c# - How to skip lines while reading in a file using compact framework 3.5 -

i have windows form app have rewritten using compact framework 3.5. in original app had block of code used read in file , skip first 4 lines.

here code block works fine:

var openfile = file.opentext(fullfilename);             var fileempty = openfile.readline();             if (fileempty != null)             {                 var lines = file.readalllines(fullfilename).skip(4); //will skip first 4 rewrite file                 openfile.close();//close reading of file                 file.writealllines(fullfilename, lines); //reopen file write lines                 openfile.close();//close rewriting of file             }  

i had rewrite above code in since can't used in compact framework.

here code:

var openfile = file.opentext(fullfilename);             var fileempty = openfile.readline();             if (fileempty != null)             {                 var sb = new stringbuilder();                 using (var sr = new streamreader(fullfilename))                 {                     string line1;                     // read , display lines file until end of                      // file reached.                     while ((line1 = sr.readline().skip(4).tostring()) != null) //will skip first 4 rewrite file                     {                         sb.appendline(line1);                     }                 } 

however when run above, receive error on (while ((line1 = sr.readline().skip(4).tostring()) != null)) argumentnullexception unhandled , value can not null.

can please tell me how can in compact framework?

since sr.readline() returns single string, going skip first 4 characters in string, return rest character array, , call tostring() on it... not want.

sr.readline().skip(4).tostring() 

the reason you're getting argumentnullexception because sr.readline() returns null string, , when try skip first 4 characters of null string, throws, can see looking @ implementation skip():

public static ienumerable<tsource> skip<tsource>(this ienumerable<tsource> source, int count) {     if (source == null)         throw new argumentnullexception("source");      return skipiterator<tsource>(source, count); } 

keeping of code same, read first few lines , nothing them (assuming you'll have @ least 4 lines in file).

using (var sr = new streamreader(fullfilename)) {     // read first 4 lines nothing them; basically, skip them     (int i=0; i<4; i++)         sr.readline();      string line1;      while ((line1 = sr.readline()) != null)     {         sb.appendline(line1);     } }