Split a string of Number and characters

Question

I had a List liRoom which contains a alphanumeric and Alphabetic string For Example

List<string> liRoom = new List<string>() {"Room1","Room2","Room3",  
                                         "Room4","Hall","Room5","Assembly",  
                                         "Room6","Room7","Room8","Room9};

This List is of type Alphanumeric and Alphabetic so i want to take the max numeric value from this list of string.
I had tried to do it this way

var ss = new Regex("(?<Alpha>[a-zA-Z]+)(?<Numeric>[0-9]+)");  
List<int> liNumeric = new List<int>();  
foreach (string st in liRoom)  
{   
var varMatch = ss.Match(st);  
liNumeric.Add(Convert.ToInt16(varMatch.Groups["Numeric"].Value));   
}  
int MaxValue = liNumeric.Max();// Result Must be 9 from above Example.

And

 List<int> liNumeric = new List<int>();  
 foreach (string st in liRoom)  
 {   
   liNumeric.Add( int.Parse(new string(st.Where(char.IsDigit).ToArray())));   
 }  
 int MaxValue = liNumeric.Max();// Result Must be 9 from above Example.

But both shows error when st is Hall,Assembly
Help me How to do this.

Answer 1

there are few reasons you will get exception in your code. I'm adding few condition for those possible exceptions.

List<int> liNumeric = new List<int>();  
 foreach (string st in liRoom)  
 { 
   // int.Parse will fail if you don't have any digit in the input 
   if(st.Any(char.IsDigit))
   {
       liNumeric.Add(int.Parse(new string(st.Where(char.IsDigit).ToArray()))); 
   }

 }  
 if (liNumeric.Any()) //Max will fail if you don't have items in the liNumeric
 {
     int MaxValue = liNumeric.Max();
 }

Answer 2

Please try the following:

List<string> liRoom = new List<string>() {"Room1","Room2","Room3",  
                                         "Room4","Hall","Room5","Assembly",  
                                         "Room6","Room7","Room8","Room9"};


var re = new Regex(@"\d+");

int max = liRoom.Select(_ => re.Match(_))
                .Where(_ => _.Success)
                .Max( _ => int.Parse(_.Value));

/* 
   max = 9 
*/

Answer 3

You should add below in your code by checking whether match is success or not

if (varMatch.Success)
{
     liNumeric.Add(Convert.ToInt16(varMatch.Groups["Numeric"].Value));
}

Answer 4

You don't need foreach , it can be done with one statement:

int value = liRoom.Where(x => x.Any(char.IsDigit))
            .Select(x => Convert.ToInt32(new String(x.Where(char.IsDigit).ToArray())))
            .Max();

It seems odd but it's working. :)