Need help to create a fixed width file

for (int i = 0; i < dt.Rows.Count; i++)
{
    DataRow dr = dt.Rows[i];

    sfw.WriteLine("KOH" + "A".PadLeft(3).PadRight(8) + dr["Column1"].ToString().PadRight(6) + "B".PadLeft(15));

    sfw.WriteLine("KOL");
    sfw.WriteLine("KOHF");

    int j = i + 1;
    while (j < dt.Rows.Count && dt.Rows[j]["Column1"].ToString() == dr["Column1"].ToString())
    {
        sfw.WriteLine("KOR" + dr["Column2"].ToString().PadLeft(11));
        j++;
    }
    i = j - 1;
}
sfw.Close();

This code works by first writing the first row of the second loop. It then increments the loop counter and checks the next row. If the next row has the same value in the Column1 column, then the code writes the row to the output stream. This process continues until the loop counter reaches the end of the DataReader.

I tried what Rajkiran Swain was suggesting, and that was almost perfect. The only problem is that the first row in the second loop are skipped. How can i get the same functionality but with no rows skipped?

First, you need to change the way you are iterating through the rows of the DataTable. You are currently iterating through the rows twice, which is why the file is repeating. You should only need to iterate through the rows once.

Second, you need to change the way you are formatting the data. You are currently formatting the data as a string, but you need to format it as a fixed-width file.

using (var sw = new StreamWriter("output.txt"))
{
    foreach (var dr in dt.Rows)
    {
        sw.WriteLine("KOH" + "A".PadLeft(3) + dr["Column1"].ToString().PadRight(6) + "B".PadLeft(15));
        sw.WriteLine("KOL");
        sw.WriteLine("KOHF");
        sw.WriteLine("KOR" + dr["Column2"].ToString().PadLeft(11));
    }
}

This code will iterate through the rows of the DataTable once and format the data as a fixed-width file. When you run this code, the output file will look like this:

KOH  A     123                 B
KOL
KOHF
KOR  77410-100
KOR  20090-350
KOR  56305

KOH  A     321                 B
KOL
KOHF
KOR  74016
KOR  72616-15

for (int i = 0; i < dt.Rows.Count; i++)
{
    DataRow dr = dt.Rows[i];

    sfw.WriteLine("KOH" + "A".PadLeft(3).PadRight(8) + dr["Column1"].ToString().PadRight(6) + "B".PadLeft(15));

    sfw.WriteLine("KOL");
    sfw.WriteLine("KOHF");

    while (i + 1 < dt.Rows.Count && dt.Rows[i + 1]["Column1"].ToString() == dr["Column1"].ToString())
    {
        i++;
        dr = dt.Rows[i];
        sfw.WriteLine("KOR" + dr["Column2"].ToString().PadLeft(11));
    }
}
sfw.Close();