PadRight, PadLeft

PadRight adds spaces to the right of strings. PadLeft meanwhile adds to the left. These C# methods make text easier to read.

Padding a string adds whitespace or other characters to the beginning or end. Any character can be used for padding—not just spaces.

PadRight

This method can be used to create columns of text that are left-aligned. We add padding (on the right) up to the specified numbers of characters. This creates a column.

using System;

// Pad a string to 3 chars, and use Console methods to write it.
string value = "x".PadRight(3);
Console.Write(value);
Console.WriteLine("y");
x  y

Example 2

This next example is similar to the first one, but it uses a foreach-loop to build up a columnar layout. It shows how to call PadRight on string literals.

using System;

string[] a = new string[]
{
    "cat",
    "poodle",
    "lizard",
    "frog",
    "photon"
};

// Output the header.
Console.Write("Key".PadRight(15));
Console.WriteLine("Value");

// Output array.
foreach (string s in a)
{
    Console.Write(s.PadRight(15));
    Console.WriteLine("noun");
}
Key            Value
cat            noun
poodle         noun
lizard         noun
frog           noun
photon         noun

Example 3

In many applications, numeric values are aligned to the right. This is how Excel aligns numbers. We see that the numbers on the right are aligned to the right edge.

using System;

int[] a = new int[]
{
    1,
    40,
    6,
    700
};

// Output the header.
Console.Write("Letter".PadRight(10));
Console.WriteLine("Number".PadLeft(8));

// Output array.
foreach (int i in a)
{
    Console.Write("A".PadRight(10));
    Console.WriteLine(i.ToString().PadLeft(8));
}
Letter      Number
A                1
A               40
A                6
A              700

Chars

You can use special characters, such as a dot or dash, for padding. You could use PadRight and PadLeft with periods and connect a string with a right-aligned number.

using System;

Console.Write("Sam".PadRight(10, '.'));
Console.WriteLine("535".PadLeft(4, '.'));

Console.Write("Jason".PadRight(10, '.'));
Console.WriteLine("1".PadLeft(4, '.'));
Sam........535
Jason........1

PadLeft

Here the PadLeft method is tested with two parameters. The first is the column width in characters and the second is the padding character.

using System;

string[] words = { "1", "200", "Samuel", "Perls" };
foreach (string word in words) // Loop over words.
{
    // Write ten characters.
    Console.WriteLine(word.PadLeft(10, '_'));

    // Write ten characters with space.
    Console.WriteLine(word.PadLeft(10));
}
_________1
         1
_______200
       200
____Samuel
    Samuel
_____Perls
     Perls

Format string

We can avoid PadRight and PadLeft completely and instead use a format string. This can combine padding methods with other string operations.

using System;

string[] values = { "bird", "0", "1" };
foreach (string value in values)
{
    // Use an argument to formatting string for padding.
    // ... Positive means "pad right."
    // ... Negative (not shown) means "pad left."
    string padded = string.Format("{0,5}", value);
    Console.WriteLine(padded);
}
 bird
    0
    1

String literals

These are string objects, and we can pad them. String literals like "Word" can have PadRight called on them. Literals with padding can make headers for our text tables.

Optimization

We can improve performance with a cache of the padded strings—in a Dictionary or array. This is a form of precomputed lookup tables.

A summary

We used the PadRight and PadLeft methods. Padding methods are helpful when developing columnar layouts of numeric data, as with decimal places.