[Solved] How to convert a double value to string without rounded [duplicate]

You can use the Floor method to round down:

string str = (Math.Floor(dou * 10.0) / 10.0).ToString("0.0");

The format 0.0 means that it will show the decimal even if it is zero, e.g. 99.09 is formatted as 99.0 rather than 99.

Update:

If you want to do this dynamically depending on the number of digits in the input, then you first have to decide how to determine how many digits there actually are in the input.

Double precision floating point numbers are not stored in decimal form, they are stored in binary form. That means that some numbers that you think have just a few digits actually have a lot. A number that you see as 1.1 might actually have the value 1.099999999999999945634.

If you choose to use the number of digits that is shown when you format it into a string, then you would simply format it into a string and remove the last digit:

// format number into a string, make sure it uses period as decimal separator
string str = dou.ToString(CultureInfo.InvariantCulture);
// find the decimal separator
int index = str.IndexOf('.');
// check if there is a fractional part
if (index != -1) {
  // check if there is at least two fractional digits
  if (index < str.Length - 2) {
    // remove last digit
    str = str.Substring(0, str.Length - 1);
  } else {
    // remove decimal separator and the fractional digit
    str = str.Substring(0, index);
  }
}