String format for Double in C#

Use the static method String.Format for form double string format in C#.

For three decimal places −

String.Format("{0:0.000}", 987.383); String.Format("{0:0.000}", 987.38); String.Format("{0:0.000}", 987.7899);

For thousands separator −

String.Format("{0:0,0.0}", 54567.46); String.Format("{0:0,0}", 54567.46);

To format string −

Example

using System; class Demo {    public static void Main(String[] args) {       Console.WriteLine("Three decimal places...");           Console.WriteLine( String.Format("{0:0.000}", 987.383));       Console.WriteLine( String.Format("{0:0.000}", 987.38));       Console.WriteLine(String.Format("{0:0.000}", 987.7899));           Console.WriteLine("Thousands Separator...");       Console.WriteLine(String.Format("{0:0,0.0}", 54567.46));       Console.WriteLine(String.Format("{0:0,0}", 54567.46));    } }