Expression tree is an amazing feature of C#, however it only supports a limited subset of C# features.
While there is no native support to null propagation operator a?.b, this library can do the job as an expression visitor.
Just call Visit method of the visitor and you are done!
As well the ?. operator, the visitor evaluates its left-hand operand no more than once.
You can use projects like ReadableExpressions to check the expression returned by visitor.
Check some examples of use in unit tests
It works from the basic cenarios:
Expression<Func<string, int>> ex = str => str.Length;which become something like
(string str) =>
{
string caller = str;
return (caller == null) ? null : (int?)caller.Length;
}To the complex ones
Expression<Func<string, char>> ex = str => str == "foo" ? 'X' : Self(str).Length.ToString()[0];which become something like
(string str) => (str == "foo")
? (char?)'X'
: {
string caller =
{
int? caller =
{
string caller = Program.Self(str);
return (caller == null) ? null : (int?)caller.Length;
};
return (caller == null) ? null : ((int)caller).ToString();
};
return (caller == null) ? null : (char?)caller[0];
}