Search using BinaryWriter and BinaryReader Operation c#

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Hi,

I have some data like roll, name and mark. I have written these to a file. Like

C#

FileStream fs = new FileStream("data.dat",FileMode.OpenOrCreate);
           BinaryWriter br = new BinaryWriter(fs);
           br.Write(Convert.ToInt32(textBox1.Text)); //Textbox1 for int roll
           br.Write(textBox2.Text);                  // Textbox2 for string name
           br.Write(Convert.ToInt32(textBox3.Text)); //Textbox3 for int mark
           fs.Flush();
           br.Flush();
           fs.Close();
           br.Close();

Can we write a new record like roll, name and merk in new line every time using BinaryWriter. Can we read new line every time using BinaryReader.
Now I have to search any record based on roll from that file using BinaryReader class . How can i enter a roll in textbox and search the record from file.

Thank you.

Posted 29-Oct-13 22:55pm

Brijesh Kr

Updated 29-Oct-13 23:28pm

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OriginalGriff · Answer 1 · 2013-10-29T23:10:00

Using that data, probably you can't - it's a very poor data format in that you don't know how long the string you are writing is - and you can only tell by taking the file size and subtracting the lengths of all the other bits and pieces you have added. And you can only read the final integer by first finding out how long the string is and reading or Seeking past it.

And your text implies that this will be one record of many, so you will not be able to easily work out where records begin and end at all!

I would suggest that you want to look at how you do this a bit more closely before you continue, and design a data format that will be more amenable to the searching.

Is this homework? If not there are things you can do to make it easier (like not faffing about with BinaryWriters...)

Fredrik Bornander · Answer 2 · 2013-10-29T23:11:00

To search a file written using BinaryReader you can sequentially read the elements in the same order they were written whilst checking some condition.

The below example show appending two items to a file and then trying to find one of them again using the string value as a condition:

C#

using System;
using System.IO;

namespace Stuff {

    class Program {

        private static void Append(int a, string b, int c) {
            using (var fs = new FileStream(@"C:\Temp\data.dat", FileMode.Append)) {
                using (var br = new BinaryWriter(fs)) {
                    br.Write(a);
                    br.Write(b);
                    br.Write(c);
                }
            }
        }

        private static bool TryFindString(string s, out int a, out int c) {
            a = 0;
            c = 0;
            using (var fs = new FileStream(@"C:\Temp\data.dat", FileMode.Open)) {
                using (var br = new BinaryReader(fs)) {
                    while (fs.CanRead) {
                        // It is important to read all the values here in the order
                        // they were written, not just the search item.
                        a = br.ReadInt32();
                        var b = br.ReadString();
                        c = br.ReadInt32();

                        if (s == b)
                            return true;
                    }
                }
            }
            return false;
        }

        static void Main(string[] args) {
            Append(1, "A", 100);
            Append(2, "B", 200);

            int a, c;
            if (TryFindString("B", out a, out c)) {
                Console.WriteLine("Found string {0}, a={1} and b={2}", "B", a, c);
            }
        }
    }
}

Hope this helps,
Fredrik

Search using BinaryWriter and BinaryReader Operation c#

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