C# detect if line in file exists, before attempting to read substring

Question

I want to read settings from a text file.

string MySettingsFile = "Settings.txt";

Normally, the file would have 4 lines.

SettingA:Alpha1
SettingB:Bravo2
SettingC:Charlie1
SettingD:Delta6

I want to get each line in it's own variable, like this :

string MyAlpa = "Alpha1";
string MyBravo = "Bravo2";
string MyCharlie = "Charlie1";
string MyDelta = "Delta6";

Normally, I would just read the lines in a loop, reading each line and setting the string as I go. If, however, Line 4 is missing, and I am looking for the part of the line after the colon, I get an error if I check for it like this...

MyDelta = MyDeltaSubstring(MyDelta.LastIndexOf(':') + 1);

Is there a way to 'check for the existence of a specific line' before I attempt to get the SubString (so it doesn't get an error), like in a function separate that has try, catch, finally with return either the string I want or the word "Missing", if that line is missing (and then stop since there are no more lines)?

function DoesLineExist(int X, string myFile)
{
    string MyString;

    try ()
    {
        // read line X from file myFile
        // get everything AFTER the ":" and put it in MyString
        // ??? //
    }
    catch (ArgumentException null)
    {
        MyString = "Missing";
    }
    catch (ArgumentException e)
    {
        MyString = "Missing";
    }

    finally
    {
        MyString = ? // whatever we got From Line X (after ":")
    }
    return MyString; // only if line is missing
}

Is there a better way of doing this? ReadAllLines or something maybe?

Answer 1

You need to first verify that that line is exist or not and then again check that is line contains key/value pair of settings is exist and then project your key value pair into dictionary and then get each setting to your variable by its key name.

Here i create a console app for your demonstration purpose.

class Program
{
    static void Main(string[] args)
    {
        Dictionary<string, string> dictSettings = new Dictionary<string, string>();

        string MyAlpa = "";
        string MyBravo = "";
        string MyCharlie = "";
        string MyDelta = "";

        var lines = File.ReadAllLines(@"C:\Users\xxx\source\repos\ConsoleApp4\ConsoleApp4\Files\Sample.txt");
        for (var i = 0; i < lines.Length; i += 1)
        {
            var line = lines[i];
            //DoesLineExist(line);

            if (!string.IsNullOrEmpty(line) && line.Contains(":"))
            {
                string settingKey = line.Split(':')[0];
                string settingValue = line.Split(':')[1];
                dictSettings.Add(settingKey, settingValue);
            }
        }


        MyAlpa = dictSettings.ContainsKey("SettingA") ? dictSettings["SettingA"] : "";
        MyBravo = dictSettings.ContainsKey("SettingB") ? dictSettings["SettingB"] : "";
        MyCharlie = dictSettings.ContainsKey("SettingC") ? dictSettings["SettingC"] : "";
        MyDelta = dictSettings.ContainsKey("SettingD") ? dictSettings["SettingD"] : "";

        Console.WriteLine(MyAlpa);
        Console.WriteLine(MyBravo);
        Console.WriteLine(MyCharlie);
        Console.WriteLine(MyDelta);

        Console.ReadLine();
    }

    //private static void DoesLineExist(string line)
    //{
    //    if (!string.IsNullOrEmpty(line) && line.Contains(":"))
    //    {
    //        string settingKey = line.Split(':')[0];
    //        string settingValue = line.Split(':')[1];
    //        dictSettings.Add(settingKey, settingValue);
    //    }
    //}
}

Input:

SettingA:Alpha1
SettingB:Bravo2
SettingC:Charlie1

Output:

Input:

SettingA:Alpha1
SettingC:Charlie1
SettingD:

Output: