Csharp/CSharp Tutorial/String/String Format

Formatting Using the R Format Specifier

class MainClass
{
  static void Main()
  {
    const double number = 1.612;
    double result;
    string text;
    text = string.Format("{0}", number);
    result = double.Parse(text);
    System.Console.WriteLine("{0}: result != number",result != number);
    text = string.Format("{0:R}", number);
    result = double.Parse(text);
    System.Console.WriteLine("{0}: result == number",result == number);
  }
}

.NET String Format Characters

String Format Character             Meaning in Life
C or c                              format currency. 
D or d                              format decimal numbers.
E or e                              Used for exponential notation.
F or f                              Used for fixed-point formatting.
G or g                              Stands for general. 
N or n                              numerical formatting.
X or x                              hexadecimal formatting.

String and WriteLine Format Specifiers

Character          Interpretation
C or c             Currency
D or d             Decimal
E or e             Exponent
F or f             Fixed point
G or g             General
N or n             Number; similar to F with the addition of comma thousand separators
P or p             Percentage
R or r             Round-trip 
X or x             Hex

String format: {0,3:D}, {1,8:D}

using System;  
  
class MainClass {  
  public static void Main() {  
    int sum = 0, prod = 1;
    for(int i=1; i <= 10; i++) { 
      sum += i; 
      prod *= i; 
      string str = String.Format("Sum:{0,3:D}  Product:{1,8:D}", 
                          sum, prod); 
      Console.WriteLine(str); 
    } 
  } 
}

Sum:  1  Product:       1
Sum:  3  Product:       2
Sum:  6  Product:       6
Sum: 10  Product:      24
Sum: 15  Product:     120
Sum: 21  Product:     720
Sum: 28  Product:    5040
Sum: 36  Product:   40320
Sum: 45  Product:  362880
Sum: 55  Product: 3628800

String format: {0:C}

using System;

class MainClass
{
  public static void Main(string[] args)
  {
    string formStr = null;
    formStr = string.Format("you had {0:C} in your account?", 99989.987);
    Console.WriteLine(formStr);    
  }
}

you had $99,989.99 in your account?

Use String.Format() to format a value.

using System;  
  
class MainClass {  
  public static void Main() {
    double v = 17688.65849;
    double v2 = 0.15;
    int x = 21;
    string str = String.Format("{0:F2}", v);  
    Console.WriteLine(str);  
    str = String.Format("{0:N5}", v);  
    Console.WriteLine(str);  
  
    str = String.Format("{0:e}", v);  
    Console.WriteLine(str);  
  
    str = String.Format("{0:r}", v);  
    Console.WriteLine(str);  
  
    str = String.Format("{0:p}", v2);  
    Console.WriteLine(str);  
  
    str = String.Format("{0:X}", x);  
    Console.WriteLine(str);  
    str = String.Format("{0:D12}", x);
    Console.WriteLine(str);  
    str = String.Format("{0:C}", 189.99);
    Console.WriteLine(str);
  }
}

17688.66
17,688.65849
1.768866e+004
17688.65849
15.00 %
15
000000000021
$189.99

Use ToString to format double: C

using System; 
 
class MainClass { 
  public static void Main() { 
    string str = 189.99.ToString("C"); 
    Console.WriteLine(str); 
  }
}

$189.99