Question

I have the following function in C#:

    public string getRowKey(string topic, string rk)
    {
        return string.Join("", from s in topic.Split('.')
                               select s.PadLeft(2, '0')).PadRight(4, '0') +
                    rk.Substring(4);
    }

I have a problem because if rk is null or equal to “” then the function is failing. Can someone explain how I can fix this. I am getting an error about index values. Note that if rk is null or “” then I just don’t want that last part with rk.Substring(4) added.

Answer 1

A simple use of ternary operator ?: and function string.IsNullOrEmpty(string) would suffice

public string getRowKey(string topic, string rk)
{
    return string.Join("", from s in topic.Split('.')
                           select s.PadLeft(2, '0')).PadRight(4, '0') +
    string.IsNullOrEmpty(rk) ? "": rk.Substring(4);
}