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.

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.

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)
}

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.

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.