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    <p>(note: this might seem an over-complicated solution, but I'm assuming that the source data is large (lots of rows), so loading it into a <code>List&lt;T&gt;</code> might not be feasible)</p> <p>The file reading would be done quite well with an iterator block... if the data is large, you only want to handle one row at a time, not a 2D array.</p> <p>This actually looks like a good fit for <a href="http://www.pobox.com/~skeet/csharp/miscutil/" rel="nofollow noreferrer">MiscUtil</a>'s PushLINQ approach, which can perform multiple aggregates <em>at the same time</em> on a stream of data, without buffering...</p> <p>An example is below...</p> <p><strong>why is this useful?</strong></p> <p>Because it allows you to write multiple queries on a data source using standard LINQ syntax, but only read it once.</p> <p><strong>Example</strong></p> <pre><code>using System; using System.Collections.Generic; using System.IO; using System.Linq; using MiscUtil.Linq; using MiscUtil.Linq.Extensions; static class Program { static void Main() { // prepare a query that is capable of parsing // the input file into the expected format string path = "foo.txt"; var qry = from line in ReadLines(path) let arr = line.Split(',') select new { Name = arr[0].Trim(), Male = arr[1].Trim() == "male", Birth = int.Parse(arr[2].Trim()), M1 = int.Parse(arr[3].Trim()) // etc }; // get a "data producer" to start the query process var producer = CreateProducer(qry); // prepare the overall average var avg = producer.Average(row =&gt; row.M1); // prepare the gender averages var avgMale = producer.Where(row =&gt; row.Male) .Average(row =&gt; row.M1); var avgFemale = producer.Where(row =&gt; !row.Male) .Average(row =&gt; row.M1); // run the query; until now *nothing has happened* - we haven't // even opened the file producer.ProduceAndEnd(qry); // show the results Console.WriteLine(avg.Value); Console.WriteLine(avgMale.Value); Console.WriteLine(avgFemale.Value); } // helper method to get a DataProducer&lt;T&gt; from an IEnumerable&lt;T&gt;, for // use with the anonymous type static DataProducer&lt;T&gt; CreateProducer&lt;T&gt;(IEnumerable&lt;T&gt; data) { return new DataProducer&lt;T&gt;(); } // this is just a lazy line-by-line file reader (iterator block) static IEnumerable&lt;string&gt; ReadLines(string path) { using (var reader = File.OpenText(path)) { string line; while ((line = reader.ReadLine()) != null) { yield return line; } } } } </code></pre>
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    1. POread text from file and apply some operations on it
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    1. USMarc Gravell
    1. USMarc Gravell
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    1. COthanx Marc but I'm not familier with using System.Linq;using MiscUtil.Linq;using MiscUtil.Linq.Extensions; but i will read about it and try to understand it thanx for your help I really I'm very thankful
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    2. COMiscUtil is a bespoke library by Jon Skeet, with some input from myself. The real question here is: how large is the data?
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    3. COits not large at all its max of 10 lines
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