String[] index number from regex search

Question

I have a string[] that I search using regex and it returns a list of elements in my string[] that match what I searched for using regex. I would like to find the index number of the elements that are returned.

example:

string[] StringArray = {"aaa","bbb","ccc","ddd","eee"};

string find = "bbb";

List<string> FoundList = new List<string>();

foreach (string Block in StringArray)
{
if (System.Text.RegularExpressions.Regex.IsMatch(Block, find,
System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
FoundList.Add(Block);
}
else
{
//do nothing
}
}

string[] FoundArray = FoundList.ToArray();

it will create FoundArray = {"bbb"} and I wish to find int i such that

StringArray[i] = FoundArray[0]

is true and for senarios where FoundArray has multiple entries I plan to loop it. Any help would be much appreciated.

Amit Choudhary · Answer

perfect idea @vulpes you covered almost everything.. :) nice

Vulpes · Answer

Amit's idea of using a Dictionary will also give you a welding between the string and index. However, StringArray.IndexOf(Block), will always give you the same index, even if there are duplicates found so you'd need to modify his code to use a 'for' rather than a 'foreach' loop. The code for the Tuple approach would be: string[] StringArray = {"aaa","bbb","ccc","ddd","eee"}; string find = "bbb"; List > FoundList = new List >(); for(int i = 0; i { string Block = StringArray[i]; if (System.Text.RegularExpressions.Regex.IsMatch(Block, find, System.Text.RegularExpressions.RegexOptions.IgnoreCase)) { FoundList.Add(Tuple.Create(Block, i)); } } Tuple [] FoundArray = FoundList.ToArray(); Console.WriteLine(FoundArray[0].Item1); Console.WriteLine("{0} : {1}", FoundArray[0].Item2, StringArray[FoundArray[0].Item2]);

alec · Answer

I am using .NET 4 and the welding seems like a good idea as I need the computer to know the index number not me (sorry for not saying that) and your solution Amit seems a bit high brow for a beginner such as myself but it looks like a good one can you recommend any links to see how the solution works so I can try and understand it a bit better? Thank you

Amit Choudhary · Answer

use a Map or Dictionary to store the matched string found with its associated index. you can find the index of element by StringArray.IndexOf(Block) so you code would look like Dictionary foundStrings=new Dictionary (); and inside the loop write below code with the FoundList.Add(Block) foundStrings.Add(StringArray.IndexOf(Block), Block); now you have everything you want..so you can loop through the dictionary and match the FoundList array Element..

Vulpes · Answer

There are several ways to do this. Here's a simple one: string[] StringArray = {"aaa","bbb","ccc","ddd","eee"}; string find = "bbb"; List FoundList = new List (); List IndicesList = new List (); for(int i = 0; i { string Block = StringArray[i]; if (System.Text.RegularExpressions.Regex.IsMatch(Block, find, System.Text.RegularExpressions.RegexOptions.IgnoreCase)) { FoundList.Add(Block); IndicesList.Add(i); } } string[] FoundArray = FoundList.ToArray(); int[] IndicesArray = IndicesList.ToArray(); Console.WriteLine(FoundArray[0]); // bbb Console.WriteLine("{0} : {1}", IndicesArray[0], StringArray[IndicesArray[0]]); // 1 : bbb If you're using .NET 4.0, you could also use a List > to weld the found string and its index together.