Formatting Fixed-width Text Output

[jmcilhinney]

C# version here.

Lots of people ask how to display text formatted in columns. It's generally a bad idea to display a solid block of text formatted that way. More often you should use a grid control or a ListView, but if you really want to display tabular data in a TextBox, or perhaps in a file with fixed-width columns, then you'd do it much like this:

Dim builder As New System.Text.StringBuilder
Dim format As String = "{0,-4}{1,-10}{2,-12:d}{3,8}"
 
builder.AppendFormat(format, "ID", "Name", "DOB", "Children")
builder.AppendLine()
builder.AppendFormat(format, 1, "Peter", #6/19/1969#, 2)
builder.AppendLine()
builder.AppendFormat(format, 2, "Paul", #4/23/1974#, 4)
builder.AppendLine()
builder.AppendFormat(format, 3, "Mary", #12/4/1980#, 1)
builder.AppendLine()
 
Me.TextBox1.Text = builder.ToString()

The secret there is the format string. You can use a format string with a StringBuilder.AppendFormat, Console.WriteLine, String.Format, StreamWriter.WriteLine and other places, so your output options are many. Let's take a closer look at that format string.

It includes 4 format specifiers, so it will accept 4 values to format. You'll see that each call to AppendFormat passes the format string followed by 4 values. Funny, that.

The first format specifier ({0,-4}) takes the first value ({0,-4}) and pads it out with whitespace to 4 characters ({0,-4}), left-aligning the string ({0,-4}).

The second format specifier take the second value, pads it out to 10 characters and left-aligns it.

The third format specifier ({2,-12:d}) takes the third value, pads it out to 12 characters, left-aligns it and displays it in the short date format ({2,-12:d}).

The fourth format specifier takes fourth value and pads it out to 8 characters, but this time the field width is greater than zero so it is right-aligned.

Note that to actually view the output in columns you must use a fixed-width font. Notepad will do that by default but if, if you're displaying the data in a TextBox, you must set the Font to Courier New or some other appropriate value.