C# Converting a string containing a floating point to an integer

Question

What is the best way to take a string which can be empty or contain "1.2" for example, and convert it to an integer? int.TryParse fails, of course, and I don't want to use float.TryParse and then convert to int.

Thanks!

Answer 1

Maybe you can try to delete everything after floating point using string functions and then convert to int. But seriously I don't think it's better than converting to float and then to int.

Answer 2

var a = (int)Convert.ToDouble("1.2");    

Note if you're using comma as a number separator in your operating system, you have to use IFormatProvider:

var a = (int)Convert.ToDouble("1.2", CultureInfo.InvariantCulture.NumberFormat); 

Another way to accomplish this task:

var a = int.Parse("1.2".Split('.')[0]);

Remember about:

• If you want to handle empty and null strings, write a method and add string.IsNullOrEmpty condition.
• To get decimal separator, you can use NumberFormatInfo.NumberDecimalSeparator property.
• You should also keep eye on rounding to avoid traps.
• Select casting, Parse, TryParse or Convert class wisely. Read more at:
  • How to: Convert a string to an int (C# Programming Guide)
  • How to: Determine Whether a String Represents a Numeric Value (C# Programming Guide)

Answer 3

I don't know what's wrong with parsing to a float and converting to an int. I doubt that any other way would be more efficient but here's an attempt:

//allows empty strings and floating point values
int ParseInt(string s, bool alwaysRoundDown = false)
 {
    //converts null/empty strings to zero
    if (string.IsNullOrEmpty(s)) return 0;

    if (!s.Contains(".")) return int.Parse(s);

    string parts = s.Split(".");
    int i = int.Parse(parts[0]);
    if (alwaysRoundDown || parts.Length==1) return i;

    int digitAfterPoint = int.Parse(parts[1][0]);
    return (digitAfterPoint < 5) ? i : i+1;
 }

In order to globalize the code you would need to replace "." with System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator.

Answer 4

I think another way of doing it would be splitting the string into pieces taking the decimal (.) as the delimiter and then parsing for the integer. Of course, I am yet to ask you if the string might contain values like "37.56 miles in 32.65 seconds" type values.

Considering there will be only one value (string or number) in the string, I can think of something in the following line:

public int64 GetInt64(string input)
{
    if (string.IsNullOrEmpty(input)) return 0;
    // Split string on decimal (.)
    // ... This will separate all the digits.
    //
    string[] words = input.Split('.');
    return int.Parse(words[0]);
}

Answer 5

int a = (int)Math.Round(float.Parse("0.9"));

You need to round it first unless you want 0.9f being converted to 0 instead of 1.

Answer 6

You can use the Visual Basic runtime Library to accomplish this from c#.

You need to add a reference to the assembly Microsoft.VisualBasic.dll to your solution.

Then the following code will do your conversion:

using VB = Microsoft.VisualBasic.CompilerServices;

class Program
{
    static void Main(string[] args)
    {
        int i = VB.Conversions.ToInteger("1.2");
    }
}