unsafe (C# Reference)

The unsafe keyword denotes an unsafe context, which is required for any operation involving pointers. For more information, see Unsafe Code and Pointers (C# Programming Guide).

You can use the unsafe modifier in the declaration of a type or a member. The entire textual extent of the type or member is therefore considered an unsafe context. For example, the following is a method declared with the unsafe modifier:

unsafe static void FastCopy(byte[] src, byte[] dst, int count)
{
 // Unsafe context: can use pointers here.
}

The scope of the unsafe context extends from the parameter list to the end of the method, so pointers can also be used in the parameter list:

unsafe static void FastCopy ( byte* ps, byte* pd, int count ) {...}

You can also use an unsafe block to enable the use of an unsafe code inside this block. For example:

unsafe
{
 // Unsafe context: can use pointers here.
}

To compile unsafe code, you must specify the /unsafe compiler option. Unsafe code is not verifiable by the common language runtime.

Example

 // compile with: /unsafe
 class UnsafeTest
 {
 // Unsafe method: takes pointer to int:
 unsafe static void SquarePtrParam(int* p)
 {
 *p *= *p;
 }
 unsafe static void Main()
 {
 int i = 5;
 // Unsafe method: uses address-of operator (&):
 SquarePtrParam(&i);
 Console.WriteLine(i);
 }
 }
 // Output: 25

C# Language Specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.

See Also

Reference

C# Keywords

fixed Statement (C# Reference)

Unsafe Code and Pointers (C# Programming Guide)

Fixed Size Buffers (C# Programming Guide)

Concepts

C# Programming Guide

Other Resources

C# Reference