Convert string to double: input string was not in a correct format

Question

I am getting some values from my Arduino over the serial port. The data has the format: "value1,value2,value3\r" as a string.

Example: "4.5,550.0,0.02\r"

I can recieve and separate the values but when I try to convert them to double I get the following exception

"input string was not in a correct format"`.

double Battery = 0, Voltage = 0, Current = 0;

private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    string data = serialPort1.ReadLine();
    string bv = data.Substring(0, data.IndexOf(",") - 1);
    data = data.Substring(data.IndexOf(",") + 1);
    string v0 = data.Substring(0, data.IndexOf(",") - 1);
    data = data.Substring(data.IndexOf(",") + 1);
    string i = data;

    double batteryVoltage = Convert.ToDouble(bv);
    double V0 = Convert.ToDouble(v0);
    double I = Convert.ToDouble(i);

    Battery = batteryVoltage;
    Voltage = V0;
    Current = I;

}

You've abused Substring quite a lot here, what is wrong with string.Split(',') and TryParse? — Sayse
– Sayse, Commented Sep 18, 2013 at 9:46
This code works with your sample data. Please, give data which causes error — Sergey Berezovskiy
– Sergey Berezovskiy, Commented Sep 18, 2013 at 9:48
Are you sure your input is 4.5,550.0,0.02\r and not 4.5,550.0,0.02\\r? — sloth
– sloth, Commented Sep 18, 2013 at 9:52
@user2790895 can you give us value of data when you get exception? — Sergey Berezovskiy
– Sergey Berezovskiy, Commented Sep 18, 2013 at 9:56
Since some people aren't aware of this - the sample data fails on certain regional settings, e.g. Polish uses "," as a decimal point and doesn't consider "4.5" a proper string to convert. — S_F
– S_F, Commented Sep 18, 2013 at 10:35

S_F · Accepted Answer · 2013-09-18 09:53:37Z

13

Two things are a problem here. First, the conversion may fail because of regional settings (invalid decimal point character), so use CultureInfo.InvariantCulture from System.Globalization namespace as an additional parameter. Second thing, you are cutting off one character from your substrings, so remove -1.

string data = "4.5,550.0,0.02\r";
string bv = data.Substring(0, data.IndexOf(","));
data = data.Substring(data.IndexOf(",") + 1);
string v0 = data.Substring(0, data.IndexOf(","));
data = data.Substring(data.IndexOf(",") + 1);
string i = data;

double batteryVoltage = Convert.ToDouble(bv, CultureInfo.InvariantCulture);
double V0 = Convert.ToDouble(v0, CultureInfo.InvariantCulture);
double I = Convert.ToDouble(i, CultureInfo.InvariantCulture);

answered Sep 18, 2013 at 9:53

S_F

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2 Comments

Sergey Berezovskiy Over a year ago

Good notice on cutting off last character. That probably will be the reason of error

S_F Over a year ago

Right, fixed my answer as it does mess with the conversion. Still, CultureInfo setting should be there if the user has a regional setting which doesn't recognize "." as a decimal point.

Caroline Aime · Accepted Answer · 2013-09-18 09:49:12Z

0

Possible the \r char is causing the issue. Try trimming it before processing.

answered Sep 18, 2013 at 9:49

Caroline Aime

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Comments

Rik · Accepted Answer · 2013-09-18 10:10:45Z

0

Your code works for me with the provided example input. Can you elaborate on the exception?

Try specifying the CultureInfo in the conversion.

Also, you should use the String.Split() method:

string data = "4.5,550.0,0.02\r";
var strings = data.Split(',');
var doubles = strings.Select(s => Convert.ToDouble(s, CultureInfo.InvariantCulture)).ToList();

double batteryVoltage = doubles[0];
double V0 = doubles[1];
double I = doubles[2];

edited Sep 18, 2013 at 10:10

answered Sep 18, 2013 at 9:48

Rik

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2 Comments

Sergey Berezovskiy Over a year ago

It should be a comment to question, not an answer to the reason of error

Sayse Over a year ago

and it will also probably fail on 0.02\r

Suraj Singh · Accepted Answer · 2013-09-18 10:54:00Z

0

Try this to split your string

 string[] separotrs = { ",", "\r" };
 string[] result= aurdino.Split(separotrs, StringSplitOptions.RemoveEmptyEntries);

       double batteryVoltage = Convert.ToDouble(result[1]); //Sorry if order is incorrect:-)
       double v0 = Convert.ToDouble(result[0]);
       double I = Convert.ToDouble(result[2]);

One thing i do not get is where exactly are you getting error however your method will not fetch correct numbers(cutting off the last value) ,and you variable i (Current) will fetch 0.02\r which will be handled by Convert.ToDouble and you will get 0.02 as your Current value however other values will be wrong but i don't think you are getting error on this method as per your example.

See here

edited Sep 18, 2013 at 10:54

answered Sep 18, 2013 at 10:21

Suraj Singh

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