Why do I get the error "Unsafe code may only appear if compiling with /unsafe"?

Question

To use unsafe code blocks, the project has to be compiled with the /unsafe switch on.

Open the properties for the project, go to the Build tab and check the Allow unsafe code checkbox.

Here is a screenshot:

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Probably because you're using unsafe code.

Are you doing something with pointers or unmanaged assemblies somewhere?

Search your code for unsafe blocks or statements. These are only valid is compiled with /unsafe.

To use unsafe code blocks, open the properties for the project, go to the Build tab and check the Allow unsafe code checkbox, then compile and run.

class myclass
{
     public static void Main(string[] args)
     {
         unsafe
         {
             int iData = 10;
             int* pData = &iData;
             Console.WriteLine("Data is " + iData);
             Console.WriteLine("Address is " + (int)pData);
         }
     }
}

Output:

Data is 10
Address is 1831848