Possible to pass format specifier for an argument as another argument to String.Format?

For instance, let's say I have the DateTime format-string in a string variable, is there any syntax or method in .NET that would let me do the equivalent of this invalid code:

String line = String.Format("{0:{1}}", DateTime.Now, dateTimeFormat);
                   开发者_StackOverflow中文版             ^^^                        ^
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                                 +-- this would use this --+

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I think this syntax overview pretty much excludes dynamic parameters.

You will have to use a 2 stage system somehow, either pre-formatting your Date or by generating a format string. But I think both will be worse than the problem.

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What's wrong with just

string line = DateTime.Now.ToString(dateTimeFormat);

?