Issue with too expensive search txt store to datatable - hanging WinForm GUI - Foreach+Switch vs. something?

Question 1

As stated in question, this answer only applies to MS Access Database, if you use Oracle or SQL Server just launch a Bulk load

Well, after a lot of contributions (see comments above specially from Voo) and a lot of stackoverflow research, I could improve the performance from 7 days to 45 minutes processing total 16 million lines, line-by-line.

The key after well-oriented tips from people in comments, was to use DAO (with some worries about deployment the database with ClickOnce - notice the dbName connection string).

A lot of usefull information can be found here: StackOverflow-Writing-large-records

If you use accdb, you need to do a modification in using ADO to: using DAO = Microsoft.Office.Interop.Access.Dao;
(can be found in Visual Studio add reference in COM Type references, you need to add the Microsoft Office xx.x Access Database Engine Object Library - but remember that this imposes a great limitation to your end-user specs.

I noticed some improvements needed to store all iterations in DAO (BARR, TRECH, so on..) but its code-optimization, not the main issue in this post.

Dont know the reason why .NET doenst add a bulk insert for MS Access.

The code above for each file, takes 0.3 seconds to pass switch statments, and 1.33 minutes to DAO-saving. If doing for all 80 files takes 45 minutes

 private void Button_extract_element_Click(object sender, EventArgs e)
 {
 TestObject test = new TestObject();
 test._shouldstop = true;
 backgroundWorker1.RunWorkerAsync(test);
 int passes = 0;

 Label_extract_element.Text = "wait processing....";
 Label_extract_element.Refresh();
 Label_extract_element.Update();

 //this should keep winform waiting for thread-return, showing passes
 while (test._shouldstop)
 {
    passes++;
    Label_extract_element.Text = "wait processing...." + passes;
    Label_extract_element.Refresh();
    Label_extract_element.Update();
 }
 Label_extract_element.Text = " OK, done!";
 Label_extract_element.Refresh();
 Label_extract_element.Update();
 } //End of Button_extract_element_Click

 class TestObject
 {
 public bool _shouldstop { get; set; }
 }   

 //backgroundWorker complete actions 
 private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
 {
    // Receive the result from DoWork, and display it.
    TestObject test = e.Result as TestObject;
 }

 private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
 {
 TestObject argumentTest = e.Argument as TestObject;
 argumentTest._shouldstop = true;
 string loop = "";
 string[] ListOfFilesinDir = Directory.GetFiles(GlobalVariables.folder, "*.txt").Select(Path.GetFileName).ToArray();

 foreach (string filename in ListOfFilesinDir)
 {
    int count_barr = 0;
    int count_lines = 0;
    //ReadAll seems to process really fast - not a gap
    string[] FLines = File.ReadAllLines(GlobalVariables.folder + "\\" + filename);

    int[] line_barr = new int[FLines.Count()];

    foreach (string Lines in FLines)
    {
    count_lines++;
    switch (Lines)
    {
       case "SE;":
       GlobalVariables.SEstr = FLines[count_lines].Split(';')[3].Trim();
       break;

       case "CKT;":
       GlobalVariables.codCktAL = FLines[count_lines].Split(';')[2].Trim();
       GlobalVariables.nomeCktAL = FLines[count_lines].Split(';')[10].Trim();
       GlobalVariables.nomeArqv = filename;
       break;

       case "BARR;": loop = "BARR;"; break;
       case "TRECH;": loop = "TRECH;"; break;
       case "CAP;": loop = "CAP;"; break;
       case "INST;": loop = "INST;"; break;
       case "KEY;": loop = "KEY;"; break;
       case "REG;": loop = "REG;"; break;
       case "DMD;": 
          loop = "DMD;"; 
          GlobalVariables.TRAFO = (FLines[count_lines-8].Split(';')[1].Trim());
          break;
    }

    switch (loop)
    {
       // I'll post just the first case, so I dont go soooo long in this post..
       //This part seems to process really fast

       case "BARR;":
          GlobalVariables.parse_results = "";

          //take next line and test if is one of the nexts TAGs, and break loop:
          GlobalVariables.parse_results += FLines[count_lines];

          if (Equals(GlobalVariables.parse_results, "TRECH;") || Equals(GlobalVariables.parse_results, "CAP;") || Equals(GlobalVariables.parse_results, "INST;") || Equals(GlobalVariables.parse_results, "KEY;") || Equals(GlobalVariables.parse_results, "REG;") || Equals(GlobalVariables.parse_results.Split(';')[0], "ET") || Equals(GlobalVariables.parse_results.Split(';')[0], "EP"))
          {
             GlobalVariables.parse_results = "";
             loop = "";
             break;
          }
          else  
          {
             //store the number of the line to array for later reference
             count_barr++;
             line_barr[count_barr] = count_lines;
             break;
          }
          case "TRECH;": /*repeat all in BARR loop for TRECH's 20 fields*/ break;
          case "CAP;": /*same repeat for different n fields*/ break;
          case "INST;": /*same repeat for different n fields*/ break;
          case "KEY;": /*same repeat for different n fields*/ break;
          case "REG;": /*same repeat for different n fields*/ break;
    } //end of switch
 } //end for each lines

string dbName = Application.StartupPath + "\\Resources";
DAO.DBEngine dbEngine = new DAO.DBEngine();
DAO.Database db = dbEngine.OpenDatabase(dbName+"\\DataBase.accdb");

// From here, could work more to store different Tables with different fields, dynamically, improving code

DAO.Recordset rs = db.OpenRecordset("BARRA_MT");   

for (int i = 1; i < (count_barr+1); i++)
{
   rs.AddNew();
   double b0 = Convert.ToDouble(FLines[line_barr[i]].Split(';')[0].Trim());
   string b1 = FLines[line_barr[i]].Split(';')[1].Trim().ToString();
   double b2 = Convert.ToDouble(FLines[line_barr[i]].Split(';')[2].Trim());
   double b3 = Convert.ToDouble(FLines[line_barr[i]].Split(';')[3].Trim());
   rs.Fields["BARR_MT"].Value = b0;
   rs.Fields["COD"].Value = b1;
   rs.Fields["X"].Value = b2;
   rs.Fields["Y"].Value = b3;
   rs.Update();
}
rs.Close();     
db.Close();

argumentTest._shouldstop = false;
e.Result = argumentTest;
} //end`

Question 2

Your answer still is problematic. Use the following example to not read all lines into memory:

System.IO.StreamReader file = 
   new System.IO.StreamReader("c:\\test.txt");
while((line = file.ReadLine()) != null)
{
   Console.WriteLine (line);
   counter++;
}

There is no need for a tiny file like yours to take that long. I process files with about half a billion events (granted, those are binary coded, but waaaaaaay more than your 200.000 lines) in minutes. You're wasting lots of time by doing things like allocating an array of lines instead of reading the files line by line.