String.Substring Method (Int32, Int32) throws ArgumentOutOfRangeException

Question

I have a string where the first 5 characters are never empty and from char 6 to the end data is variable leght. Something like this:

string inData = comPort1.ReadExisting();
//Console.WriteLine("inData: " + inData);
string origMsg = inData.Substring(4, 1);
//Console.WriteLine("origMsg: " + origMsg);
string seAnex = inData.Substring(5, 15);           // ArgumentOutOfRangeException
inData = inData.Substring(5, inData.Length - 8);
//Console.WriteLine("new inData: " + inData);

if (seAnex == "some_text_15_ch")
{
    //...
}
else
{
    //...
}

Output:

inData: {1112Test}
origMsg: 2
new inData: Test

This code throws a ArgumentOutOfRangeException: Index and length must refer to a location within the string . How can I solve this?

Answer 1

string origMsg = inData.Substring(4, 1);

"startIndex cannot be larger than length of string"

in other words,

4 cannot be larger than length of inData

4 is larger than length of inData

inData.Length is less than 4

Answer 2

I'm not sure what do you want to do with your code. But, if just to resolve the exception. You can fix like this:

        string inData = comPort1.ReadExisting();
        //Console.WriteLine("inData: " + inData);
        if (inData.Length >= 5)
        {
            string origMsg = inData.Substring(4, 1);
            //Console.WriteLine("origMsg: " + origMsg);
            //string seAnex = inData.Substring(5, 15);           // ArgumentOutOfRangeException
            string seAnex = inData.Substring(5, inData.Length - 5);
            //inData = inData.Substring(5, inData.Length - 8);
            //Console.WriteLine("new inData: " + inData);

            if (seAnex == "some_text_15_ch")
            {
                //...
            }
            else
            {
                //...
            }
        }

I guess your purpose can be get data information from a message have format like "{111abcxzy}" in a long data string "{111abcxzy}{111abcxzy}{..." that received from COM communication ?

Answer 3

I would bet that you do not have the string value you say that you do. If it were in fact 5+ characters long, you would not have and ArgumentOutOfRange exception when you call SubString(4,1) on it. Print out the value or inspect it in the debugger to confirm