How Can I Control Which Line I Add Items Of An Array To

Question

1.18/5 (3 votes)

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I need to print a file to a listbox in groups of 5. Its a combination of 3 letters and i need the listbox to read;
"Line 001: ABC DEF GHI JKL MNO
Line 002: PQR STU VWX YZA"

except replacing the letters with the combinations in the file obviously and since the file can be switched the number of lines is not definite and needs to count up continuously but always hold 3 digits. Please help. Thanks

So far i have something like this but idk if its correct

C#

public partial class frmDNA : Form
   {
       int x = 1;
       String Path;
       StreamReader DNAFile = new StreamReader("/documents/visual studio 2013/Projects/DNA/DNA.txt");
       int Index;
       int Lines = File.ReadLines("/documents/visual studio 2013/Projects/DNA/DNA.txt").Count();
       public frmDNA()
       {
           InitializeComponent();
       }
      private void btnPrint_Click(object sender, EventArgs e)
       {
           String DNA = "Line " + x.ToString("000") + " = ";
           string[] DNAarray = new string[Lines];
           int Begin, end;
           Begin = 0;
           end = 5;
           while (Index < DNAarray.Length && !DNAFile.EndOfStream)
           {
               DNAarray[Index] = DNAFile.ReadLine();
               while (Begin < end)
               {
                   DNA  += DNAFile.ReadLine() + " ";
                   Begin++;
                   x++;
               }
               end += 5;
               Index++;
               lstOut.Items.Add(DNA);
               Begin += 5;
           }



       }

       private void frmDNA_Load(object sender, EventArgs e)
       {

       }
   }

But

C#

lstOut.Items.Add(DNA);

is showing up as wrong saying DNA is unassigned.

Posted 29-Apr-15 17:47pm

Member 11561872

Updated 30-Apr-15 12:21pm

v5

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Comments

gggustafson 30-Apr-15 0:03am

Do you mean "read a file to a ListBox"?

Member 11561872 30-Apr-15 0:03am

aren't they the same thing?

gggustafson 30-Apr-15 0:19am

I don't know what "print a file to a ListBox" means. Files are read or written. ListBoxes have items added or deleted. If you are trying to read the contents of a file into a ListBox, then please say so. And supply some code that you have tried (supply code by using the Improve Question button.

Member 11561872 30-Apr-15 0:31am

Then I mean read. I need to take lines of a text file and output them to a listbox. I can't do actual code atm as I'm away from the computer but I have the file opened and the data put into a simple string array. But I don't know how to make it so each line reads specific text then has a specific number of groups after.

gggustafson 30-Apr-15 9:19am

See my solution below

StM0n 30-Apr-15 0:26am

What kind of file is it: A text or some binary file?

Member 11561872 30-Apr-15 0:31am

Text

Sergey Alexandrovich Kryukov 30-Apr-15 1:15am

What have you tried so far?
—SA

Member 11561872 30-Apr-15 16:16pm

i updated the question to show it

Sergey Alexandrovich Kryukov 30-Apr-15 16:27pm

All right, thank you for the update. Yes, DNA can be unassigned (and uninitialized) if the inner loop is never executed, so please check it up under the debugger.
—SA

Member 11561872 30-Apr-15 17:31pm

ok so I figured out how to get rid of the error. I simply added the line "DNA = "";". But now it won't show the results. It merely adds "Line 001 =" to the list box. Would it reset DNA back to "" after the loop completes?

Sergey Alexandrovich Kryukov 30-Apr-15 17:50pm

Don't use "", use string.Empty or null, depending on what you want. Then you would be adding empty string to items, which might be not what you need.
—SA

Member 11561872 30-Apr-15 17:59pm

So i read somewhere else on here you can append to string by using sting += appendage so i tried that. The code is updated now but it just returns "Line 000 = System.String[] System.String[]..." indefinitely

Sergey Alexandrovich Kryukov 30-Apr-15 18:23pm

Your code is quite weird. What do you want to achieve with that? Anyway, use the debugger.
—SA

Member 11561872 30-Apr-15 18:23pm

Ok so fixed that. I updated the question again but it now outputs the same 5 lines every time. Now it only reads: "Line 000 = ABC DEF GHI JKL MNO" for every line

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gggustafson · Answer 1 · 2015-04-30T03:22:00

First, Google "c# read line of text file". Refer to the MSDN example.

I prefer to use a using statement rather than opening and closing a file. Replace the body of the example's while statement with whatever editing you need to perform on line and then add line to the ListBox.

The following example assumes that System.IO and System.Text appear in a using directive. Replace c:\\gustafson\\test.txt with the name of your text file

C#

public void read_file_into_listbox ( )
    {
    StringBuilder   concatenated = new StringBuilder ( );
    int             item_count = 0;
    string          line;
    int             line_count = 0;

    list_box.BeginUpdate ( );
    using ( StreamReader file =
                         new StreamReader (
                            "c:\\gustafson\\test.txt" ) )
        {
        concatenated.Append ( "Line " );
        while ( ( line = file.ReadLine ( ) ) != null )
            {
            item_count++;
            if ( item_count == 1 )
                {
                line_count++;
                concatenated.AppendFormat (
                    "{0:d3}: {1} ",
                    line_count,
                    line.ToUpper ( ).Trim ( ) );
                }
            else if ( item_count == 5 )
                {
                concatenated.AppendFormat (
                    "{0}",
                    line.ToUpper ( ).Trim ( ) );
                list_box.Items.Add (
                    concatenated.ToString ( ) );
                concatenated.Length = 0;
                concatenated.Append ( "Line " );
                item_count = 0;
                }
            else
                {
                concatenated.AppendFormat (
                    "{0} ",
                    line.ToUpper ( ).Trim ( ) );
                }
            }
        if ( item_count > 0 )
            {
            list_box.Items.Add ( concatenated.ToString ( ) );
            }
        }
    list_box.EndUpdate ( );
    }
}

Although string concatenation can occur by using the + operator, more efficient string manipulation can be had by using StringBuilder.

When this code executes, the edited lines of the file will appear in the listbox.

Hope that helps.