method of populate dropdownlist inside gridview - asp.net

Question

If i want to populate a DropdownList in a GridView what will be the best way? use GridView 'OnRowDataBound' event and fetch query everytime to db or get all data first and put it on datatable and do further work from this datatable ?

Answer 1

As your question is unclear about your requirement, I assume that you want to bind dropdownlist inside the Gridview using OnRowDataBound event of gridview.
So here are the steps:-
Add a Gridview HTML in your aspx page with DropDownList in ItemTemplate of TemplateField.
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
<Columns>
<asp:BoundField HeaderText="Name" DataField="ContactName" />
<asp:TemplateField HeaderText = "Country">
<ItemTemplate>
<asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Country") %>' Visible = "false" />
<asp:DropDownList ID="ddlCountries" runat="server">
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Then you need to bind the gridview with records which will come from the database.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GridView1.DataSource = GetData("SELECT ContactName, Country FROM Customers");
GridView1.DataBind();
}
}
private DataSet GetData(string query)
{
string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
SqlCommand cmd = new SqlCommand(query);
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataSet ds = new DataSet())
{
sda.Fill(ds);
return ds;
}
}
}
}
Then the code for OnRowDataBound will follow like below :-
protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
//Find the DropDownList in the Row
DropDownList ddlCountries = (e.Row.FindControl("ddlCountries") as DropDownList);
ddlCountries.DataSource = GetData("SELECT DISTINCT Country FROM Customers");
ddlCountries.DataTextField = "Country";
ddlCountries.DataValueField = "Country";
ddlCountries.DataBind();
//Add Default Item in the DropDownList
ddlCountries.Items.Insert(0, new ListItem("Please select"));
//Select the Country of Customer in DropDownList
string country = (e.Row.FindControl("lblCountry") as Label).Text;
ddlCountries.Items.FindByValue(country).Selected = true;
}
}
See the Reference link for your reference
Also see the Working demo for your reference
Hope that helps.