Whats wrong with setting nullable double to null?

Question

Possible Duplicates:
Why can't I set a nullable int to null in a ternary if statement?
Nullable types and the ternary operator. Why won't this work?

Whats wrong with the below

public double? Progress { get; set; }
Progress = null; // works
Progress = 1; // works
Progress = (1 == 2) ? 0.0 : null; // fails

Type of conditional expression cannot be determined because there is no implicit conversion between 'double' and '<null>'

Answer 1

When using the ?: operator, it has to resolve to a single type, or types that has an implicit conversion between them. In your case, it will either return a double or null, and double does not have an implicit conversion to null.

You will see that

Progress = (1 == 2) ? (double?)0.0 : null;

works fine, since there is an implicit conversion between nullable double and null

Answer 2

The double is 0.0 in this case

Progress = (1 == 2) ? (double?)0.0 : null; // works