Cannot assign null to an implicitly-typed variable

Question

According to Visual Studio this is not ok:

var foo = null;

But this is ok:

var foo = false ? (double?)null : null;
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Answer 1

Because compiler cannot predict the type of null. Null can be assigned to any nullable datatype also to any reference type variable. So for implicit conversion, you have to cast null to some specific type.

var dt = (DateTime?)null; // This is correct
var dt1 = null; // This will throw compile time error.