, IEnumerable<TProperty>>> selector,
Expression<Predicate<TProperty>> predicate)
{
var query = FindMethod<TProperty>(typeof(Enumerable), "All");
var predicateAsFunc = Expression.Lambda<Func<TProperty, bool>>(
predicate.Body,
predicate.Parameters);
var expression = Expression.Call(
query,
Expression.Invoke(selector, selector.Parameters),
predicateAsFunc);
return Expression
.Lambda<Predicate<TObject>>(expression, selector.Parameters)
.Compile();
}
关于C# 表达式树绑定(bind),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7759346/