Compiler Error CS8161

A static readonly field cannot be returned by writable reference

Example

The following sample generates CS8161:

// CS8161.cs (12,14)
public class Test
{
    public struct S1
    {
        public char x;
    }

    public static readonly char s1;

    ref char Test2()
    {
        return ref s1;
    }
}

To correct this error

To return the value of a static readonly field, refactor to return by value:

public class Test
{
    public struct S1
    {
        public char x;
    }

    public static readonly char s1;

    char Test2()
    {
        return s1;
    }
}