Set default values for new DataRows added to an ADO.NET DataTable

You use the DefaultValue property of the DataColumn object.

    '
    ' Set default values.
    '
    With myDataSet.Tables("Orders")
        .Columns("Order_Date").DefaultValue = Today
        .Columns("Quantity").DefaultValue = 1
        . . .
    End With

    '
    ' Add the new row.
    '
    Dim aNewRow As DataRow = myDataSet.Tables("Orders").NewRow
    myDataSet.Tables("Orders").Rows.Add(aNewRow)

You can also specify the values each time you add a row:

    '
    ' Create a new row, set its values and add it.
    '
    Dim aNewRow As DataRow = myDataSet.Tables("Orders").NewRow
    
    With myDataSet.Tables("Orders")
        .Columns("Order_Date") = Today
        .Columns("Quantity") = 1
        . . .
        .Rows.Add(aNewRow)
    End With