Using a DropDownList inside a GridView
Dropdowns are one of the most used basic controls just like a textbox. This article explains how to have a DropDownList inside a GridView. Basically the dropdowns have the AutoPostBack property to have a PostBack while selecting items. This can happen in GridView also, and can be implemented like in this article easily. But the understanding of SelectedIndexChanged plays an important role in writing applications with DropDownLists having PostBack.
DropDownList in Markup
Dropdown can be added to the mark up with the help of template columns. I usally keep the dropdown in the EditItemTemplate. But for easy explaining and easy understandings, I am keeping it under ItemTemplate.
Bind the DropDownList
As the DropDownList is inside the ItemTemplate, We have to get that using e.Row.FindControl(). This will give the control, and we can get the Data Source using a SQL Client and assign to the DataSource. Then the DataTextField is the field name which has to be shown in the screen. The DataValueField is the field name which has to be considered as a value for the respective text.
Enable PostBack to get SelectedIndexChanged
As I said just before, the DropDownList often needs PostBack. Implementing the PostBack event is required for that to be handled. Few steps basically we need to do
1) Enable the AutoPostBack by AutoPostBack="true".
2) Add an attribute for SelectedIndexChanged event
3) Write the Event in the code behind without the handles in the sub(refer the sample code here)
Source Code
Mark Up (*.ASPX)
<%@ Page Language=
"VB" AutoEventWireup=
"false" CodeFile=
"Default.aspx.vb" Inherits=
"_Default" %>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns=
"http://www.w3.org/1999/xhtml">
<head id=
"Head1" runat=
"server">
<title>Untitled Page</title>
</head>
<body>
<form id=
"form1" runat=
"server">
<asp:GridView runat=
"server" AutoGenerateColumns=
"false" ID=
"GridView1">
<Columns>
<asp:BoundField DataField=
"ProductName" HeaderText=
"ProductName" SortExpression=
"ProductName" />
<asp:BoundField DataField=
"UnitPrice" HeaderText=
"UnitPrice" SortExpression=
"UnitPrice" />
<asp:TemplateField >
<ItemTemplate>
<asp:DropDownList runat=
"server" ID=
"ddlCustomers" AutoPostBack=
"true" OnSelectedIndexChanged=
"ddlCustomers_SelectedIndexChanged"></asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</form>
</body>
</html>
Code-Behind(*.VB)
Imports System.Data.SqlClient
Imports System.Data
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub form1_Load(
ByVal sender
As Object,
ByVal e
As System.EventArgs)
Handles form1.Load
If (Not IsPostBack)
Then LoadGrid()
End If End Sub Private Sub LoadGrid()
GridView1.DataSource = GetSampleData()
GridView1.DataBind()
End Sub Private ReadOnly Property ConnectionString()
As String Get
Return "Server=.\SQLEXPRESS;Database=NorthWind;Trusted_Connection=True" End Get
End Property Private ReadOnly Property Connection()
As SqlConnection
Get
Dim ConnectionToFetch
As New SqlConnection(ConnectionString)
ConnectionToFetch.Open()
Return ConnectionToFetch
End Get
End Property Private Function GetSampleData()
As DataView
Dim SelectQry =
"select * from Products" Dim SampleSource
As New DataSet
Dim SampleView
As DataView
Try Dim SampleDataAdapter
As New SqlDataAdapter(SelectQry, ConnectionString)
SampleDataAdapter.Fill(SampleSource)
SampleView = SampleSource.Tables(0).DefaultView
Catch ex
As Exception
Throw ex
End Try Return SampleView
End Function Private Function GetCustomersData()
As DataView
Dim SelectQry =
"select * from Customers" Dim SampleSource
As New DataSet
Dim SampleView
As DataView
Try Dim SampleDataAdapter
As New SqlDataAdapter(SelectQry, ConnectionString)
SampleDataAdapter.Fill(SampleSource)
SampleView = SampleSource.Tables(0).DefaultView
Catch ex
As Exception
Throw ex
End Try Return SampleView
End Function Protected Sub ddlCustomers_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
Dim ddlCustomers = DirectCast(sender, DropDownList)
Response.Write(ddlCustomers.SelectedValue)
End Sub
Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
If (e.Row.RowType = DataControlRowType.DataRow) Then
Dim ddlCustomers As DropDownList = DirectCast(e.Row.FindControl("ddlCustomers"), DropDownList)
ddlCustomers.DataSource = GetCustomersData()
ddlCustomers.DataTextField = "ContactName"
ddlCustomers.DataValueField = "ContactName"
ddlCustomers.DataBind()
End If
End Sub
End Class