Truncate decimals instead of Rounding from a double value In C#

Introduction

Many times while working on applications, we often land into a situation where we want to truncate the decimal places from a number instead of round like suppose we have 5.329 and I want to truncate the third digit then my required output will be 5.32. Here, I will walk through the different ways which I know in which we can achieve the same.

Approaches

I have created the approaches as making the C# method.

1.      Truncate the decimals through the string operations.

Below method only usable if you want to truncate the decimal places to two.

#region Round

/// <summary>

/// Truncate the last digit after two digit floating points.

/// </summary>

/// <param name="value">A double-precision floating-point number to be rounded.</param>

/// <returns>Double value contains two digit floating points.</returns>

public static double Round (double value)

{

  double returnValue = 0;

  try

  {

    //Convert the value into the string for round.

    string input = Convert.ToString(value);

    //Check if the input contains decimal places

    if (input.Contains("."))

    {

      //Check if there are 3 or more digits after the decimal point.

      if (input.Length - input.IndexOf(".", StringComparison.Ordinal) >= 4)

      {

        //Replace the input value with the required value.

        //Added 3 to get only 2 digits after the decimal point.

        input = input.Substring(0, input.IndexOf(".", StringComparison.Ordinal) + 3);

      }

    }

        //Converts the string representation of a number to its System.Double equivalent.

    returnValue = Convert.ToDouble(input);

  }

  catch { } //Suppress exception no need to handle.

  return returnValue;

}

#endregion

2.      Truncate the decimals through the mathematical operations.

Through this method you can truncate any number of decimal places.

#region Round

/// <summary>

/// Rounds a decimal value to a specified number of fractional digits.

/// </summary>

/// <param name="value">A decimal number to be rounded.</param>

/// <param name="decimals">The number of decimal places in the return value.</param>

/// <returns>The number nearest to value that contains a number of fractional digits equal to decimals.</returns>

public static double Round(double value, byte decimals)

{

  double returnValue = 0;

  try

  {

    if (value != 0)

    {

      //Gets the power of 10 base on passed decimal parameter value (10^decimals).

      double powValue = Math.Pow(10, decimals);

      //Gets the truncated value.

      returnValue = Math.Truncate(CDCommon.ToDouble(value * powValue)) / powValue;

    }

  }

  catch

  { throw; }

  return returnValue;

}

#endregion

Conclusion

From both the ways, as per my opinion prefer the second approach in implementation because it’s very light compared to the first in terms of calculations.