Double.ToString Method in C#

The Double.ToString() method in C# is used to convert the numeric value of this instance to its equivalent string representation. This method provides several overloads to format the double value in different ways, including culture-specific formatting and custom format strings.

Syntax

Following is the syntax for the basic ToString() method −

public override string ToString();

Following is the syntax for ToString() with format specifier −

public string ToString(string format);

Following is the syntax for ToString() with culture-specific formatting −

public string ToString(IFormatProvider provider);

Return Value

The method returns a string that represents the value of the current Double instance.

Using Basic ToString() Method

Example

using System;
public class Demo {
   public static void Main() {
      double d1 = 45.7878d;
      double d2 = -68.89d;
      string str1 = d1.ToString();
      string str2 = d2.ToString();
      Console.WriteLine("Positive number: " + str1);
      Console.WriteLine("Negative number: " + str2);
   }
}

The output of the above code is −

Positive number: 45.7878
Negative number: -68.89

Using ToString() with Format Specifiers

Example

using System;
public class Demo {
   public static void Main() {
      double d = 1234.5678d;
      Console.WriteLine("Default: " + d.ToString());
      Console.WriteLine("Fixed-point (F2): " + d.ToString("F2"));
      Console.WriteLine("Currency (C): " + d.ToString("C"));
      Console.WriteLine("Scientific (E): " + d.ToString("E"));
      Console.WriteLine("Percentage (P): " + (0.85).ToString("P"));
   }
}

The output of the above code is −

Default: 1234.5678
Fixed-point (F2): 1234.57
Currency (C): $1,234.57
Scientific (E): 1.234568E+003
Percentage (P): 85.00%

Using ToString() with Culture-Specific Formatting

Example

using System;
using System.Globalization;
public class Demo {
   public static void Main() {
      double price = 1299.99d;
      CultureInfo usCulture = new CultureInfo("en-US");
      CultureInfo germanCulture = new CultureInfo("de-DE");
      Console.WriteLine("US format: " + price.ToString("C", usCulture));
      Console.WriteLine("German format: " + price.ToString("C", germanCulture));
      Console.WriteLine("Invariant culture: " + price.ToString(CultureInfo.InvariantCulture));
   }
}

The output of the above code is −

US format: $1,299.99
German format: 1.299,99 ?
Invariant culture: 1299.99

Common Format Specifiers

Conclusion

The Double.ToString() method provides flexible string conversion with support for various format specifiers and culture-specific formatting. Use format specifiers like "F2" for fixed decimal places, "C" for currency, or "E" for scientific notation to control the output format according to your application's needs.