String.Format method in C # enter the journal title

first, the definition
String.Format is the text equivalent of replacing each format item in the specified String type data with the value of the corresponding object.
Such as:

(1)
string P1 = "Jackie";
string P2 = "Aillo";
Response.Write (String.Format ("Hello {0}, I ' m {1}", p1, p2));
(2)
Response.Write (String.Format ("Hello {0}, I ' m {1}", "Jackie", "Aillo"));

The effect is the same. Replaces the first item's {0} and {1}, respectively, with the values of the last two items.
The result of the output is: Hello Jackie, I ' m Aillo

Second, the String.Format of the multi-format definition:
Here the so-called multi-format refers to a format item can be defined in each of the format parameters, each format parameter separated by a semicolon (;). The value of a format item with 2 and 3 format parameters must be of a numeric type in order to determine whether it is negative, positive, zero.
With 1 format parameters:

//output in the format of scientific notation
Double P1 = 1000000;
Response.Write (String.Format ("{0:e2}", p1));

With 2 format parameters:

/* When the format item corresponds to a non-negative value, select the first format; a negative number selects the second format */
Double P1 = 10000;
Double P2 =-2420.50;
Response.Write (String.Format ("{0:#,## #0.00;#,## #0.000;} <BR> ", p1));
Response.Write (String.Format ("{0:#,## #0.00;#,## #0;}", p2));

With 3 format parameters:

/

* Select the first format when the corresponding value for the format item is a positive number;
The negative number is the second medium format;
The value equals zero is the third format */
1double P1 = 10000;
Double P2 =-2420.50;
Double P3 = 0.00;
Response.Write (String.Format ("{0:#,## #0.00;#,## #0.000;#,## #0 .0000}<br>", p1));
Response.Write (String.Format ("{0:#,## #0.00;#,## #0.000;#,## #0 .0000}<br>", p3));
Response.Write (String.Format ("{0:#,## #0.00;#,## #0.000;#,## #0.0000}", p2));

Add:
{0:N2}The N3,F3 in indicates the type of data after formatting and the number of decimal places. such as: N2 is a number with 2 decimals;
Similar to this:

N or n represents a number
F or f means fixed point
E or E means scientific notation.
D or D denotes decimal number
x or x indicates hexadecimal
G or G means regular
C or C denotes currency

Reprinted from: https://www.ezloo.com/2008/11/string_format.html

String.Format method in C # enter the journal title