How to fill Country, State and City dropdown list using linq to sql

In this article I am going to explain how to fill Country, State and City dropdown list using linq to sql

Description:
In the previous article I have explained Youtube autoplay and disable relatedvideos and Asp.net Embed Youtube video

I want to populate the Country, State and City dropdownlist.

Implementation:
I have created three tables Tb_Country, Tb_State and Tb_City.
How to fill Country, State and City dropdown list using linq to sql

HTML Markup of webform:

    <table>
    <tr>
    <td>Select Country:</td>
     <td>  <asp:DropDownList ID="ddlcountry" runat="server" AutoPostBack="true"
            onselectedindexchanged="ddlcountry_SelectedIndexChanged">
        </asp:DropDownList></td>
    </tr>
       <tr>
    <td></td>
     <td></td>
    </tr>
     <tr id="state" runat="server">
    <td>Select State:</td>
     <td><asp:DropDownList ID="ddlstate" runat="server" AutoPostBack="true"
            onselectedindexchanged="ddlstate_SelectedIndexChanged">
        </asp:DropDownList></td>
    </tr>
     <tr>
    <td></td>
     <td></td>
    </tr>
     <tr id="city" runat="server">
    <td>Select City:</td>
     <td> <asp:DropDownList ID="ddlcity" runat="server">
        </asp:DropDownList></td>
    </tr>
    </table>

Create object of DBML
C#:
BlogDataContext db = new BlogDataContext();

VB:
Private db As New BlogDataContext()

Bind the country dropdownlist
Write a method to bind the country dropdownlist and call it in page load event.
C#:
protected void Page_Load(object sender, EventArgs e)
    {
        city.Visible = false;
        state.Visible = false;
        if (!IsPostBack)
        {
            BindCountry();
        }
    } 
    public void BindCountry()
    {
        try
        {
            var country = from co in db.Tb_Countries
                          select co;
            ddlcountry.DataSource = country;
            ddlcountry.DataValueField = "Id";
            ddlcountry.DataTextField = "CountryName";
            ddlcountry.DataBind();
            ddlcountry.Items.Insert(0, new ListItem("--Select--", "0"));
        }
        catch (Exception ex)
        { }
    }

VB:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        city.Visible = False
        state.Visible = False
        If Not IsPostBack Then
            BindCountry()
        End If
    End Sub
    Public Sub BindCountry()
        Try
            Dim country = From co In db.Tb_Countries
                          Select co
            ddlcountry.DataSource = country
            ddlcountry.DataValueField = "Id"
            ddlcountry.DataTextField = "CountryName"
            ddlcountry.DataBind()
            ddlcountry.Items.Insert(0, New ListItem("--Select--", "0"))
        Catch ex As Exception
        End Try
    End Sub

Populate the state dropdownlist
On SelectIndexchanged event of country dropdown write the below given code
C#:
protected void ddlcountry_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            var state = from st in db.Tb_States
                        where st.CountryId_Fk == ddlcountry.SelectedIndex
                        select st;
            ddlstate.DataSource = state;
            ddlstate.DataValueField = "Id";
            ddlstate.DataTextField = "StateName";
            ddlstate.DataBind();
            ddlstate.Items.Insert(0, new ListItem("--Select--", "0"));           
        }
          
        catch (Exception ex)
        { }
        finally
        {
              state.Visible = true;
        }
    }

VB:
Protected Sub ddlcountry_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlcountry.SelectedIndexChanged
        Try
            Dim state = From st In db.Tb_States Where st.CountryId_Fk = ddlcountry.SelectedIndex
                        Select st
            ddlstate.DataSource = state
            ddlstate.DataValueField = "Id"
            ddlstate.DataTextField = "StateName"
            ddlstate.DataBind()
            ddlstate.Items.Insert(0, New ListItem("--Select--", "0"))

        Catch ex As Exception
        Finally
            state.Visible = True
        End Try
    End Sub

Populate the city dropdownlist
To SelectIndexchanged event of State dropdown write the below given code
C#:
protected void ddlstate_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            var city = from ct in db.Tb_Cities
                        where ct.StateId_Fk == Convert.ToInt32(ddlstate.SelectedValue)
                        select ct;
            ddlcity.DataSource = city;
            ddlcity.DataValueField = "Id";
            ddlcity.DataTextField = "CityName";
            ddlcity.DataBind();
            ddlcity.Items.Insert(0, new ListItem("--Select--", "0"));          
        } 
        catch (Exception ex)
        { }
        finally
        {
            state.Visible = true;
            city.Visible = true;
        }
    }

VB:
Protected Sub ddlstate_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlstate.SelectedIndexChanged
        Try
            Dim city = From ct In db.Tb_Cities Where ct.StateId_Fk = Convert.ToInt32(ddlstate.SelectedValue)
                       Select ct
            ddlcity.DataSource = city
            ddlcity.DataValueField = "Id"
            ddlcity.DataTextField = "CityName"
            ddlcity.DataBind()
            ddlcity.Items.Insert(0, New ListItem("--Select--", "0"))
        Catch ex As Exception
        Finally
            state.Visible = True
            city.Visible = True
        End Try
    End Sub

Build the project and run, test it.
 Result:
How to fill Country, State and City dropdown list using linq to sql

  In this article we have learn to how to populate the cascading dropdownlist using linq to sqlI hope you enjoyed this article.

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