how to join two tables using linq query

Hi Kranthi,

Try in Google with 'Joins in LINQ'. See Google Results[^]

Some useful links here
Link 1[^]
Link 2[^]
LINQ Query Expressions [^]

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Configuration;
using System.Data.SqlClient;
using System.Reflection;


namespace LinqJOin
{
    public partial class Form1 : Form
    {
       // SqlConnection Con = new SqlConnection(ConfigurationManager.ConnectionStrings["MysqlCon"].ToString());
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
        //    SqlDataAdapter da1 = new SqlDataAdapter("select * from linqemp", Con);
        //DataTable dt1 = new DataTable();
        //da1.Fill(dt1);
        //dataGridView1.DataSource = dt1;



        //SqlDataAdapter da2 = new SqlDataAdapter("select * from emp1 ", Con);
        //DataTable dt2 = new DataTable();
        //da2.Fill(dt2);
        //dataGridView2.DataSource = dt2;
            DataTable dt = new DataTable();
            dt.Columns.Add("ID",typeof(string));
            dt.Columns.Add("Name", typeof(string));

            DataRow dr = dt.NewRow();
            dr["ID"] = "1";
            dr["Name"] = "Test1";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["ID"] = "2";
            dr["Name"] = "Test2";
            dt.Rows.Add(dr);

            DataTable dt1 = new DataTable();
            dt1.Columns.Add("ID", typeof(string));
            dt1.Columns.Add("Product", typeof(string));

            dr = dt1.NewRow();
            dr["ID"] = "1";
            dr["Product"] = "Test-Product";
            dt1.Rows.Add(dr);
            dataGridView1.DataSource = dt;
            dataGridView2.DataSource = dt1;



            var c = from p in dt.AsEnumerable()
                    join d in dt1.AsEnumerable() on p.Field<string>("ID") equals d.Field<string>("ID")
                    select new { ID = p.Field<string>("ID"), Name = p.Field<string>("Name"), Product = d.Field<string>("Product")};
            DataTable temp = new DataTable();
            temp = ConvertToDataTable(c);
            dataGridView3.DataSource = temp;
            comboBox1.Text = "ID";
            comboBox1.DataSource = temp;
          





           
        }
        #region LinqDatatable
        //For LinQ Application
        public DataTable ConvertToDataTable<T>(IEnumerable<T> varlist)
        {
            DataTable dtReturn = new DataTable();

            // column names   
            PropertyInfo[] oProps = null;

            if (varlist == null) return dtReturn;

            foreach (T rec in varlist)
            {
                // Use reflection to get property names, to create table, Only first time, others will follow   
                if (oProps == null)
                {
                    oProps = ((Type)rec.GetType()).GetProperties();
                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType;

                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }

                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }

                DataRow dr = dtReturn.NewRow();

                foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue
                    (rec, null);
                }

                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }
        #endregion
    }
}

Google[^] is your friend and 1 link[^] among them.

you can execute linq query and use the output data to bind in a datagridview to show data to your users:

dataGridView1.AutoGenerateColumns = false;
var BindInformation = from p in tbl_PersonInfo
join f in Financial on p.ID equals f.FinancialPersonID
select new {p.Name,p.Family,f.DebtValue,f.BestankarValue};

 dataGridView1.DataSource = BindInformation;

var getList = (from t1 in _objTTMSEntities.AssignedTaskInfoes join t2 in _objTTMSEntities.UserMasters
on t1.AssignedBy equals t2.UserID
where t1.AssignedToRoleType =="D"
select new { t1.ProjectName, t1.TaskID, t1.TaskName, t1.AssignedTo, t2.UserName,t1.StartDt, t1.EndDt }).ToList();



Joining three tables

var getList = (from t1 in _objTTMSEntities.AssignedTaskInfoes
                           join t2 in _objTTMSEntities.UserMasters on t1.AssignedBy equals t2.UserID
                           join t3 in _objTTMSEntities.UserMasters on t1.AssignedTo equals t3.UserID
                               where t1.AssignedToRoleType =="D"
                           select new { t1.ProjectName, t1.TaskID, t1.TaskName, t1.AssignedTo, t2.UserName,t1.StartDt, t1.EndDt }).ToList();

Note:select the columns from t3 table as required.