c# - Implicit operator for int? -

i've learned use implicit operators classes.

now want this:

public static implicit operator string(int val) {     return "the value is: " + val.tostring(); // nonsense example } 

however wrong. compiler says:

user-defined conversion must convert or enclosing type

how can workaround this?

my goal able run code this:

int x = 50; textbox1.text = x; // without using .tostring() or casting 

you can't add operator outside of class of either parameter or return type of operator.
in other words: can't add operator converts between 2 types both don't control.

the compiler error explicit this:

user-defined conversion must convert or enclosing type

so, trying achieve here not possible.
best option extension method on int performs conversion , returns string.