CODEWITHSUNDEEP
c#regex
Tono Nam
Tono Nam

Reputation: 36070

Extract string that is between string X and string Y

There is a similar question in here. In that question X happens to be ( and Y happened to be ). I am looking for something like

   public string GetStringBetweenStrings(string Source, string leftString, string rightString)
   {

       // implementation 
      Return middlePart;
   }

So that when I call that method as:

   var test = GetStringBetweenStrings("Hello World this is a test","World","test");

   // then test = " this is a ";

how can I build that function

Upvotes: 1

Views: 227

Answers (4)

yamen
yamen

Reputation: 15618

In the same linked question, you have a more flexible answer that works for all strings, modified here:

public string GetStringBetweenStrings(string source, string leftString, string rightString)
{
    int start = source.IndexOf(leftString); // assume != -1
    int end = source.IndexOf(rightString);  // assume != -1 and >= start
    if (start == -1 || end == -1 || end < start) return String.Empty;
    return source.Substring(start + leftString.Length, end - start - rightString.Length - 1)
}

This assumes that both strings are contained in the source string. What behaviour do you want if either one isn't? Or if start is after end?

Obligatory regex version as per @Jack but updated into function:

public string GetStringBetweenStrings(string source, string leftString, string rightString)
{
    return Regex.Match(source, String.Format(@"(?<={0})(.*)(?={1})", 
                       Regex.Escape(leftString),
                       Regex.Escape(rightString)))
                       .Captures[0].Value;
}

Upvotes: 2

Guvante
Guvante

Reputation: 19231

IndexOf is the most straight forward. Make sure you offset the start to past the first string. I also added some (untested) code to handle if left/right could overlap.

public string GetStringBetweenStrings(string Source, string leftString, string rightString)
{
   var left = Source.IndexOf(leftString);
   var right = Source.IndexOf(rightString);
   while (right > -1 && left + leftString.Length >= right)
   {
       right = Source.IndexOf(rightString, right + 1);
   }
   if (left > -1 || right > -1 || left < right)
       return null;
   var start = left + leftString.Length;
   var end = right;
   return Source.Substring(start, end - start);
}

Upvotes: 0

Jack
Jack

Reputation: 5768

(?<=World).*(?=test)

http://regexr.com?30ph4

Here's a regex solution. Replace World and test with your string variables when building the regex pattern.

Upvotes: 1

coffee_machine
coffee_machine

Reputation: 1223

Use the IndexOf function to locate the two strings. Then use SubString to extract what you need.

Upvotes: 0

Related Questions