Myujth

I have a listview that is filled with computernames and usernames and a number(as string). I already created my own ListViewItemComparer using the IComparer interface. But it doesn´t sort the items correctly like how I want.
This is how it should sort the computers for example:
Computer-1
Computer-2
Computer-3
...
Computer-15

and this is how it sorts them:
Computer-1
Computer-10
Computer-11
...
Computer-2
Computer-3

The problem is that i can´t simply cut the "computer-" part out and compare the numbers that follows as this was just an example and the computernames can be everything(aaa393bbb333, ccccvvvv, 222hhhdh,Computer-01, Computer-02,....)

This is my code:

 private bool isNumeric(String pInput)
 
 int o;
 return int.TryParse(pInput, out o);
 

 public int Compare(object x, object y)
 
 ListViewItem itemX = x as ListViewItem;
 ListViewItem itemY = y as ListViewItem;
 //
 int returnVal = -1;
 if (itemX == null && itemY == null) returnVal = 0;
 else if (itemX == null) returnVal = -1;
 else if (itemY == null) returnVal = 1;
 else if (itemX.SubItems.Count - 1 < col && itemY.SubItems.Count - 1 < col) returnVal = 0;
 else if (itemX.SubItems.Count - 1 < col) returnVal = -1;
 else if (itemY.SubItems.Count - 1 < col) returnVal = 1;
 else if(isNumeric(itemX.SubItems[col].Text) && isNumeric(itemY.SubItems[col].Text))
 
 //used for number comparison
 int value1 = int.Parse(itemX.SubItems[col].Text);
 int value2 = int.Parse(itemY.SubItems[col].Text);
 if (value1 == value2) returnVal = 0;
 else if (value1 < value2) returnVal = -1;
 else if (value1 > value2) returnVal = 1;
 
 else returnVal = String.Compare(itemX.SubItems[col].Text, itemY.SubItems[col].Text);
 if (order == SortOrder.Descending)
 returnVal *= -1;
 return returnVal;
 

You could use the regex expression

(?<=D)(?=d)|(?<=d)(?=D)

to split the string into numbers and text.

string parts = Regex.Split(theString, @"(?<=D)(?=d)|(?<=d)(?=D)");

This yields alternately numbers and texts. How it works:

(?<=exp)pos Match any position pos following a prefix exp. 
pos(?=exp) Match any position pos preceding a suffix exp. 

So the regex means, split at a position between text and number or at a position between number and text where D stands for a non-digit character, d for a digit character and | for OR.

You will have to test whether the first part is a text or a number with

bool firstIsNumber = Char.IsDigit(parts[0][0]);

If the first part is a number, all parts at even indexes are numbers and all parts at odd indexes are texts and vice versa.

private static readonly Regex numTextSplitRegex =
 new Regex(@"(?<=D)(?=d)|(?<=d)(?=D)", RegexOptions.Compiled);

public int Compare(string x, string y)

 x = x ?? "";
 y = y ?? "";
 string xParts = numTextSplitRegex.Split(x);
 string yParts = numTextSplitRegex.Split(y);

 bool firstXIsNumber = xParts[0].Length > 0 && Char.IsDigit(xParts[0][0]);
 bool firstYIsNumber = yParts[0].Length > 0 && Char.IsDigit(yParts[0][0]);

 if (firstXIsNumber != firstYIsNumber) 
 return x.CompareTo(y);
 

 for (int i = 0; i < Math.Min(xParts.Length, yParts.Length); i++) 
 int result;
 if (firstXIsNumber == (i % 2 == 0)) // Compare numbers.
 long a = Int64.Parse(xParts[i]);
 long b = Int64.Parse(yParts[i]);
 result = a.CompareTo(b);
 else // Compare texts.
 result = xParts[i].CompareTo(yParts[i]);
 
 if (result != 0) 
 return result;
 
 
 return xParts.Length.CompareTo(yParts.Length);