csharp / expert
Snippet
Unsafe Accessors for Zero-Overhead Private Member Access
Introduced in C# 12, Unsafe Accessors allow code to access private members of other classes without the performance penalty of Reflection. By using the [UnsafeAccessor] attribute on an extern static method, the compiler generates a direct IL reference to the private field or method, making it as fast as a public access while bypassing visibility constraints.
snippet.csharp
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using System.Runtime.CompilerServices;public class DataBuffer {private int _secretId = 42;}public class Accessor {[UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_secretId")]public static extern ref int GetSecretId(DataBuffer buffer);}// Usagevar buffer = new DataBuffer();ref int id = ref Accessor.GetSecretId(buffer);id = 100; // Directly modifies private field
Breakdown
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[UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_secretId")]
Instructs the compiler to link this method to a private field named _secretId.
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public static extern ref int GetSecretId(DataBuffer buffer);
Defines an external method that returns a reference to the private integer field.
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ref int id = ref Accessor.GetSecretId(buffer);
Retrieves the reference, allowing direct modification of the private state.