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Hi I have this code using generic and nullable: // The first one is for class public static TResult With<TInput, TResult>(this TInput o, Func<TInput, TResult> evaluator) where TResult : class where TInput : class // The second one is for struct (Nullable) public static TResult With<TInput, TResult>(this Nullable<TInput> o, Func<TInput, TResult> evaluator) where TResult : class where TInput : struct Please note the TInput constraint, one is class, the other one is struct. Then I use them in: string s; int? i; // ... s.With(o => ""); i.With(o => ""); // Ambiguos method It cause an Ambiguos error. But I also have the another pair: public static TResult Return<TInput, TResult>(this TInput o, Func<TInput, TResult> evaluator, TResult failureValue) where TInput : class public static TResult Return<TInput, TResult>(this Nullable<TInput> o, Func<TInput, TResult> evaluator, TResult failureValue) where TInput : struct This one compiles successfully string s; int? i; // ... s.Return(o => 1, 0); i.Return(o => i + 1, 0); I got no clues why this happen. The first one seems Ok, but compiles error. The second one ('Return') should be error if the first one is, but compiles successfully. Did I miss something?

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