How to format currency string in C# to add commas in thousands place?

You can format currency in C# using various methods, here are few

Using Standard Currency formatting in C#

decimal dec = 123.00M;
string ukCurrency = dec.ToString("C", new CultureInfo("en-GB")); // output -> "£123.00"
string usCurrency = dec.ToString("C", new CultureInfo("en-US")); // output -> "$123.00"

Here, "C" (or currency) format specifier converts a number to a string that represents a currency amount.

OR

double price = 1234.25;
string FormattedPrice = price.ToString("N");
//output
// 1,234.25

Here "N"  is used instead of "C".

OR

          var myPrice=110.1211;
		Console.WriteLine(myPrice.ToString("C2")) ;
        Console.WriteLine(myPrice.ToString("N2"));

//output
//$110.12
//110.12

The number after the C and N indicates upto how many decimals you need string formatted.

C formats the number as a currency string, which includes a currency symbol, default symbol is "$', you can use Culture Info as shown above for any other currency type.

OR

                decimal CurrencyAmount = 1000.39m;
		string moneyValue = String.Format("{0:C}", CurrencyAmount);
		
		Console.WriteLine("Formatted value: "+ moneyValue);

               //output : 
               //Formatted value: $1,000.39

OR 

If your Currency value is not a decimal value

string.Format("{0:#.00}", Convert.ToDecimal(CurrencyValue) / 100);

Hope it helps.

I would like to add my own version here, if your string is in Decimal/Double, then you can format it in Currency as below

using System;
					
public class Program
{
	public static void Main()
	{
		double amountInDouble = 1234.95;

		amountInDouble.ToString("C");// formats based on local PC

		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-ie")));    //  €1,234.95
		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("es-es")));    //  1.234,95 € 
		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-GB")));   //  £1,234.95 

		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-au")));    //  $1,234.95
		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-us")));    //  $1,234.95
		Console.WriteLine(amountInDouble.ToString("C", System.Globalization.CultureInfo.GetCultureInfo("en-ca")));   //  $1,234.95
	}
}

Here is the fiddle link https://dotnetfiddle.net/YCPEwh

Thanks