double? to decimal? conversion

Why after this code fragment:

 double? d = 123.4;
 decimal? dec = (decimal?)d; //dec is null

is dec's v开发者_StackOverflow中文版alue null?

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I've tested on .NET 2.0 and .NET 4.0, and I get dec as 123.4, as expected. Are you sure you don't perhaps have the break-point too high?

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dec isn't null, its 123.4

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I know this will point same thing. Your code gives me 123,4 as expected. It works fine.

I can just say try this :) but the result is same : 123,4

double? d = 123.4;
 decimal? dec = (decimal?)d.Value;

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My best guess is that the implicit conversion being called in the cast fails, leaving dec with a null value, rather than whatever truncated/rounded value you expect.

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It's not null. You must have an error elsewhere.