Avoiding Scientific Notation When Converting Doubles to Strings in .NET

.NET developers often encounter challenges when converting double values to strings, particularly avoiding the scientific notation format. This article presents a robust and efficient solution.

Maintaining Decimal Precision

To accurately represent a wide range of double values, including very large or very small numbers, it's crucial to maintain sufficient decimal precision. Since double values can have exponents ranging from -308 to 308, potentially shifting the decimal point by up to 15 places, we need to accommodate a significant number of decimal places.

A Custom Number Format String

The following custom format string achieves the desired formatting, preserving up to 339 decimal places:

doubleFixedPoint = "0."   new string('#', 339);

Efficiency and Usability

This approach is highly efficient because the formatting and string manipulation are handled by the optimized unmanaged CLR code. For enhanced usability, consider defining the format string as a constant:

public static class FormatStrings
{
    public const string DoubleFixedPoint = "0.###################################################################################################################################################################################################################################################################################################################################################";
}

Important Note: Not Truly Lossless

While this method effectively mimics the display rounding of the "r" format specifier, it's not a perfectly lossless conversion. If round-tripping (converting to a string and back to a double without data loss) is paramount, consider alternative approaches, such as those employing the "r" format, for a more accurate solution.