c# getting a string within another string

Question

i have a string like this:

 some_string = "A simple demo of SMS text messaging.\r\n+CMGW: 3216\r\n\r\nOK\r\n\"

im coming from vb.net and i need to know in c#, if i know the position of CMGW, how do i get "3216" out of there?

i know that my start should be the position of CMGW + 6, but how do i make it stop as soon as it finds "\\r" ??

again, my end result should be 3216

thank you!

Answer 1

Find the index of \\r from the start of where you're interested in, and use the Substring overload which takes a length :

// Production code: add validation here.
// (Check for each index being -1, meaning "not found")
int cmgwIndex = text.IndexOf("CMGW: ");

// Just a helper variable; makes the code below slightly prettier
int startIndex = cmgwIndex + 6;
int crIndex = text.IndexOf("\r", startIndex);

string middlePart = text.Substring(startIndex, crIndex - startIndex);

Answer 2

If you know the position of 3216 then you can just do the following

string inner = some_string.SubString(positionOfCmgw+6,4);

This code will take the substring of some_string starting at the given position and only taking 4 characters.

If you want to be more general you could do the following

int start = positionOfCmgw+6;
int endIndex = some_string.IndexOf('\r', start);
int length = endIndex - start;
string inner = some_string.SubString(start, length);

Answer 3

One option would be to start from your known index and read characters until you hit a non-numeric value. Not the most robust solution, but it will work if you know your input's always going to look like this (ie, no decimal points or other non-numeric characters within the numeric part of the string).

Something like this:

public static int GetNumberAtIndex(this string text, int index)
{
    if (index < 0 || index >= text.Length)
        throw new ArgumentOutOfRangeException("index");

    var sb = new StringBuilder();

    for (int i = index; i < text.Length; ++i)
    {
        char c = text[i];
        if (!char.IsDigit(c))
            break;

        sb.Append(c);
    }

    if (sb.Length > 0)
        return int.Parse(sb.ToString());
    else
        throw new ArgumentException("Unable to read number at the specified index.");
}

Usage in your case would look like:

string some_string = @"A simple demo of SMS text messaging.\r\n+CMGW: 3216\r\n...";
int index = some_string.IndexOf("CMGW") + 6;
int value = some_string.GetNumberAtIndex(index);

Console.WriteLine(value);

Output:

3216

Answer 4

If you're looking to extract the number portion of 'CMGW: 3216' then a more reliable method would be to use regular expressions. That way you can look for the entire pattern, and not just the header.

 var  some_string = "A simple demo of SMS text messaging.\r\n+CMGW: 3216\r\n\r\nOK\r\n";
 var match = Regex.Match(some_string, @"CMGW\: (?<number>[0-9]+)", RegexOptions.Multiline);
 var number = match.Groups["number"].Value;

Answer 5

More general, if you don't know the start position of CMGW but the structure remains as before.

 String s;
    char[] separators = {'\r'};
    var parts = s.Split(separators);
    parts.Where(part => part.Contains("CMGW")).Single().Reverse().TakeWhile(c => c != ' ').Reverse();