如何在C＃中获取子字符串的值

Question

I want to getBack param from a string as :

Lorem ipsum dolor sit amet, %param% consectetur adipiscing elit. Ut placerat risus vitae augue vestibulum imperdiet. Nullam ac urna pellentesque purus hendrerit convallis. Morbi bibendum augue sed mi faucibus, sit amet scelerisque augue interdum. Aenean iaculis lacus ut sapien imperdiet mollis.

I tried to use :

texte.Split(new char[] {'%'});

It just split my text, how can I split with a start char and an end char ?

Answer 1

Following regex should help:

var regex = new Regex(@"%(?<param>.*?)%");
var match = regex.Match("Lorem ipsum dolor sit amet, %param% consectetur adipiscing elit. Ut placerat risus vitae augue vestibulum imperdiet. Nullam ac urna pellentesque purus hendrerit convallis. Morbi bibendum augue sed mi faucibus, sit amet scelerisque augue interdum. Aenean iaculis lacus ut sapien imperdiet mollis.");
if(match.Success)
{
    string result = match.Groups["param"].Value;
}

If there are multiple matches, following code will help:

string subject = "Lorem ipsum dolor sit amet, %param% consectetur %454% adipiscing elit. Ut placerat risus vitae augue vestibulum imperdiet. Nullam ac urna pellentesque purus hendrerit convallis. Morbi bibendum augue sed mi faucibus, sit amet scelerisque augue interdum. Aenean iaculis lacus ut sapien imperdiet mollis.";
var matches = Regex.Matches(subject, @"%(?<param>.*?)%");
foreach (Match match in matches)
{
    string result = match.Groups["param"].Value;
}

Answer 2

This should work ..

string str = "Lorem ipsum dolor sit amet, %param% consectetur adipiscing elit. Ut placerat risus vitae augue vestibulum imperdiet. Nullam ac urna pellentesque purus hendrerit convallis. Morbi bibendum augue sed mi faucibus, sit amet scelerisque augue interdum. Aenean iaculis lacus ut sapien imperdiet mollis.";
var param = str.Substring(str.IndexOf('%') + 1, str.IndexOf('%', (str.IndexOf('%') + 1)) - str.IndexOf('%') - 1);

Answer 3

You could do it using a foreach -loop although it might not be very efficient, depending on the length of your string.

string input = "Lorem ipsum dolor sit amet, %param% consectetur adipiscing elit. Ut placerat risus vitae augue vestibulum imperdiet. Nullam ac urna pellentesque purus hendrerit convallis. Morbi bibendum augue sed mi faucibus, sit amet scelerisque augue interdum. Aenean iaculis lacus ut sapien imperdiet mollis."
StringBuilder param = new StringBuilder();
List<string> params = new List<string>();
bool writingParam = false;

foreach(char c in input) {
  if(!writingParam && c == '%') {
    writingParam = true;
  }
  else if(writingParam) {
    if(c != '%') {
      param.Append(c);
    }
    else {
      params.Add(param.ToString());
      param = new StringBuilder();
      writingParam = false;
    }
  }
}

You will end up with at list of strings containing all strings enclosed in % .

Answer 4

If there is only a single %param% in the string that you can find it using indexOf and lastIndexOf

int len = input.Length;
int pos1 = input.IndexOf("%");
int pos2 = input.LastIndexOf("%");

string response = "";
if (pos1 != -1 && pos2 != -1 && (pos2 >= pos1))
{
    response = s.Substring(pos1 + start.Length, pos2 - pos1 - start.Length);
}