Question

We are trying to read each word from a text file and replace it with another word.
For smaller text files, it works well. But for larger text files we keep getting the exception: “String cannot be of zero length.
Parameter name: oldValue “

void replace()
    {
        string s1 = " ", s2 = " ";
        StreamReader streamReader;
        streamReader = File.OpenText("C:\\sample.txt");
        StreamWriter streamWriter = File.CreateText("C:\\sample1.txt");
        //int x = st.Rows.Count;
        while ((line = streamReader.ReadLine()) != null)
        {
            char[] delimiterChars = { ' ', '\t' };
            String[] words = line.Split(delimiterChars);
            foreach (string str in words)
            {
                s1 = str;
                DataRow drow = st.Rows.Find(str);
                if (drow != null)
                {
                    index = st.Rows.IndexOf(drow);
                    s2 = Convert.ToString(st.Rows[index]["Binary"]);
                    s2 += "000";                                        
                   // Console.WriteLine(s1);
                   // Console.WriteLine(s2);
                    streamWriter.Write(s1.Replace(s1,s2)); // Exception occurs here
                }
                else
                    break;
            }
        }
        streamReader.Close();
        streamWriter.Close();
    }

we’re unable to find the reason.
Thanks in advance.

Answer 1

When you do your string.Split you may get empty entries if there are multiple spaces or tabs in sequence. These can’t be replaced as the strings are 0 length.

Use the overload that strips empty results using the StringSplitOptions argument:

var words = line.Split(delimiterChars, StringSplitOptions.RemoveEmptyEntries);