C# Error CS8148 – ‘{0}’ must match by reference return of overridden member ‘{1}’

C# Error

CS8148 – ‘{0}’ must match by reference return of overridden member ‘{1}’

Reason for the Error & Solution

must match by reference return of overridden member

Example

The following sample generates CS8148:

// CS8148.cs (11,29)

public class Base
{
    public virtual int GetNumber() { return 0; }
}

public class Derived : Base
{
    private int number;

    public override ref int GetNumber() { return ref number; }
}

To correct this error

Ensuring that base members that return by value are implemented by members that do not return by reference corrects this error:

public class Base
{
    public virtual int GetNumber() { return 0; }
}

public class Derived : Base
{
    private int number;

    public override int GetNumber() { return number; }
}