Why is .NET's String Immutable, While StringBuilder is Mutable?

The invariability of .NET String and the variability of StringBuilder: The reasons behind the design

Introduction:

.NET's String type has the key feature of invariance. In contrast, the StringBuilder class was introduced as a variable alternative. This article discusses the reasons behind this design decision.

The advantage of non -degeneration:

Thread security: The constant instance is essentially thread security, eliminating the risk of concurrent modification.

Compiler Optimization:
1. Unrealized allows the compiler to optimize, eliminates the problem of aliases, and allows residency and atomicization of the string word. Memory saving:
Objects can share the reference to the unchanged string, so as to save a lot of memory.
2. predictable behavior: Pass the constant string as a method parameter to ensure that its value remains unchanged during the execution of the method.
3. Clear concept: Non -change string follows the type of value of value, which is equal to the state -based rather than the logo.
Unchanged semantic relationship:
4. Some operations can logically lead to the new value, such as adding monthly or changing people's name to the date. Efficient replication:
The cloned constant string is fast and simple, because only reference is returned.
5. Internal state sharing: Unchanged objects can share the internal state, thereby reducing the cost of creating sub -range or sub -array.
6. Introduced StringBuilder to achieve variability:
7. Although there are many advantages of invariability, degeneration is still needed in some cases, such as dynamic constructing string or efficiently operating text. StringBuilder is introduced as a variable correspondence as String to meet these needs. It provides performance advantages by avoiding frequent creation and replication objects. Conclusion:
8. .NET String types were unsatisfactory. It was a thoughtful decision. It provided multiple advantages, including thread security, compiler optimization and predictable behavior. However, the introduction of the variable StringBuilder class supplements this design, which provides flexibility for the scene of dynamic string operation.

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