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Accepted
J. Rodríguez
Asked: 2020-01-04 07:21:16 +0800 CST 2020-01-04 07:21:16 +0800 CST

How to compare 2 Dataset in C#?

  • 772

Both datasets have the same field structure, I need to pass to Dataset 2 the data Dataset 1that is NOT found in the Dataset 2.

  • The two columns to compare by are: DiaandFecha

Assuming the following data:

Data set 1:

enter image description here

Data set 2:

enter image description here

As can be seen, dataset 1 contains the day Thu. on date 01/04/2018 it is not found in dataset 2, therefore I need to pass only that value to the Dataset 2.

Dataset 2 may contain duplicate data (as you can see it contains twice the day Lun. 01/01/2018), BUT only the data that it already contained, previously loaded.

Both datasets contain 7 rows, but the end result should be that dataset 2 contains 8 rows after adding Thursday.

I did it in the following way, it is inserting the Juevesbut at the same time it is duplicating all the other data:

for (int indice = 0; indice < dataset1.Tables[0].Rows.Count; indice++)
{
     DateTime fecha_ds1 = Convert.ToDateTime(dataset1.Tables[0].Rows[indice]["Fecha"].ToString());
     string fecha1 = fecha_ds1.ToString("yyyy/MM/dd");
     string dia1 = dataset1.Tables[0].Rows[indice]["dia"].ToString();

     for (int indice2 = 0; indice2 < dataset2.Tables[0].Rows.Count; indice2++)
     {
         DateTime fecha_ds2 = Convert.ToDateTime(dataset2.Tables[0].Rows[indice2]["Fecha"].ToString());
         string fecha2 = fecha_ds2.ToString("yyyy/MM/dd");
         string dia2 = dataset1.Tables[0].Rows[indic2]["dia"].ToString();

         if (!fecha1.Equals(fecha2) && !dia1.Equals(dia2))
         {
             //Insertar la fila en Dataset 2 
             break; //y romper el ciclo para volver a tomar
                   //el siguiente valor del primer ciclo.
          }
      }
 }

So, how can I have a method that only returns the rows that are not in dataset2, and then inserts them?

Note: It may be to return a new dataset/datatable with those missing data.

EDITED:

Using : Visual Studio 2010 and Netframework 4

c#

2 Answers

  1. Best Answer

    You can use the LINQ function Exceptto get those DataRowfrom the first dataset that don't exist in the second.

    The only thing is that you must define a class that implements the interface IEqualityComparer<T>that passes Exceptthe logic that it must use to compare the data rows.

    You can define a class like the following (it can be a nested class for convenience if you wish):

    class DataRowEqualityComparer : IEqualityComparer<DataRow>
{
    public bool Equals(DataRow x, DataRow y)
    {
        return ((DateTime)x["Fecha"]).Date == ((DateTime)y["Fecha"]).Date;
    }

    public int GetHashCode(DataRow obj)
    {
        return ((DateTime)obj["Fecha"]).Date.GetHashCode();
    }
}

    Note that I simplify the date comparison logic, compared to what you already have, in the following 2 ways:

    • I ignore the field dia, because from what I can see, if the date matches, then the day will match as well, so it seems redundant to me to check this additional field.
    • Since you say in the comments that the type of the value Fechais already a DateTime, but that you want to compare this date without taking into account the portion that includes the time, the easiest way to do this is to use the function Dateof the class DateTime, which in the form directly gives you the date without the time.

    Now, with this class defined, you can get the desired result with the following LINQ expression:

    List<DataRow> dataRows =
    dataset1.Tables[0].Rows
        .Cast<DataRow>()
        .Except(dataset2.Tables[0].Rows.Cast<DataRow>(), new DataRowEqualityComparer())
        .ToList();

    Edition

    If you add the reference to System.Data.DataSetExtensions, as Sergio suggests, then the code can be a bit "cleaner":

    class DataRowEqualityComparer : IEqualityComparer<DataRow>
{
    public bool Equals(DataRow x, DataRow y)
    {
        return x.Field<DateTime>("Fecha").Date == y.Field<DateTime>("Fecha").Date;
    }

    public int GetHashCode(DataRow obj)
    {
        return obj.Field<DateTime>("Fecha").Date.GetHashCode();
    }
}

    LINQ:

    List<DataRow> dataRows =
    dataset1.Tables[0].AsEnumerable()
        .Except(dataset2.Tables[0].AsEnumerable(), new DataRowEqualityComparer())
        .ToList();

    Edition 2

    If you want to take the list of DataRowand add them to your second dataset, assuming both datasets have an identical structure, you can do it simply like this:

    foreach(var dataRow in dataRows)
{
    dataset2.Tables[0].Rows.Add(dataRow.ItemArray);
}
    • 2

  2. You need to add the reference to System.Data.DataSetExtensions

    then you treat it with linq to dataset

            var table0 = data.Tables[0].AsEnumerable();
        var table1 = data.Tables[1].AsEnumerable();

        var combined = table1.Union(table0);
    • 1