Formatting Math.Pow Output

Question

I hate to ask such a dumb question, but I'm just starting out, so here goes.

myString = "2 to 2.5 power is " + Math.Pow(2, 2.5);

I want to format the resulting number to 4 decimal places and show the string in a MessageBox. I can't seem to figure this out or find the answer in the book. Thanks!

Answer 1

The ToString method should do the trick. You might need to look it up in the MSDN to find more formatting options.

Math.Pow(2, 2.5).ToString("N4")

Answer 2

To show a string in a MessageBox you use MessageBox.Show . In particular, there is an overload accepting a single string parameter that will be displayed in the MessageBox . Thus, we need

string s = // our formatted string
MessageBox.Show(s);

Now, let's figure out what our string is. A useful method here is String.Format . A useful reference here is the Standard Numeric Format Strings page on MSDN. In particular, I draw your attention to the fixed-point specifier "F" or "f" :

The fixed-point ("F) format specifier converts a number to a string of the form "-ddd.ddd…" where each "d" indicates a digit (0-9). The string starts with a minus sign if the number is negative.

The precision specifier indicates the desired number of decimal places.

Thus, we want

double result = Math.Pow(2, 2.5);
string s = String.Format("2 to 2.5 power is {0:F4}", result);

so, putting it all together,

double result = Math.Pow(2, 2.5);
string s = String.Format("2 to 2.5 power is {0:F4}", result);
MessageBox.Show(s);

Answer 3

string.format("2 to 2.5 power is {0:0.000}", Math.Pow(2, 2.5));

Answer 4

Math.Pow(2, 2.5).ToString("N4") 

is what you want I think.

more formatting options

Answer 5

这不是一个愚蠢的问题：其他几个答案都是错误的。

MessageBox.Show(string.Format("2 to 2.5 power is {0:F4}", Math.Pow(2, 2.5)));