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

Difference Between String and string in C#

In C#, String and string are two ways to refer to the same type, but they have different connotations and uses in the code. Here’s a detailed explanation of the differences and when to use each.

string

• Alias for System.String: The keyword string is an alias in C# for the .NET System.String class.
• Preferred for C# Code: In most cases, string is preferred when writing C# code because it’s more readable and familiar to those who work primarily with C#.
• Consistent with Other C# Aliases: Using string keeps your code consistent with other C# type aliases like int for System.Int32, bool for System.Boolean, etc.

Example:

string firstName = "John";
string lastName = "Doe";

String

• Full Name of the System.String Class: String refers to the actual System.String class in the .NET framework.
• Use in Frameworks and Libraries: You might see String used in more framework-level code, such as in .NET libraries or when you want to emphasize that you are working with the System.String class specifically.
• Static Methods and Constants: Sometimes, String is used when accessing static methods and constants defined in the System.String class, like String.Format or String.Empty.

Example:

String firstName = "John";
String lastName = "Doe";
string fullName = String.Concat(firstName, " ", lastName);

When to Use Which

• Consistency: It is generally recommended to use string in your C# code for consistency and readability.
• Clarity: Use String if you want to be explicit that you are referring to the .NET System.String class, especially in framework or library code.
• Accessing Static Members: Use String when accessing static methods or properties, as it can make the code slightly clearer.

Example Comparison

Using string:

public class Example
{
    public string GetGreeting(string name)
    {
        return "Hello, " + name;
    }
}

Using String:

using System;

public class Example
{
    public String GetGreeting(String name)
    {
        return "Hello, " + name;
    }
}

Summary

• string:

  • Alias for System.String.
  • Preferred for general use in C# code.
  • Enhances readability and consistency with other type aliases.

• String:

  • Full name of the System.String class.
  • Useful in framework-level code or when you want to be explicit.
  • Often used when accessing static members of the System.String class.

By understanding the nuances between string and String, you can write more consistent and readable C# code. For more in-depth knowledge and practical examples, consider exploring Grokking the Coding Interview on DesignGurus.io, which offers comprehensive courses on essential coding and interview techniques.