When to use String and StringBuilder in C#

In C#, String and StringBuilder are both used for handling strings, but they are suitable for different scenarios due to their underlying implementations and performance characteristics.

When to Use String

1. Immutable Operations: Use String when you need to perform operations that do not involve frequent or complex modifications. Since String is immutable, any modification (e.g., concatenation, insertion, deletion) results in the creation of a new string object, which can be inefficient for heavy modifications.
2. Simple Concatenations - When dealing with a small number of concatenations or string manipulations, String is more straightforward and readable.
3. String Literals and Constants - Use String for fixed values, literals, or when working with simple string constants.

Example

string greeting = "Hello";
string name = "Rohatash";
string message = greeting + ", " + name + "!"; // Simple concatenation
Console.WriteLine(message);

When to Use StringBuilder

1. Frequent or Complex Modifications- Use StringBuilder when you need to perform a large number of modifications to a string, such as concatenations in a loop, appending, inserting, or removing substrings. StringBuilder is designed for such scenarios and provides better performance because it allows for in-place modifications.
2. Performance Considerations - When performance is a concern, especially in scenarios where strings are modified multiple times, StringBuilder is more efficient as it reduces the overhead of creating multiple string instances.

Example

StringBuilder sb = new StringBuilder();
for (int i = 0; i = 1000; i++)
{
    sb.Append("Line");
    sb.Append(i);
    sb.AppendLine();
}
string result = sb.ToString();
Console.WriteLine(result);