Question

simple question, I import a DLL function and the parameter are int*.
When I try to enter Method(0), I get an error which says: “int and int* can not convert”.

What is that meaning?

Answer 1

That is classic C notation for a pointer to an int. Whenever a type is followed by a *, it denotes that type as a pointer to that type. In C#, unlike in C, you must explicitly define functions as unsafe to use pointers, in addition to enabling unsafe code in your project properties. A pointer type is also not directly interchangeable with a concrete type, so the reference of a type must be taken first. To get a pointer to another type, such as an int, in C# (or C & C++ for that matter), you must use the dereference operator & (ampersand) in front of the variable you wish to get a pointer to:

unsafe
{
    int i = 5;
    int* p = &i;
    // Invoke with pointer to i
    Method(p);
}

‘Unsafe’ code C#

Below are some key articles on unsafe code and the use of pointers in C#.

• Unsafe contexts
• Pointer Types
• Fixed and movable variables
• Pointer conversions
• Pointers in expressions
• The ‘fixed’ statement
• Stack allocation
• Dynamic memory allocation