c# - Compare and Remove List Items using For Loop -


i have download list , exclude list.

i want keep file2.zip using loop.

however loop doesn't work correctly , keeps both file2.zip , file4.zip.

http://rextester.com/uwct32568

this example code want apply larger project.

i not want use download = download.except(excluded).tolist(); in case.

http://rextester.com/hbqzpc42707

list<string> download = new list<string>(); download.add("file1.zip"); download.add("file2.zip"); download.add("file3.zip"); download.add("file4.zip"); download.add("file5.zip");  list<string> excluded = new list<string>(); excluded.add("file1.zip"); // keep file2.zip excluded.add("file3.zip"); excluded.add("file4.zip"); excluded.add("file5.zip");   // remove excluded files download list // int count = download.count();  (int = 0; < count; i++) {     // index out of range check     if (download.count() > )     {         // remove         if (excluded.contains(download[i]))         {             download.removeat(i);             download.trimexcess();         }     } }   // display new download list // download.foreach(x=>console.writeline(x));

  1. when removing, loop backward:
  2. use hashset<string> more efficient finding item at

implementation:

 // items remove: excluded.contains(item) more efficient if excluded hashset<t>  hashset<string> excluded = new hashset<string>() {    "file1.zip",    "file3.zip",    "file4.zip",    "file5.zip",    };   (int = download.count - 1; >= 0; --i)    if (excluded.contains(download[i])) // shall remove i-th item?      download.removeat(i);             // if yes, remove    // if want trim list, not within loop,   // remove required items , trim (once!) list  download.trimexcess(); // not necessary, possible

edit: in (rare) cases when have to loop forward (e.g. if have remove items in order created) loop is

 (int = 0; < download.count;)   // please, notice, no increment here    if (excluded.contains(download[i]))  // shall remove i-th item?      download.removeat(i)               // if yes, remove    else      += 1;                            // if no, inspect next item

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