Creating a fixed width file in C#

Question

What is the best way to create a fixed width file in C#. I have a bunch of fields with lengths to write out. Say 20,80.10,2 etc all left aligned. Is there an easy way to do

Answer 1

Darren's answer to this question has inspired me to use extension methods, but instead of extending String, I extended StringBuilder. I wrote two methods:

public static StringBuilder AppendFixed(this StringBuilder sb, int length, string value)
{
    if (String.IsNullOrWhiteSpace(value))
        return sb.Append(String.Empty.PadLeft(length));

    if (value.Length <= length)
        return sb.Append(value.PadLeft(length));
    else
        return sb.Append(value.Substring(0, length));
}

public static StringBuilder AppendFixed(this StringBuilder sb, int length, string value, out string rest)
{
    rest = String.Empty;

    if (String.IsNullOrWhiteSpace(value))
        return sb.AppendFixed(length, value);

    if (value.Length > length)
        rest = value.Substring(length);

    return sb.AppendFixed(length, value);
}

First one silently ignores too long string and simply cuts off the end of it, and the second one returns cut off part through out parameter of the method.

Example:

string rest;    

StringBuilder clientRecord = new StringBuilder();
clientRecord.AppendFixed(40, doc.ClientName, out rest); 
clientRecord.AppendFixed(40, rest);
clientRecord.AppendFixed(40, doc.ClientAddress, out rest);
clientRecord.AppendFixed(40, rest);

Answer 2

You can use string.Format to easily pad a value with spaces e.g.

string a = String.Format("|{0,5}|{1,5}|{2,5}", 1, 20, 300);
string b = String.Format("|{0,-5}|{1,-5}|{2,-5}", 1, 20, 300);

// 'a' will be equal to "|    1|   20|  300|"
// 'b' will be equal to "|1    |20   |300  |"