在C＃中将字符串拆分为数组，然后循环

Question

I have Googled this a LOT but my C# skills are pretty terrible and I just can't see why this isn't working.

I have a string which comes from a session object, which I don't have any control over setting. The string contains some sentences separated by six underscores. eg:

Sentence number one______Sentence number two______Sentence number three etc

I want to split this string by the six underscores and return each item in the resultant array.

Here's the code I have:

string itemsPlanner = HttpContext.Current.Session["itemsPlanner"].ToString();

string[] arrItemsPlanner = itemsPlanner.Split(new string[] { "______" }, StringSplitOptions.None);

foreach (string i in arrItemsPlanner)
{
  newItemsPlanner += "debug1: " + i;  //This returns what looks like a number, as I'd expect, starting at zero and iterating by one each loop.
  int itemNumber;

  try
  {
    itemNumber = Convert.ToInt32(i);
    string sentence = arrItemsPlanner[itemNumber].ToString();
  }
  catch (FormatException e)
  {
    return "Input string is not a sequence of digits.";
  }
  catch (OverflowException e)
  {
    return "The number cannot fit in an Int32.";
  }
  finally 
  {
    return "Fail!"
  }
}

Whenever I run this, the session is being retreived successfully but the line which says: itemNumber = Convert.ToInt32(i); fails every time and I get an error saying "Input string is not a sequence of digits."

Can anyone point me in the right direction with this please?

Many thanks!

Answer 1

in your case i is not a number, it's the actual element in the array. A foreach loop has no iteration variable, you only have access to the actual element being iterated through i .

So first loop itareation i is Sentence number one , then Sentence number two .

If you want the number, you have to use a for loop instead.

So something like this

for( int i = 0; i < arrItemsPlanner.length; i++ ){
  //on first iteration here
  //i is 0
  //and arrItemsPlanner[i] id "Sentence number one"
}

Hope it helps.

Answer 2

If you just want to get each sentence and do something with it, this will do the trick:

string itemsPlanner = HttpContext.Current.Session["itemsPlanner"].ToString(); 
string[] arrItemsPlanner = itemsPlanner.Split("______"); 

foreach (string i in arrItemsPlanner) 
{ 
  // Do something with each sentence
}

You can split over a string as well as char (or char[]). In the foreach 'i' will be the value of the sentence, so you can concatenate it or process it or do whatever :)

If I've misunderstood, my apologies. I hope that helps :)

Answer 3

From your example i does not contain a valid integer number, thus Convert.ToInt32 fails. The foreach loop sets i with the current item in the sentences array, so basically i always contains one of the sentences in your main string. If you want i to be the index in the array, use a for loop.

Answer 4

Example from MSDN .

    string words = "This is a list of words______with a bit of punctuation" +
                   "______a tab character.";

    string [] split = words.Split(new Char [] {'_'}, StringSplitOptions.RemoveEmptyEntries);

    foreach (string s in split) {

        if (s.Trim() != "")
            Console.WriteLine(s);
    }

Answer 5

Do you need to trim your string before converting to a number? if thats not you may want to use Int32.tryParse()

Answer 6

In your sample code foreach (string i in arrItemsPlanner) 'i' will get the string value of arrItemsPlanner one by one. For exmaple on first iteration it will have 'Sentence number one' which is obviously not a vlid ont, hence your conversion failed.

Answer 7

i only contains one of the string fragment which will be : number one Sentence number two and Sentence number three . If you want it to contain an int representing ht index, use : 1) a for loop 2) an int defined before your foreach and increase it (myInt++) in the foreach code !