How to use Join in LINQ Query

Introduction: In this post I have try to explain how we can use the Joins in LINQ.

Description:

In the last article i have explained How to insert data into database using LINQ, How to Bind, Edit, Update and Delete in Gridview Control in LINQ and Send Password Reset Link in Asp.net.
I have created two tables.

LINQ_TABLE

LINQ_STATE (ID is primary key)

ID	int
STATE	varchar(50)

Add a web form to application. Go to Solution Explorer, right click on website>Add new item> Web from.

Drag and drop a Gridview Data control from from Toolbox>Data.

<asp:GridView ID="grduser" runat="server" AutoGenerateColumns="False"

            AllowPaging="True" onpageindexchanging="grduser_PageIndexChanging"

            >

            <Columns>

                <asp:TemplateField HeaderText="Username">

                                      <ItemTemplate>

                        <asp:Label ID="lbluser" runat="server" Text='<%# Eval("USERNAME") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="First Name">

                    <ItemTemplate>

                        <asp:Label ID="lblfirst" runat="server" Text='<%# Eval("FIRST_NAME") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="Last Name">

                    <ItemTemplate>

                        <asp:Label ID="lbllast" runat="server" Text='<%# Eval("LAST_NAME") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="Date Of Birth">

                    <ItemTemplate>

                        <asp:Label ID="lblbirth" runat="server" Text='<%# Eval("DATE_BIRTH") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="Sex">

                    <ItemTemplate>

                        <asp:Label ID="lblsex" runat="server" Text='<%# Eval("SEX") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="Age">

                    <ItemTemplate>

                        <asp:Label ID="lblage" runat="server" Text='<%# Eval("AGE") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="Profile Image">

                    <ItemTemplate>

                        <asp:Image ID="Image1" runat="server" ImageUrl='<%# Eval("IMAGE") %>' Height="100px" Width="100px" />

                    </ItemTemplate>

                </asp:TemplateField>

                <asp:TemplateField HeaderText="State">

                <ItemTemplate>

                <asp:Label ID="lbldepartment" runat="server" Text='<%#Eval("STATE") %>'></asp:Label>

                </ItemTemplate>

                </asp:TemplateField>

            </Columns>

        </asp:GridView>

Now go to .aspx.cs page.

DataClassesDataContext db = new DataClassesDataContext();

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

            Bindgrid();

        }

    }

    private void Bindgrid()

    {

        //inner join

        var bind = from v in db.LINQ_TABLEs

                   join d in db.LINQ_STATEs on v.ID equals d.ID

                   select new

                   {

                       v.USERNAME,

                       v.FIRST_NAME,

                       v.LAST_NAME,

                       v.DATE_BIRTH,

                       v.SEX,

                       v.AGE,

                       v.IMAGE,

                       d.STATE

                   };

grduser.DataSource = bind;

        grduser.DataBind();

    }

    protected void grduser_PageIndexChanging(object sender, GridViewPageEventArgs e)

    {

        grduser.PageIndex = e.NewPageIndex;

        Bindgrid();

    }

In VB

Private db As New DataClassesDataContext()

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then

            Bindgrid()

        End If

    End Sub

    Private Sub Bindgrid()

        'inner join

        Dim bind = From v In db.LINQ_TABLEs Join d In db.LINQ_STATEs

                  On v.ID Equals d.ID

                   Select v.USERNAME, v.FIRST_NAME, v.LAST_NAME, v.DATE_BIRTH,

                   v.SEX, v.AGE, v.IMAGE, d.STATE

        grduser.DataSource = bind

        grduser.DataBind()

    End Sub

    Protected Sub grduser_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)

        grduser.PageIndex = e.NewPageIndex

        Bindgrid()

    End Sub

Now run the project and check the result.