Question

I’m having problems with the substring method, getting this error.

“Index and length must refer to a location within the string.”
“Parameter name: length”

string[] nombre = item.Split(new char[]{' '});
this.listBox5.Items.Add(nombre[0].Substring(0,2).ToUpper()+nombre[1].Substring(0,1));

Answer 1

It means that the values you are passing to Substring are not valid for the string they are being called on. For example:

string s = "hello";

string x = s.Substring(0, 1); // <-- This is fine (returns "h")
string y = s.Substring(1, 3); // <-- Also fine (returns "ell")
string z = s.Substring(5, 3); // <-- Throws an exception because 5 is passed
                              //     the end of 's' (which only has 5 characters)

As an aside, I see this a lot:

item.Split(new char[]{' '})

I think people are confused by the signature of the Split method. The following is sufficient:

item.Split(' ')