How to specify total number of character in C# number formatting?

Is there a way to specify total number of characters when formatting doubles?

Lets say I have 0.00012345678开发者_JS百科, and I specify total number of characters (7), I want to get 1.23e-4. Format "G7" would give 1.2345e-4.

More examples:

0.00000012345678F -> 1.23e-7 
0.00012345678F    -> 1.23e-4 
0.12345678F       -> 1.23e-1 
1.2345678F        -> 1.23457 
12.345678F        -> 12.3457
12345678F         -> 1.234e8

You probably want to use the "e" format string like so...

String.Format("{0:0.00e+0}", number);

You have a misunderstanding about the meaning of "precision". For a floating point number, "precision" means the number of significant digits, so the result returned by "G6" is correct.

If you want a fixed number of characters, use a custom format string like Jason suggested.

{0:00e+0}

http://blog.stevex.net/string-formatting-in-csharp/