C# – Distinct records in DataTable

asp.netcdatasetdatatable

I want to get distinct records based on some fields. I'm using the following method:

string[] TobeDistinct = { "PKID" };
DataTable dtDistinct = GetDistinctRecords(ds.Tables[0], TobeDistinct);
DataSet ds2 = new System.Data.DataSet();
ds2.Tables.Add(dtDistinct);

public static DataTable GetDistinctRecords(DataTable dt, string[] Columns)
{
    DataTable dtUniqRecords = new DataTable();
    dtUniqRecords = dt.DefaultView.ToTable(true, Columns);
    return dtUniqRecords;
}

This gives me the distinct records, but only two records come. Only two distinct PKID will come. For example, I have multiple records with PKID 10,12,14,16, but the result is 2 rows with PKID 10 and 12. More two rows are not there, but should be there. What do I need to do?

I follow this article: http://www.codeproject.com/Tips/153008/Select-DISTINCT-records-based-on-specified-fields

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Best Answer

You can use like follows

DataView view = new DataView(table);
DataTable distinctValues = view.ToTable(true, "Column1", "Column2" ...);

More detail
How to select distinct rows in a datatable and store into an array

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C# – LINQ query on a DataTable

You can't query against the DataTable's Rows collection, since DataRowCollection doesn't implement IEnumerable<T>. You need to use the AsEnumerable() extension for DataTable. Like so:

var results = from myRow in myDataTable.AsEnumerable()
where myRow.Field<int>("RowNo") == 1
select myRow;

And as @Keith says, you'll need to add a reference to System.Data.DataSetExtensions

AsEnumerable() returns IEnumerable<DataRow>. If you need to convert IEnumerable<DataRow> to a DataTable, use the CopyToDataTable() extension.

Below is query with Lambda Expression,

var result = myDataTable
    .AsEnumerable()
    .Where(myRow => myRow.Field<int>("RowNo") == 1);

C# – LINQ’s Distinct() on a particular property

What if I want to obtain a distinct list based on one or more properties?

Simple! You want to group them and pick a winner out of the group.

List<Person> distinctPeople = allPeople
  .GroupBy(p => p.PersonId)
  .Select(g => g.First())
  .ToList();

If you want to define groups on multiple properties, here's how:

List<Person> distinctPeople = allPeople
  .GroupBy(p => new {p.PersonId, p.FavoriteColor} )
  .Select(g => g.First())
  .ToList();

Note: Certain query providers are unable to resolve that each group must have at least one element, and that First is the appropriate method to call in that situation. If you find yourself working with such a query provider, FirstOrDefault may help get your query through the query provider.

Note2: Consider this answer for an EF Core (prior to EF Core 6) compatible approach. https://stackoverflow.com/a/66529949/8155

Best Answer

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C# – LINQ query on a DataTable

C# – LINQ’s Distinct() on a particular property

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