CODEWITHSUNDEEP
c#-4.0parallel-processing
SchwartzE
SchwartzE

Reputation: 2628

Parallel ForEach on DataTable

I would like to use the new Parallel.ForEach function to loop through a datatable and perform actions on each row. I am trying to convert the code below:

        foreach(DataRow drow in dt.Rows)
        {
           ...
           Do Stuff
           ...
        }

To this code:

        System.Threading.Tasks.Parallel.ForEach(dt.Rows, drow =>
                {
                    ...
                    Do Stuff
                    ...
                });

When I run the new code I get the error:

The type arguments for method 'System.Threading.Tasks.Parallel.ForEach(System.Collections.Generic.IEnumerable, System.Action)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

What is the correct syntax for this?

Upvotes: 60

Views: 73152

Answers (5)

Indi_Rain
Indi_Rain

Reputation: 187

This way we can use Parallel.ForEach for Data table.

DataTable dtTest = new DataTable();
            dtTest.Columns.Add("ID",typeof(int));
            dtTest.Columns.Add("Name", typeof(string));
            dtTest.Columns.Add("Salary", typeof(int));

            DataRow dr = dtTest.NewRow();
            dr["ID"] = 1;
            dr["Name"] = "Rom";
            dr["Salary"] = "2000";
            dtTest.Rows.Add(dr);

            dr = dtTest.NewRow();
            dr["ID"] = 2;
            dr["Name"] = "David";
            dr["Salary"] = "5000";
            dtTest.Rows.Add(dr);

            dr = dtTest.NewRow();
            dr["ID"] = 3;
            dr["Name"] = "Samy";
            dr["Salary"] = "1200";
            dtTest.Rows.Add(dr);

            Parallel.ForEach(dtTest.AsEnumerable(), drow =>
            {
                MessageBox.Show("ID " + drow.Field<int>("ID") + " " + drow.Field<string>("Name") + " " + drow.Field<int>("Salary"));
            });

Upvotes: 1

irfandar
irfandar

Reputation: 1810

I had to modify Jon Skeet's answer to make it work.

Parallel.ForEach(dt.AsEnumerable<DataRowType>(), drow => {
     drow.SomeCol = "";
});

Upvotes: 0

Kevin .NET
Kevin .NET

Reputation: 473

This is better than the accepted answer because this does not need to reference System.Data.DataSetExtensions:

 Parallel.ForEach(dt.Rows.Cast<DataRow>(), dr =>

To use ForEach with a non-generic collection, you can use the Cast extension method to convert the collection to a generic collection, as shown in this example.

Upvotes: 19

JaredReisinger
JaredReisinger

Reputation: 7183

Parallel.ForEach() expects the first argument to be an IEnumerable<> type. DataTable.Rows is not, but you can turn it into one with the AsEnumerable() extension method. Try:

... Parallel.ForEach(dt.AsEnumerable(), drow => ...

Upvotes: 8

Jon Skeet
Jon Skeet

Reputation: 1502825

DataTable.Rows returns a DataRowCollection which only implements IEnumerable, not IEnumerable<DataRow>. Use the AsEnumerable() extension method on DataTable (from DataTableExtensions) instead:

Parallel.ForEach(dt.AsEnumerable(), drow =>
{
    ...
    Do Stuff
    ...
});

Upvotes: 127

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