`+ =`的C#运算符重载？

public class CustomType
{
    public int Value { get; set; }

    public CustomType(int value)
    {
        Value = value;
    }

    public static CustomType operator +(CustomType c1, CustomType c2)
    {
        return new CustomType(c1.Value + c2.Value);
    }
}

public class CustomType
{
    public int Value { get; set; }

    public CustomType(int value)
    {
        Value = value;
    }

    public static implicit operator CustomType(int value)
    {
        return new CustomType(value);
    }

    public static implicit operator int(CustomType customType)
    {
        return customType.Value;
    }
}