CSharp - Use CopyToDataTable Operator When Primary Keys Are Established

Description

Use CopyToDataTable Operator When Primary Keys Are Established

Demo

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Data;

class Program//from w  w w . j a  va  2s.  c  o m
{
    static void Main(string[] args)
    {
        Student[] students = {
          new Student { Id = 1, Name = "Joe Ruby" },
          new Student { Id = 7, Name = "Apache Python" },
          new Student { Id = 13, Name = "Scala CSS" },
          new Student { Id = 72, Name = "Django SQL" }
        };

        DataTable dt1 = GetDataTable(students);
        DataTable newTable = dt1.AsEnumerable().CopyToDataTable();
        newTable.PrimaryKey = new DataColumn[] { newTable.Columns[0] };

        Console.WriteLine("Before upserting DataTable:");
        foreach (DataRow dataRow in newTable.AsEnumerable())
        {
            Console.WriteLine("Student Id = {0} : original {1} : current {2}",
              dataRow.Field<int>("Id"),
              dataRow.Field<string>("Name", DataRowVersion.Original),
              dataRow.Field<string>("Name", DataRowVersion.Current));
        }

        (from s in dt1.AsEnumerable()
         where s.Field<string>("Name") == "Apache Python"
         select s).Single<DataRow>().SetField("Name", "C++");

        dt1.AsEnumerable().CopyToDataTable(newTable, LoadOption.Upsert);

        Console.WriteLine("{0}After upserting DataTable:", System.Environment.NewLine);
        foreach (DataRow dataRow in newTable.AsEnumerable())
        {
            Console.WriteLine("Student Id = {0} : original {1} : current {2}",
              dataRow.Field<int>("Id"),
              dataRow.HasVersion(DataRowVersion.Original) ?
                dataRow.Field<string>("Name", DataRowVersion.Original) : "-does not exist-",
              dataRow.Field<string>("Name", DataRowVersion.Current));
        }

    }
    static DataTable GetDataTable(Student[] students)
    {
        DataTable table = new DataTable();

        table.Columns.Add("Id", typeof(Int32));
        table.Columns.Add("Name", typeof(string));

        foreach (Student student in students)
        {
            table.Rows.Add(student.Id, student.Name);
        }

        return (table);
    }
    static void OutputDataTableHeader(DataTable dt, int columnWidth)
    {
        string format = string.Format("{0}0,-{1}{2}", "{", columnWidth, "}");

        //  Display the column headings.
        foreach (DataColumn column in dt.Columns)
        {
            Console.Write(format, column.ColumnName);
        }
        Console.WriteLine();
        foreach (DataColumn column in dt.Columns)
        {
            for (int i = 0; i < columnWidth; i++)
            {
                Console.Write("=");
            }
        }
        Console.WriteLine();
    }

}


class Student
{
    public int Id;
    public string Name;
}

Result

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