How to declare a public string within a while loop (C#)

I am currently trying to declare a public string within a while loop, as I would like to use it (the string) in other methods

The string in question is "s"

private void CheckLog()
{开发者_开发技巧
    bool _found;
    while (true)
    {
        _found = false;
        Thread.Sleep(5000);
        if (!System.IO.File.Exists("Command.bat")) continue;
        using (System.IO.StreamReader sr = System.IO.File.OpenText("Command.bat"))
        {
            string s = "";
            while ((s = sr.ReadLine()) != null)
            {
                if (s.Contains("mp4:production/CATCHUP/"))
                {
                    _found = true;
                    break;
                }
            }
        }
    }
}

you can't declare public string inside the method. Try this:

string s = "";
private void CheckLog()
{
    bool _found;
    while (true)
    {
        _found = false;
        Thread.Sleep(5000);
        if (!System.IO.File.Exists("Command.bat")) continue;
        using (System.IO.StreamReader sr = System.IO.File.OpenText("Command.bat"))
        {
            //s = "VALUE";
            while ((s = sr.ReadLine()) != null)
            {
                if (s.Contains("mp4:production/CATCHUP/"))
                {
                    _found = true;
                    break;
                }
            }
        }
    }
}

You should create a global variable and assign that instead for example

public class MyClass
{
    public string s;
    private void CheckLog() { ... }
}

In any method you might use it remember to check if s.IsNullOrEmpty() to avoid getting a NullPointerException (also I'm assuming that the string should contain something).

Better pass the string as by-ref argument to function, or return it from the function. Declaring it as member doesn't seem to be a good idea.

public string CheckLog(){}