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up vote 1 down vote favorite

I have been searching for about an hour and simply can't find any solutions to this. I want each row from my .txt-file to be added to my list as long as it starts with the same number. The problem lies within "line.Substring(0, 1)" and i dont know how to solve it. Perhaps you understand what i want to acheive.

        using (StreamReader file = new StreamReader(schedulePathDays))
        {
            string line;
            while ((line.Substring(0, 1) = file.ReadLine()) == thisDay.ToString())
            {
                exercisesRow.Add(line);
            }
        }
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Why not string.StartsWith()? – Lloyd 22 mins ago
line seems to be null... – Sebastian Piu 22 mins ago
(line.Substring(0, 1) = file.ReadLine()) is wrong. Did you mean (file.ReadLine().Substring(0, 1))? – Nolonar 22 mins ago
@TimSchmelter He's calling line.SubString before even assigning anything to line. – Nolonar 16 mins ago

3 Answers

up vote 5 down vote

You can use ReadLines and then use LINQ to filter:

var result = File.ReadLines("yourPath")
                 .Where(line => line.StartsWith("1"));

ReadLines is deferred execution so it can work in large text file.

Edit: To map with your code, replace your code with below:

exercisesRow = File.ReadLines(schedulePathDays)
                   .Where(line => line.StartsWith(thisDay.ToString()))
                   .ToList();
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2  
+1 for mentioning deferred execution – Nolonar 19 mins ago
Im very new to C# and therefor i don't know how to use the code you just posted. Could you post how my code would look with your code included? thanks! – Arvin Ashrafi 14 mins ago
@ArvinAshrafi: Edited my answer – Cuong Le 11 mins ago
@ArvinAshrafi Keep in mind, that you shouldn't blindly copy-paste other people's code. Try to understand the code first. For instance: File should actually be file (lower-case) and StartWith should be StartsWith (with 's' in between). – Nolonar 9 mins ago
@Nolonar: thanks for pointing out StartsWith :), but File should not change to file since ReadLines is static method – Cuong Le 8 mins ago
up vote 0 down vote

Your syntax doesn't make sense. You might want something like:

file.ReadLine().Substring(0,1)==thisDay.ToSTring()

I think this is what you wanted to write though Cuong Le's answer is probably a lot nicer (except needing parameterisation).

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up vote 0 down vote

Your Substring(0,1) is in the wrong place. It should come after line is assigned.

//Altnerately: (...).Substring(0,1) instead of (...)[0]
while((line = file.ReadLine())[0] == thisDay.ToString()[0]){
    //code
}

It makes no sense to ask try to assign the result of the Substring method.

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