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C# String Immutability

In C#, strings are immutable, meaning that once a string is created, it cannot be changed. Any operation that appears to modify a string actually creates a new string object.

Key Topics

1. Understanding Immutability

Example: String Modification

string original = "Hello";
string modified = original + " World";
Console.WriteLine(original); // Outputs: Hello
Console.WriteLine(modified); // Outputs: Hello World

In this example, original remains unchanged, and a new string modified is created.

2. Effects on Performance

Because strings are immutable, concatenating strings in a loop can lead to performance issues due to the creation of multiple string objects.

Example: Inefficient String Concatenation

string result = "";
for(int i = 0; i < 1000; i++)
{
    result += "*";
}

3. Using StringBuilder as an Alternative

The StringBuilder class provides a mutable string object, which is more efficient for frequent modifications.

Example: Efficient String Concatenation with StringBuilder

using System.Text;

StringBuilder sb = new StringBuilder();
for(int i = 0; i < 1000; i++)
{
    sb.Append("*");
}
string result = sb.ToString();

Key Takeaways

  • Strings are immutable; operations create new string instances.
  • Frequent string modifications can lead to performance issues.
  • Use StringBuilder for efficient string manipulation in loops.
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