How to cascading dropdownlist in gridview in asp.net?

Hi Mahendra,
 
Try this,
 

First you have to create 3 DropDown into your aspx page and set AutoPostBack="ture" and also it's OnCheckedChanged Event which will call code behind function.
 
First in Page load you have to bind Country DropDown and on Country DropDown OnCheckedChanged event you have to bind State DropDown and on State DropDown OnCheckedChanged event you have to bind City DropDown .
 
Like This,
 
On .Aspx Page :=
 

<asp:DropDownList ID="ddlCountry" runat="server" Width="100%" AutoPostBack="true"
                                                       CausesValidation="false" 
                                                       OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged" CssClass="divisionClass">
                                                   </asp:DropDownList>

 

<asp:DropDownList ID="ddlState" runat="server" AutoPostBack="true" Width="100%" OnSelectedIndexChanged="ddlState_SelectedIndexChanged"
                                                        CausesValidation="false"  CssClass="divisionClass">
                                                    </asp:DropDownList>

<asp:DropDownList ID="ddlCity" runat="server" AutoPostBack="true" Width="100%" OnSelectedIndexChanged="ddlCity_SelectedIndexChanged"
                                                        CausesValidation="false"  CssClass="divisionClass">
                                                    </asp:DropDownList>

 

On Code Behind Page that is .cs :=
 
In Page Load Write Below Function :
 

ddlCountry.DataSource = fn_getCountry()
            ddlCountry.DataTextField = "CountryName"
            ddlCountry.DataValueField = "CountryID"
            ddlCountry.DataBind()
            ddlCountry.Items.Insert(0, New ListItem("Select Country", ""))
            ddlState.Items.Insert(0, New ListItem("Select State", ""))
            ddlCity.Items.Insert(0, New ListItem("Select City", ""))
            ddlState.Enabled = False
            ddlCity.Enabled = False

 
then
 

protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
<pre lang="sql">ddlState.DataSource = fn_getStateByCountryID(countryID)
                ddlState.DataTextField = "StateName"
                ddlState.DataValueField = "StateID"
                ddlState.DataBind()
                ddlState.Items.Insert(0, New ListItem("Select State", ""))
                ddlCity.SelectedIndex = 0
                ddlState.Enabled = True
                ddlCity.Enabled = False

 

}  

protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
 
<pre lang="sql">ddlCity.DataSource = fn_getCityByStateID(stateID)
                ddlCity.DataTextField = "CityName"
                ddlCity.DataValueField = "CityID"
                ddlCity.DataBind()
                ddlCity.Items.Insert(0, New ListItem("Select City", ""))
                ddlCity.Enabled = True

 
}  

protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
{
 
}

 

Here,
fn_getCountry is a function which will Execute a query and Holding a list of Country.
fn_getStateByCountryID(countryID) is function which will hold a State list of Selected Country.
and
fn_getCityByStateID(stateID) is function which will hold a City list of Selected State.
 
All d Best,
 
I Hope this will help You.

Well there is a control named:
ASP.NET AJAX Cascading Drop Down Control you can implement it easily;
AJAX Cascading Drop Down Control[^]
AJAX Cascading Drop Down with Database[^]
A video tutorial[^]
A similar example that you may want to look[^]

Have a look at these:
Implementing Cascading DropDownList in ASP.NET GridView[^]
Ajax Cascading DropDownList With Database Example in GridView[^]
 
If needed, look here[^] for more.

check this solution http://www.4microsoftsolutions.com/post/CascadingDropDown-Control-in-ASPNET-AJAX.aspx[^]