What is the difference between String and string in C#?

In C#, both String and string are used to represent text-based data, but they are not exactly the same. string is an alias for the System.String class. They can be used interchangeably, and the choice between using string or String is mostly a matter of coding style.

Here's an example demonstrating the usage of both string and String:

csharp

using System;

class Program
{
    public static void Main()
    {
        string str1 = "Hello, using string"; // Using the alias 'string'
        String str2 = "Hello, using String"; // Using the class name 'String'

        Console.WriteLine(str1);
        Console.WriteLine(str2);

        // Compare using string.Equals (string is an alias)
        bool areEqual = string.Equals(str1, str2, StringComparison.OrdinalIgnoreCase);
        Console.WriteLine("Are equal? " + areEqual);
    }
}

In the example, str1 and str2 are two string variables that hold the same text but are declared using the alias string and the class name String, respectively. They can be used interchangeably.

The string.Equals method is used to compare the two strings. Since string is an alias for System.String, you can use either string.Equals or String.Equals to perform the comparison.

In practice, it's more common to use the string alias for string variables and methods due to C# coding conventions. However, both forms are valid and will produce the same results.