CSharp - Join with SingleOrDefault Operator

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Description

Join with SingleOrDefault Operator

Demo

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

class Program/*from w  w w.  j  a  v a  2  s. co 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" }
        };

                StudentClass[] classDesignations = {
          new StudentClass { Id = 1, Class = "Sophmore" },
          new StudentClass { Id = 7, Class = "Freshman" },
          new StudentClass { Id = 13, Class = "Graduate" },
          new StudentClass { Id = 72, Class = "Senior" }
        };

        DataTable dt1 = GetDataTable(students);
        IEnumerable<DataRow> seq1 = dt1.AsEnumerable();
        DataTable dt2 = GetDataTable2(classDesignations);
        IEnumerable<DataRow> seq2 = dt2.AsEnumerable();

        string anthonysClass = (from s in seq1
                                where s.Field<string>("Name") == "Apache Python"
                                from c in seq2
                                where c.Field<int>("Id") == s.Field<int>("Id")
                                select (string)c["Class"]).
                               SingleOrDefault<string>();

        Console.WriteLine("Apache's Class is: {0}",
          anthonysClass != null ? anthonysClass : "null");


    }
    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();
    }
    static DataTable GetDataTable2(StudentClass[] studentClasses)
    {
        DataTable table = new DataTable();

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

        foreach (StudentClass studentClass in studentClasses)
        {
            table.Rows.Add(studentClass.Id, studentClass.Class);
        }

        return (table);
    }

}

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

Result

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