When chaining a base constructor, how can I reuse initialization code in an overload

Question

Please see question embedded in comment below.

public class CustomException : Exception
{
    private readonly string _customField;

    public CustomException(string customField, string message)
        : base(message)
    {
        // What's the best way to reuse the customField initialization code in the
        // overloaded constructor? Something like this(customField)
    }

    public CustomException(string customField)
    {
        _customField = customField;
    }
}

I'm open to considering alternative implementations that reuse the base constructor and minimize initialization code. I'd like to keep the _customField readonly, which is not possible if I extract a separate initialization method.

Answer 1

public CustomException(string customField) : this(customField,"")
{
}