C#

    /// <summary>
    /// Result object for 'Ping' web method.
    /// </summary>
    [SoapInclude(typeof(PingResult))]
    [Serializable()]
    public class WebMethodResult
    {
        private Int32 a;
        private String[] b;
        private UInt32[] c;
        private UInt32[] d;
        private UInt32[] e;
        private Int16[] f;

        public Int32 A
        {
            get { return this.a; }
            set { this.a= value; }
        }
        [XmlArray()]
        public String[] B
        {
            get { return this.b; }
            set { this.b= value; }
        }
        [XmlArray()]
        public UInt32[] C
        {
            get { return this.c; }
            set { this.c= value; }
        }
        [XmlArray()]
        public UInt32[] D
        {
            get { return this.d; }
            set { this.d= value; }
        }
        [XmlArray()]
        public UInt32[] E
        {
            get { return this.e; }
            set { this.e= value; }
        }
        [XmlArray()]
        public Int16[] F
        {
            get { return this.f; }
            set { this.f= value; }
        }

        public WebMethodResult() 
        {
            //leave empty - serializer constructor
        }
}

<pingresult>
<returncode>1204</returncode>
-
<meternumber>
<string>12081056</string>
<string>12092171</string>
<string>12113456</string>
</meternumber>
-
<amiserialnumber>
<unsignedint>9245344</unsignedint>
<unsignedint>9317678</unsignedint>
<unsignedint>11110689</unsignedint>
</amiserialnumber>
-
<serviceaddresskey>
<unsignedint>500006497</unsignedint>
<unsignedint>500148477</unsignedint>
<unsignedint>500154274</unsignedint>
</serviceaddresskey>
-
<usagepointkey>
<unsignedint>500013896</unsignedint>
<unsignedint>500215109</unsignedint>
<unsignedint>500223149</unsignedint>
</usagepointkey>
-
<meterstatuscode>
<short>1122</short>
<short>1122</short>
<short>1122</short>
</meterstatuscode>
</pingresult>

...
//read filePath


foreach(string inFile in Directory.GetFiles(filePath))
{
  ...
  StreamReader sr = File.OpenText(inFile);            
  line = sr.ReadLine();            
  Console.WriteLine();            
  Console.WriteLine("Successful file open!...");            
  Console.WriteLine();
  Console.WriteLine("Input file name to save!");            
  Console.WriteLine("sample: d:\\filename.txt");            
  filePath = Console.ReadLine();
  FileStream file = new FileStream(filePath, FileMode.Create);              
  StreamWriter sw = new StreamWriter(file);    
  List lines = new List();            

  while ((line = sr.ReadLine()) != null)            
  {                
    lines.Add(line);            
  } 
  try           
  {                
    int numberOne = Int32.Parse(lines[0]);  
    int numberTwo = Int32.Parse(lines[1]);                
    int numberThree = Int32.Parse(lines[2]);                
    int x = numberOne + numberTwo + numberThree;                
    sw.WriteLine(x);            
  }            
  catch { }
  sw.Close();
  sr.Close();
}

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;

class MainClass
{
    public static void Main(string[] args)
    {
        string inFile, filePath;
        string line;
        //Console.WriteLine("Input file name to open!");
        //Console.WriteLine("Sample: d:\\filename.txt");
        //inFile = Convert.ToString(Console.ReadLine());
        foreach (string inFile in Directory.GetFiles(filePath))
        {
            StreamReader sr = File.OpenText(inFile);
            line = sr.ReadLine();
            Console.WriteLine();
            Console.WriteLine("Successful file open!...");
            Console.WriteLine();
            Console.WriteLine("Input file name to save!");
            Console.WriteLine("sample: d:\\filename.txt");
            filePath = Console.ReadLine();
            FileStream file = new FileStream(filePath, FileMode.Create);
            StreamWriter sw = new StreamWriter(file);
            List<string> lines = new List<string>();

            while ((line = sr.ReadLine()) != null)
            {
                lines.Add(line);
            }
            try
            {
                int numberOne = Int32.Parse(lines[0]);
                int numberTwo = Int32.Parse(lines[1]);
                int numberThree = Int32.Parse(lines[2]);
                int x = numberOne + numberTwo + numberThree;
                sw.WriteLine(x);
            }
            catch { }
            sw.Close();
            sr.Close();
        }

    }
}
        </string></string>

<br />
Error:<br />
A local variable named 'inFile' cannot be declared in this scope because it would give a different meaning to 'inFile', which is already used in a 'parent or current' scope to denote something else	<br />

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;

class MainClass
{
    public static void Main(string[] args)
    {
        string inFile;
        string line;

        const string inDir = "D:\\data\\A\\";
        const string outDir = "D:\\data\\B\\";
        DirectoryInfo di = new DirectoryInfo(inDir);
        FileInfo[] files = di.GetFiles("*.txt");
        foreach (FileInfo fi in files)
        {
            inFile = fi.FullName;
            StreamReader sr = File.OpenText(inFile);
            List<string> lines = new List<string>();

            while ((line = sr.ReadLine()) != null)
            {
                lines.Add(line);
            }
            
                int numberOne = Int32.Parse(lines[0]);
                //int numberTwo = Int32.Parse(lines[1]);
                int numberThree = Int32.Parse(lines[2]);
                //int x = numberOne + numberTwo + numberThree;
                int x = numberOne + numberThree;

            sr.Close();
            string destFile = Path.Combine(outDir, fi.Name);
            File.WriteAllText(destFile, Convert.ToString(x));
        }

    }
}
</string></string>