Compiler Error CS8160

A readonly field cannot be returned by writable reference

Example

The following sample generates CS8160:

// CS8160.cs (8,20)

class Program
{
    readonly int i = 0;

    ref int M()
    {
        return ref i;
    }
}

To correct this error

To return a readonly field, refactor to return by value:

class Program
{
    readonly int i = 0;

    int M()
    {
        return i;
    }
}