Is C#'s Handling of Uninitialized Variables Predictable?

Is the behavior of uninitialized variables consistent in C#?

The C# language specification mandates that variables be assigned before using them (section 5.3). This is a common practice in other languages ​​like C and unmanaged C due to potential memory issues. However, uninitialized variables behave differently in C#.

Is uninitialized variable null in C#?

Contrary to expectations, uninitialized reference types in C# will always evaluate to null. They do not retain values ​​from previous function calls or random values.

Pre-assigned variables

Some variables, such as fields and array elements, are automatically assigned default values ​​during initialization (null for reference types, zero for numeric types, etc.).

Not initialized but initialized

Surprisingly, local variables have initial assignment in C# even if they are not explicitly initialized. The common language runtime (CLR) ensures that all local variables are forced to zero, resulting in predictable default values.

Compiler enforcement

Despite pre-assignment, in order to prevent potential errors, local variables must still be assigned explicitly before using them in C#. The compiler enforces this rule, so garbage uninitialized state cannot be observed.

Conclusion

Although uninitialized variables in C# are always initially assigned a default value, it is best to avoid using them to prevent any potential errors. The compiler's enforcement of this rule ensures the reliability of C# code.

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