C# Error CS8174 – A declaration of a by-reference variable must have an initializer

C# Error

CS8174 – A declaration of a by-reference variable must have an initializer

Reason for the Error & Solution

A declaration of a by-reference variable must have an initializer

Example

The following sample generates CS8174:

// CS8174.cs (7,22)

class C
{
    void M()
    {
        int i = 0;
        for (ref int rx; i < 5; i++) { }
    }
}

To correct this error

Initializing the by-reference variable with a reference to a variable will correct this error:

class C
{
    void M()
    {
        int i = 0;
        for (ref int rx = ref i; i < 5; i++) { }
    }
}