List<string> strlist = new List<string> { "one","two", "three" };
string somevalue = "two";
var result = strlist.Exists(e2 => e2 == somevalue);
如何将最后一个语句Exists()转换为表达式树?
你可以create an expression tree from a lambda expression,然后将其编译成一个函数,然后可以使用strlist
和somevalue
参数调用,如下所示:
var strlist = new List<string> { "one", "two", "three" };
var somevalue = "two";
Expression<Func<List<string>, string, bool>> expression = (list, value) =>
list.Exists(item => item == value);
Func<List<string>, string, bool> exists = expression.Compile();
bool result = exists(strlist, somevalue);
或者你可以在一行中完成所有这些,但它有点难以阅读:
var exists = ((Expression<Func<List<string>, string, bool>>)
((list, value) => list.Exists(item => item == value))).Compile();
但最后,做到这一点并不简单:
bool result = strlist.Contains(somevalue);