Reading from a sequential file into an array of structs

Question

I have the following struct:

    public struct StudentDetails
    {
        public string unitCode; //eg CSC10208
        public string unitNumber; //unique identifier
        public string firstName; //first name
        public string lastName;// last or family name
        public int studentMark; //student mark
    }

Using that struct I wrote data into a sequential file. The data in the file is as follow:

ABC123
1
John
Doe
95
DCE433
3
Sherlock
Holmes
100
ASD768
5
Chuck
Norris
101

etc.

What's the best way to read the data from that file and load it into an array of structs?

@BrokenGlass: variable, because the first name and last name will vary in length — n1te, Aug 14 '11 at 05:26

sternr · Answer 1 · 2011-08-14T05:36:57.047

1

Initially I'de use some sort of Serialization to write to the file since it will also take care of the reading part as well.
But given the way you created the file, I'de use StreamReader and it's ReadLine() method - since you know what the order of the properties you wrote to the server a simple while:

string line = "";
while ((line = reader.ReadLine()) != null)
{
  YourStruct t = new YourStruct();
  t.unitCode = line;
  t.unitNumber = reader.ReadLine();
  ...
  resultArray.Add(t);
}
reader.Close(); reader.Dispose();

edited Aug 14 '11 at 05:36

answered Aug 14 '11 at 05:26

sternr

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The `(line = reader.ReadLine()) != null` condition in your while loop is going to throw that line away, as you don't do anything with it in the while loop. – Tim Aug 14 '11 at 05:33

score 1 · Accepted Answer · edited May 23 '17 at 09:59

Assuming your file is one value per line:

List<StudentDetails> studentList = new List<StudentDetails>();

using (StreamReader sr = new StreamReader(@"filename"))
{

    while (!sr.EndOfStream)
    {
        StudentDetails student;

        student.unitCode = sr.ReadLine();
        student.unitNumber = sr.ReadLine();
        student.firstName = sr.ReadLine();
        student.lastName = sr.ReadLine();
        student.studentMark = Convert.ToInt32(sr.ReadLine());

        studentList.Add(student);
    }

    StudentDetail[] studentArray = studentList.ToArray();

}

Note that this is not very robust - if there are not 5 lines for each student, you'll run into problems, or if the last student has less than 5 lines.

EDIT

Taking the lessons learned from your previous question Array of structs in C# regarding the need to override ToString() in your struct, the following might help to resolve your issue with printing the values:

In StudentDetails struct (taken from Nick Bradley's answer):

public override string ToString()
{
    return string.Format("{0}, {1}, {2}, {3}, {4}", unitCode,
           unitNumber, firstName, lastName, studentMark);
}

Then you could simply loop through the array:

for (int i = 0; i < studentArray.Length; i++)
{
    Console.WriteLine("Student #{0}:", i);
    Console.WriteLine(studentArray[i]);
    Console.WriteLine();
}

The code works but the studentArray doesn't print anything except CA4.Program.StudentDetails, Any ideas? — n1te, Aug 14 '11 at 06:23
Based on your previous question, it looks like you'll need to override the `ToString()` method in your struct. Can you post the code that's not performing properly? See my edited answer. — Tim, Aug 14 '11 at 06:35

Reading from a sequential file into an array of structs

2 Answers2