expected.cs

class MyClass
{
    private int oAsInt32;

    void Method(object o)
    {
        var oAsInt32 = o as int?;
        if (oAsInt32 != null)
        {
            Console.Write(oAsInt32.Value);
        } else {
            Console.Write(this.oAsInt32);
        }
    }
}

original.cs

class MyClass
{
    private int oAsInt32;

    void Method(object o)
    {
        if (o is int)
        {
            Console.Write((int) o);
        } else {
            Console.Write(oAsInt32);
        }
    }
}

result.cs

class MyClass
{
    private int oAsInt32;

    void Method(object o)
    {
        var oAsInt32 = o as int?;
        if (oAsInt32 != null)
        {
            Console.Write(oAsInt32.Value);
        } else {
            Console.Write(oAsInt32);
        }
    }
}