Question

I’m trying to convert one value to another. I am importing a text file, using streamreader/writer. I want to know if I can have the part of the while loop inside the if statement wait until the the rest of the loop finishes before writing what its supposed to. I know this is probably an easy question but for some reason I can put my finger on it. I am not using multithread processing and want to stay away from asynch.

using (StreamReader reader = new StreamReader(convertInput))
{
    string line;
    writer.WriteLine(formatter, "Original Value", "Converted Value");
    writer.WriteLine(formatter, "--------------", "---------------");
A:  while ((line = reader.ReadLine()) != null)
    {
            string str2BeConverted = line;
            long numHexToDex;
            if ((Int64.TryParse(line, NumberStyles.HexNumber, null, out numHexToDec)) == false)
            {
                    writer.WriteLine();
                    writer.Write(line + " " + "is not a Hexadecimal value.");
                    goto A;
            }

            Int64.TryParse(line, NumberStyles.HexNumber, null, out numHexToDec);
            string lineChanged = numHexToDec.ToString("G");
    }
}

I am wanting to wait until all the values that parse successfully are written, then write the ones that didn’t at the end.

Answer 1

The easiest way is to write these to some sort of buffer instead, such as a StringBuilder, and then write the StringBuilder’s contents out after all the successful elements were processed:

using (StreamReader reader = new StreamReader(convertInput))
{
    string line;
    Stringbuilder builder = new StringBuilder();
    writer.WriteLine(formatter, "Original Value", "Converted Value");
    writer.WriteLine(formatter, "--------------", "---------------");
    while ((line = reader.ReadLine()) != null)
    {
            string str2BeConverted = line;
            long numHexToDex;
            if ((Int64.TryParse(line, NumberStyles.HexNumber, null, out numHexToDec)) == false)
            {

                    builder.AppendLine();
                    builder.Append(line + " " + "is not a Hexadecimal value.");
                    continue; //there is ALWAYS an alternative to goto
            }

            Int64.TryParse(line, NumberStyles.HexNumber, null, out numHexToDec);
            string lineChanged = numHexToDec.ToString("G");
    }

    writer.Write(builder.ToString();
}

Also, as many comments have stated, code that uses goto is NEVER good code. There is ALWAYS something else you could do that is more correct, and in this case it’s extremely simple (the continue keyword will bypass the rest of the loop block, re-evaluate the while condition, and iterate further if indicated).