HexString到十进制转换错误：索引超出范围。 必须是非负数且小于集合的大小。 参数名称：startIndex

Question

I try to make a receiver software which convert hexadecimal value from serial to decimal value. This is my code :

       // Obtain the number of bytes waiting in the port's buffer 
       int bytes = comport.BytesToRead;

        // Create a byte array buffer to hold the incoming data
        byte[] buffer = new byte[bytes];

        // Read the data from the port and store it in our buffer
        comport.Read(buffer, 0, bytes);

        string hexValues = ByteArrayToHexString(buffer);
        string[] hexValuesSplit = hexValues.Split(' ');
        foreach (String hex in hexValuesSplit)
        {
            // Convert the number expressed in base-16 to an integer. 
            int value = Convert.ToInt32(hex, 16);
            Log(LogMsgType.Incoming, value+" ppm \n");
        }

But when I try to send data from serial it always say that "Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: startIndex". So What shoul I do?

Answer 1

Problem : while using String.Split() function if the string is EMPTY then it returns EMPTY string,

I suspect this statement causes the Exception:

int value = Convert.ToInt32(hex, 16);

if the hex value is Empty then it causes the Index was out of range. Must be non-negative Exception. Index was out of range. Must be non-negative Exception.

Solution 1: You need to Remove the empty entries by providing StringSplitOptions.RemoveEmptyEntries as second argument to the Split() function.

Try This:

string[] hexValuesSplit = hexValues.Split(new []{' '},StringSplitOptions.RemoveEmptyEntries);

OR

Solution 2 : You can simply check the hex variable for Null or Empty using String.IsNullOrEmpty() method.

string[] hexValuesSplit = hexValues.Split(' ');
foreach (String hex in hexValuesSplit)
{
 if(!String.IsNullOrEmpty(hex))
 {
   // Convert the number expressed in base-16 to an integer. 
   int value = Convert.ToInt32(hex, 16);
   Log(LogMsgType.Incoming, value+" ppm \n");
 }
}