Question

Hi i was trying to filter a large of text file using Regex.Split with about more than 20 of string patterns i need to use but the outcome is not correct and there are so many empty strings.

below is my code

string[] tmp = Regex.Split(originalString, @"(LINE|3DFACE|3DSOLID|ARC|ATTDEF|ATTRIB|BODY|CIRCLE|DIMENSION|ELLIPSE|HATCH|HELIX|IMAGE|INSERT|LEADER|LIGHT||LWPOLYLINE|MLINE|MLEADER|MLEADERSTYLE|MTEXT|OLEFRAME|OLE2FRAME|POINT|POLYLINE|RAY|REGION|SECTION|SEQEND|SHAPE|SOLID|SPLINE|SUN|SURFACE|TABLE|TEXT|TOLERANCE|TRACE|UNDERLAY|VERTEX|VIEWPORT|WIPEOUT|XLINE)");

if i only use about 5 of them then the outcome is able to do exactly as i need, is there any limit for regex.split for string patterns?

EDIT 1

THANKS TO @MRAB

here is the code for actually running working and right output

        string fileName = textBox1.Text;
        var stopwatch = new System.Diagnostics.Stopwatch();
        stopwatch.Start();
        TextReader sr = new StreamReader(fileName);
        string originalString = sr.ReadToEnd();
        sr.Close();
        string[] tmp = Regex.Split(originalString, @"(3DFACE|3DSOLID|ACAD_PROXY_ENTITIY|ARC|ATTDEF|ATTRIB|BODY|CIRCLE|DIMENSION|ELLIPSE|HATCH|HELIX|IMAGE|INSERT|LEADER|LIGHT|LWPOLYLINE|MLINE|MLEADERSTYLE|MLEADER|MTEXT|OLEFRAME|OLE2FRAME|POINT|POLYLINE|RAY|REGION|SEQEND|SHAPE|SOLID|SPLINE|SUN|SURFACE|TABLE|TEXT|TOLERANCE|TRACE|UNDERLAY|VERTEX|VIEWPORT|WIPEOUT|XLINE|LINE)");
        List<string> result = new List<string>();


        for (var i = 1; i < tmp.Count() - 1; i += 2)
        {

            result.Add(tmp[i] + tmp[i + 1]);
        }

Answer 1

You’re using the static Split method of the Regex class. There’s also a Split method on Regex instances, for example:

new Regex(@"(LINE|3DFACE|3DSOLID)").Split(originalString, 5, 0);

Your code contains this in the regex:

"LIGHT||LWPOLYLINE"

which looks like a mistake to me.

You should also note that when you have a regex like this:

"MLEADER|MLEADERSTYLE"

and a string like this:

"MLEADERSTYLE"

it will match "MLEADER" because that occurs earlier in a regex. Where a short literal occurs as a prefix of a longer literal, put the longer one earlier.