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How to Resolve Error "CS0214: Pointers and fixed size buffers may only be used in an unsafe context" in C#

The Compiler Error CS0214 is a security and safety restriction. The message reads: "Pointers and fixed size buffers may only be used in an unsafe context".

By default, C# is a Safe (Managed) language. The Common Language Runtime (CLR) manages memory allocation, garbage collection, and bounds checking to prevent common bugs like buffer overflows or memory leaks. Pointers (*, &, ->) and fixed-size buffers allow you to bypass these safety checks and manipulate memory directly. To prevent accidental memory corruption, C# requires you to explicitly opt-in to these features using the unsafe keyword.

This guide explains the two-step process required to enable pointer arithmetic in your project.

Understanding the Restriction​

Using pointers implies dealing with raw memory addresses. If you try to declare a pointer variable (int* ptr) or a fixed buffer (fixed int buffer[10]) without the proper setup, the compiler blocks it with CS0214.

Fixing this error requires two actions:

  1. Configuration: Tell the compiler (via .csproj) that this project is allowed to contain unsafe code.
  2. Code Context: Mark the specific region of code as unsafe.

Step 1: Enable Unsafe Code in Project Settings​

Even if you write the correct code syntax, you will get an error (often CS0227 followed by CS0214) if the project configuration forbids unsafe blocks.

Open your project file (.csproj) and add the <AllowUnsafeBlocks> tag inside a PropertyGroup.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    
    <!-- ✅ Correct: Enable unsafe code for the project -->
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>
</Project>

Option B: Visual Studio UI​

  1. Right-click your Project in Solution Explorer and select Properties.
  2. Go to the Build tab (or "Build > General" in newer versions).
  3. Check the box labeled Allow unsafe code.

Step 2: Use the unsafe Keyword​

Once the project allows it, you must explicitly mark the scope where pointers are used. You can mark a block, a method, or an entire class.

Example of error​

Trying to use pointers in a standard method.

public class PointerTest
{
    public void Run()
    {
        int number = 10;

        // ⛔️ Error CS0214: Pointers ... may only be used in an unsafe context
        // The syntax 'int*' and '&number' requires an unsafe scope.
        int* ptr = &number; 
        
        System.Console.WriteLine((int)ptr);
    }
}

Solution: Add 'unsafe' Modifier​

You can add the keyword to the method signature or wrap the logic in a block.

Option A: Unsafe Block (Scope limited)

public void Run()
{
    int number = 10;

    // ✅ Correct: Explicit unsafe block
    unsafe
    {
        int* ptr = &number;
        System.Console.WriteLine(*ptr);
    }
}

Option B: Unsafe Method

// ✅ Correct: The entire method is unsafe
public unsafe void Run()
{
    int number = 10;
    int* ptr = &number;
}

Scenario: Fixed Size Buffers in Structs​

Fixed size buffers are used primarily for Interop (communicating with C/C++ DLLs). They allow you to declare a C-style array directly inside a struct without the overhead of a managed array object.

Example of error​

public struct DataPacket
{
    // ⛔️ Error CS0214: Fixed size buffers may only be used in an unsafe context
    public fixed byte Header[4]; 
}

Solution​

The struct itself (or just the field) must be marked unsafe.

// ✅ Correct: Mark the struct as unsafe
public unsafe struct DataPacket
{
    public fixed byte Header[4];
    public int PayloadSize;
}
note

Accessing a fixed buffer (packet.Header[0]) also requires the calling code to be inside an unsafe context.

Conclusion​

CS0214 is a double-check system to prevent accidental memory management.

  1. Project Config: Ensure <AllowUnsafeBlocks>true</AllowUnsafeBlocks> is in your .csproj file.
  2. Code Context: Add the unsafe keyword to the class, method, or code block { ... } where you use pointers.
  3. Use Sparingly: Only use unsafe code when interacting with native APIs or optimizing critical performance hotspots.

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