String chars

Strings contain characters. These char values can be accessed with an indexer expression in the C# language. We can test and loop over chars.

Char notes

We can store these chars in separate variables. We cannot mutate (assign) chars in a string. But we can use them to build up new strings.

An example

We access a character by using the square brackets. To get the first character, you can specify variable[0]. To get the last character, you can subtract one from the length.

using System;

// Get values from this string.
string value = "hat";
char first = value[0];
char second = value[1];
char last = value[value.Length - 1];

// Write chars.
Console.WriteLine("FIRST: {0}", first);
Console.WriteLine("SECOND: {0}", second);
Console.WriteLine("LAST: {0}", last);
FIRST: h
SECOND: a
LAST: t

Example 2

When you have a string that is null, it does not point to any object data, and you cannot use the indexer on it. Therefore, the character accesses will not succeed.

using System;

// Array of string values.
string[] values = { "Dot Net Perls", "D", "", "Sam" };

// Loop over string values.
foreach (string value in values)
{
    // Display the string.
    Console.WriteLine("--- '{0}' ---", value);

    // We can't get chars from null or empty strings.
    if (!string.IsNullOrEmpty(value))
    {
        char first = value[0];
        char last = value[value.Length - 1];

        Console.Write("First char: ");
        Console.WriteLine(first);

        Console.Write("Last char: ");
        Console.WriteLine(last);
    }
}
--- 'Dot Net Perls' ---
First char: D
Last char: s
--- 'D' ---
First char: D
Last char: D
--- '' ---
--- 'Sam' ---
First char: S
Last char: m

Internals

An indexer is a property. It allows you to access the object's data using the square brackets, such as in variable[0].

.property instance char Chars
{
    .get instance char System.String::get_Chars(int32)
}

A discussion

Often we need to loop over the individual characters in a string. You can do this with the foreach loop, or with the for iterative statement using the char accessors.

A summary

Characters in strings can be accessed, but not modified. We saw some issues relating to empty and null strings and trying to access their characters.