how to search for a string in text file in C#

Question

I am working on text file..i want to know how to search for a string in text file and then perform the operations on that string.I have written a code but there is some problem with " if condition ",when the particular string comes,the control skips to the next line..it doesnot perform any operation on that string.. Below is the line from text file from which i am trying to find "MerchantNo:105838015" and then performing Substring operation on it to get only the number..There is a space in between the line.. MERCHANTNO:105838015 AGENT CODE 00913

And this is the code:

    StreamReader sr = new StreamReader(fldr);
        string line = null;

        while ((line = sr.ReadLine()) != null)
        {
            str = line.Trim().Split(' ');
            for (int i = 0; i < str.Length; i++)
            {
                if (str.ToString().ToUpper().Contains("MERCHANTNO:105838015"))
                {
                        //str = line.Split(' ');
                        string MNo1 = line.Substring(15, 23);
                        MNo = Convert.ToInt32(MNo1.ToString());
                }
                break;

            }

            //MessageBox.Show("Line is:" +line);
        }

        MessageBox.Show("MerchantNo is:" +MNo);

Please do say me what i have to do??

Answer 1

I suspect that this is the problem:

if (str.ToString()...)

You're calling ToString on a string array. I suspect you meant:

if (str[i].ToUpper().Contains(...))

Having said that, it's not clear why you're then using the line for a substring - or why you're calling MNo1.ToString() when MNo1 is already a string...

I would also recommend that you use:

if (str[i].IndexOf("MERCHANTNO:105838015",
                   StringComparison.CurrentCultureIgnoreCase) > -1)

(or something similar, depending on what culture you want to use) rather than upper-casing each part.

You should also consider using a foreach loop instead of a for loop:

foreach (string part in line.Trim().Split(' '))
{
    if (part.IndexOf(...) > -1)
    {
        ...
    }
}

Answer 2

I think if you use Regular Expression you can solve your problem quickly. First of all read whole file in a variable and then apply your Regular Expression to that.

You can use grouping in your expression to get the number separately like below:

        int number = 0;
        using (var sr = new StreamReader(fileName))
        {
            string fileContent = sr.ReadToEnd();
            Regex regex = new Regex(@"(?<=.*MERCHANTNO:)(?<number>\d*)");
            var match = regex.Match(fileContent);
            if (match.Groups["number"].Success)
            {
                number = Convert.ToInt32(match.Groups["number"].Value);
            }
        }

        MessageBox.Show("MerchantNo is:" + number);

Answer 3

It's a bit confusing what this code supposed to do, but I guess you wanna make sure if the file contains this merchantno ? You should use regex instead of substring juggling.

With text file:

MERCHANTNO:10583218015 AGENT CODE 00913
MERCHANO: 10421523838015 AGENT CODE 00913
Some teeeext MERCHANTNO:105838015 AGENT CODE 00913
Some text salalala ME

And code:

var regi = new Regex(@"MERCHANTNO:\s*([0-9]*)");
string need = "105838015";
bool found = false;

using (StreamReader reader = new StreamReader("file.txt"))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        var match = regi.Match(line);
        if (match.Groups.Count == 2)
        {
            if (match.Groups[1].Value == need)
            {
                found = true;
                break;
            }
        }
    }
}

Console.WriteLine("Found: {0}", found);

Maybe this is what you want? Fixme.

(string testing for value, to avoid 012 == 12 int parsing)