Parallel Processing C# - Merge data to global Datatable

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I have location of various csv files in "strFilePath" array(almost 1000 files which have 1 million records in each file). It takes a lot of time to read from files and merge all the data to single datatable. So I decided to go forward with Parallel processing. The question is, how can I merge all the data from datatable "dt" to a global datatable "dtMerge"?

C#

DataTable dtMerge=new DataTable();
for(int i=0;i<strFilePath.Count;i++)
{
     Parallel.For(0, 3,m =>
          clsNewClass objCls=new clsNewClass();
          DataTable dt=objCls.ReadCSV(strFilePath[m+i]);
      });
      m+=3;
}

Posted 13-Sep-14 19:12pm

thesarath

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George Jonsson · Answer 1 · 2014-09-13T21:21:00

You can try this code snippet.

C#

object padlock = new object();
DataTable dtMerge = new DataTable();
ParallelLoopResult result = Parallel.For(0, strFilePath.Count, index =>
{
    Debug.WriteLine("Iteration {0} : {1}", index, strFilePath[index]);
    clsNewClass objCls = new clsNewClass();
    DataTable dt = objCls.ReadCSV(strFilePath[index]);
    lock (padlock) // Makes sure only one merge operation is done at a time
    {
        dtMerge.Merge(dt);
    }
});
Debug.WriteLine("Result: {0}", result.IsCompleted ? "Completed Normally" : String.Format("Completed to {0}", result.LowestBreakIteration));

You should probably also look into the way you read data from the CSV file.
When you have so many files with that many lines, small inefficiencies here and there in the code will add up to a lot of time losses.
Even a millisecond per file will add up to 1 second slower time.