C# Error CS8166 – Cannot return a parameter by reference ‘{0}’ because it is not a ref parameter

C# Error

CS8166 – Cannot return a parameter by reference ‘{0}’ because it is not a ref parameter

Reason for the Error & Solution

Cannot return a parameter by reference because it is not a ref parameter

Example

The following sample generates CS8166:

// CS8166.cs (11,20)

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

    ref char Test1(char arg1, S1 arg2)
    {
        return ref arg1;
    }
}

To correct this error

To return a parameter that is not passed by reference, refactoring to use return by value will correct this error:

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

    char Test1(char arg1, S1 arg2)
    {
        return arg1;
    }
}