String to enum

[useo]

Hi,

does anyone know how I can cast a string to an enum which also
contains strings? For example:

enum MyENUM : string {

x = "123"
y = "456"
z = "789"

}

...

string myString = X;
to!(MyENUM)(myString); //  Error: cannot implicitly convert
expression (_adDupT((& D12TypeInfo_Aya6__initZ),s)) of char[]...
cast(MyENUM) myString; // Does work, but it seems that other values
like MyENUM.a, MyENUM.b... are also successfully casted to MyENUM but
MyENUM doesn't contain a, b or similiar invalid/undefined values.

I hope anyone can solve the problem... thanks.