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First, I am new to ASP.NET
In order to reuse my dropdown list across different forms on different pages, I was advised that to use User Control to accomplish this. So I did some reading about user control and attempted to play around with it, but couldn't get it work since I am new to ASP.NET. Get this error:
Cannot access a non-static member of outer type 'ASP.Vendor' via nested type 'ASP.Vendor._Default'
1) I create a Controls\Vendor.ascx file
<% @ Control Language="C#" ClassName="Vendor" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Web.UI" %>
<%@ Import Namespace="System.Web.UI.WebControls" %>
<%@ Import Namespace="System.Configuration" %>
<%@ Import Namespace="System.Linq" %>
<%@ Import Namespace="System.Collections.Generic" %>
<script runat="server">
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
FillVendor();
}
}
private void FillVendor()
{
string strConn = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
System.Data.SqlClient.SqlConnection conn = new System.Data.SqlClient.SqlConnection(strConn);
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT VendorID, VendorName FROM Vendor";
DataSet objDs = new DataSet();
SqlDataAdapter dAdapter = new SqlDataAdapter();
dAdapter.SelectCommand = cmd;;
conn.Open();
dAdapter.Fill(objDs);
conn.Close();
if (objDs.Tables[0].Rows.Count > 0)
{
VendorList.DataSource = objDs.Tables[0];
VendorList.DataTextField = "VendorName";
VendorList.DataValueField = "VendorID";
VendorList.DataBind();
VendorList.Items.Insert(0,"-- Select --");
} else {
lblMsg.Text = "No Vendor Found";
}
}
}
</script>
<asp:DropDownList ID="VendorList" runat="server" AutoPostBack="True" >
</asp:DropDownList>
2) I create a Tes2.aspx page with this code to see if I can pull that Vendor dropdown list, but no luck.
<%@ Page Language="C#" %>
<%@ Register TagPrefix="uc" TagName="Vendor"
Src="Controls\Vendor.ascx" %>
<html>
<body>
Testing
<form runat="server">
<uc:Vendor id="VendorList"
runat="server"
/>
</form>
</body>
Obviously, I am new and must doing thing wrong. Can someone please help me or give me an example of a dropdown list in user control and how to include it in a form? Thanks!
816
The first problem I see is that you are inheriting from Page inside your UserControl:
public partial class _Default : System.Web.UI.Page
Inherit from UserControl instead.
// notice that I also renamed the class to match the control name
public partial class Vendor : System.Web.UI.UserControl
As @x0n pointed out, your user control code can be placed in a codebehind file (automatically created when you create a user control inside Visual Studio). User controls typically consist of a markup portion (.ascx), a codebehind (.ascx.cs), and a designer file (.ascx.designer.cs). HTML markup goes into the ASCX file, and binding code goes into the codebehind.
I'd suggest saving your code, deleting your current user control, and re-adding it through Visual Studio.
Sample Project Structure
Markup (ASCX) File
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="VendorListControl.ascx.cs" Inherits="MyNamespace.VendorListControl" %>
<asp:DropDownList runat="server" ID="ddlVendorList" />
<asp:Label runat="server" ID="lblMessage" />
Codebehind
using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
namespace MyNamespace
{
public partial class VendorListControl : System.Web.UI.UserControl
{
protected void Page_Load( object sender, EventArgs e ) {
if( !IsPostBack ) {
FillVendors();
}
}
private void FillVendors() {
string strConn = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
System.Data.SqlClient.SqlConnection conn = new System.Data.SqlClient.SqlConnection( strConn );
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT VendorID, VendorName FROM Vendor";
DataSet objDs = new DataSet();
SqlDataAdapter dAdapter = new SqlDataAdapter();
dAdapter.SelectCommand = cmd; ;
conn.Open();
dAdapter.Fill( objDs );
conn.Close();
if( objDs.Tables[0].Rows.Count > 0 ) {
this.ddlVendorList.DataSource = objDs.Tables[0];
this.ddlVendorList.DataTextField = "VendorName";
this.ddlVendorList.DataValueField = "VendorID";
this.ddlVendorList.DataBind();
this.ddlVendorList.Items.Insert( 0, "-- Select --" );
}
else {
this.lblMessage.Text = "No Vendor Found";
}
}
}
}
Alternate Method - Remove Class Declaration
If you don't want to add a codebehind file for some reason, remove the class declaration altogether and just include the code inside it.
<script runat="server">
protected void Page_Load(object sender, EventArgs e){
if (!IsPostBack){
FillVendor();
}
}
// etc
</script>
As a side note, I would put the data access logic in a separate class for proper separation/reuse, but the structure you've outlined should work once you've corrected the aforementioned problems.
141
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