String.Format is not working properly

Question

I have below code :

private string Do2Decimal(string value)
{
    return String.Format("{0:0.##}", value);
}

Here I am passing string value as 16.32222.
What I know is, above code should format my value to 16.32.
But it is showing output value as 16.32222.

What mistake I am doing here??

Update : I have values in string format that is : "16.32222".
Sorry forgot to mention before.

Answer 1

Because you are passing it a string value. The formatting would work for floating point numbers / decimals. Just parse the number to either decimal / double type depending on your requirement like:

String.Format("{0:0.##}", decimal.Parse(value));

You can also use decimal.TryParse (or TryParse) family method for safer parsing. You can also modify your method to receive decimal/double type parameter and then apply the formatting. It would convey a better intent, IMO.

If your string has . as NumberDecimalSeparator and your culture doesn't support . as NumberDecimalSeparator then you can pass CultureInfo.InvariantCulture while parsing like:

string value = "16.322222";
string formattedString = String.Format("{0:0.##}", decimal.Parse(value, CultureInfo.InvariantCulture));