Merge (Join) two DataTables and insert into third using C# and VB.Net in ASP.Net

Hi PriyaKann,

Refer below sample code.

HTML

<asp:GridView runat="server" ID="gvEmployees"></asp:GridView>

Namespaces

C#

using System.Data;
using System.Linq;

VB.Net

Imports System.Data
Imports System.Linq

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    DataTable dt1 = new DataTable();
    dt1.Columns.AddRange(new DataColumn[] {
    new DataColumn("UserId"),
    new DataColumn("Name"),
    new DataColumn("Age"),
    new DataColumn("Salary") });
    dt1.Rows.Add("1", "Arun", 25);
    dt1.Rows.Add("2", "Bala", 30);
    dt1.Rows.Add("3", "Chandru", 35);
    dt1.Rows.Add("4", "Dinesh", 32);
    dt1.Rows.Add("5", "Ester", 27);
    dt1.PrimaryKey = new DataColumn[] { dt1.Columns["UserId"] };

    DataTable dt2 = new DataTable();
    dt2.Columns.AddRange(new DataColumn[] {
    new DataColumn("UserId"),
    new DataColumn("Name"),
    new DataColumn("Age"),
    new DataColumn("Designation") });
    dt2.Rows.Add("2", "Bala", 30, "Er");
    dt2.Rows.Add("3", "Chandru", 35, "Se.En");
    dt2.Rows.Add("6", "Farooq", 27, "Team Lead");
    dt2.Rows.Add("7", "Gokul", 35, "Engineer");
    dt2.Rows.Add("8", "Helen", 19, "Site Engineer");
    dt2.PrimaryKey = new DataColumn[] { dt2.Columns["UserId"] };

    dt1.Merge(dt2, false, MissingSchemaAction.Add);

    DataTable dt3 = new DataTable();
    dt3.Columns.AddRange(new DataColumn[] {
    new DataColumn("UserId"),
    new DataColumn("Name"),
    new DataColumn("Age") });

    var result = (from t1 in dt1.AsEnumerable()
                    select new
                    {
                        UserId = t1["UserId"].ToString(),
                        UserName = t1["Name"].ToString(),
                        Age = t1["Age"].ToString()
                    }).ToList();
    foreach (var item in result)
    {
        dt3.Rows.Add(item.UserId, item.UserName, item.Age);
    }

    gvEmployees.DataSource = dt3;
    gvEmployees.DataBind();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim dt1 As DataTable = New DataTable()
    dt1.Columns.AddRange(New DataColumn() {
                            New DataColumn("UserId"),
                            New DataColumn("Name"),
                            New DataColumn("Age"),
                            New DataColumn("Salary")})
    dt1.Rows.Add("1", "Arun", 25)
    dt1.Rows.Add("2", "Bala", 30)
    dt1.Rows.Add("3", "Chandru", 35)
    dt1.Rows.Add("4", "Dinesh", 32)
    dt1.Rows.Add("5", "Ester", 27)
    dt1.PrimaryKey = New DataColumn() {dt1.Columns("UserId")}

    Dim dt2 As DataTable = New DataTable()
    dt2.Columns.AddRange(New DataColumn() {
        New DataColumn("UserId"),
        New DataColumn("Name"),
        New DataColumn("Age"),
        New DataColumn("Designation")})
    dt2.Rows.Add("2", "Bala", 30, "Er")
    dt2.Rows.Add("3", "Chandru", 35, "Se.En")
    dt2.Rows.Add("6", "Farooq", 27, "Team Lead")
    dt2.Rows.Add("7", "Gokul", 35, "Engineer")
    dt2.Rows.Add("8", "Helen", 19, "Site Engineer")
    dt2.PrimaryKey = New DataColumn() {dt2.Columns("UserId")}

    dt1.Merge(dt2, False, MissingSchemaAction.Add)

    Dim dt3 As DataTable = New DataTable()
    dt3.Columns.AddRange(New DataColumn() {
                            New DataColumn("UserId"), New DataColumn("Name"),
                            New DataColumn("Age")})
    Dim result = (From t1 In dt1.AsEnumerable()
                    Select New With {
                    .UserId = t1("UserId"),
                    .UserName = t1("Name"),
                    .Age = t1("Age")
                }).ToList()

    For Each item In result
        dt3.Rows.Add(item.UserId, item.UserName, item.Age)
    Next

    gvEmployees.DataSource = dt3
    gvEmployees.DataBind()
End Sub

Screenshot