Question

C# inheriting a Gridview

Asked by: A_x_e_l

Hi I need to build a gridview control with a fixed header and scrolling contents - I have most of the code written but I would like to create a web user control from this - I do not want to compile this into a DLL just keep and use it (with source code) in the project. This project is for a big multinational customer and they have a strict approval process for Third party tools, so I have to roll my own. I seem to have problems using the correct base class - see my code below. I have tried to remove the Compiler errors I got by adding a name space but I get conflicting error messages about Namespaces vs. TagName.

With the usage below I am getting Unrecognized tag prefix or device filter 'uc1'. If I leave out the namespace from the Register line I get Element Scrollgridview is not a known element.

I am not sure whether the CodeFileBaseClass points to the correct Control, should I point it to the gridview? in which  assembly is this?

The syntax for assemplies is very complicated and not easy to understand for a C# newbie (I have done C++ for a lot of years 10 years ago, we used to program Windows based on a simple windows API - Petzold...)

Scrollgridview.ascx
=============
<%@ Control Language="C#" AutoEventWireup="true"
 CodeFile="ScrollGridView.ascx.cs" Inherits="Genbase.ScrollGridView"
 CodeFileBaseClass="System.Web.UI.UserControl" 
%>
 
 
Scrollgridview.ascx.cs
=============
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Text; // for StringBuilder
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;  // GridView
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
 
 
namespace Genbase
{
 
 
    public partial class ScrollGridView : System.Web.UI.WebControls.GridView
    {
 
        protected override void OnPreRender(EventArgs e)
        {
           // .. added code for injecting JScript to make the header non scrollable ...
           // .. added code for injecting JScript to make the header non scrollable ...
           // .. added code for injecting JScript to make the header non scrollable ...
         }
        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            Attributes.Add("style", "table-layout:fixed;");
        }
        protected override void Render(HtmlTextWriter writer)
        {
            writer.Write("<div id=\"" + ClientID + "_HeaderDivider\"></div>");
            if (Rows.Count > 10)
                writer.Write("<div style=\"overflow-y: scroll; height: 152px\">");
 
            base.Render(writer);
 
            if (Rows.Count > 10)
                writer.Write("</div>");
 
            if (ShowFooter)
                writer.Write("<div id=\"" + ClientID + "_FooterDivider\"></div>");
 
        }
    }
}
 
 
Testpage.aspx
 
<%@ Register TagPrefix="uc1" TagName="ScrollGridView" Src="ScrollGridView.ascx" Namespace="Genbase"  %>
 
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
 
                 <uc1:ScrollGridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
     DataKeyNames="ACCOUNT_NUM,ID,ID1,ID2" DataSourceID="SqlDataSource1">
                     <Columns>
                         <asp:BoundField DataField="status_desc" HeaderText="status_desc" SortExpression="status_desc" />
                         <asp:BoundField DataField="Status_1_desc" HeaderText="Status_1_desc" SortExpression="Status_1_desc" />
                         <asp:BoundField DataField="status_2_desc" HeaderText="status_2_desc" SortExpression="status_2_desc" />
                     </Columns>
                 </uc1:ScrollGridView>
                 <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:CFISQLConnectionString %>"
                     SelectCommand="spOIStatusGet" SelectCommandType="StoredProcedure"></asp:SqlDataSource>
 
</asp:Content>

                                  
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Asked On
2009-10-03 at 17:57:25ID24783087
Tags

C# ASP.NET 2.0

Topic

Programming for ASP.NET

Participating Experts
1
Points
500
Comments
3

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Answers

 

by: A_x_e_lPosted on 2009-10-04 at 03:10:48ID: 25488714

I have downloaded Reflector to check the assembly which contains the GridView control, and have changed the code for CodeFileBaseClass of ScrollGridview.ascx (see below) but I am still getting unrecognized tag prefix. Do I need to mention the namespace in the tag line of the html code somehow?


<%@ Control Language="C#" AutoEventWireup="true"
 CodeFile="ScrollGridView.ascx.cs" Inherits="Genbase.ScrollGridView"
 CodeFileBaseClass="System.Web.UI.WebControls"
%>
                                              
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by: strickddPosted on 2009-10-05 at 07:03:06ID: 25495298

I believe if you want to inherit from a control like this, you cannot use a custom control. You have to create a Class file and use that. This will be compiled into a DLL, if you compile the site, but it will stay in the project under the App_Code folder. This is no different than the .ascx.cs file with the custom control anyway.

The code below is an example that I've done to inherit from gridview.

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI.WebControls;
 
namespace MyControls
{
	/// <summary>
	/// Summary description for GridViewMoreDetails
	/// </summary>
	public class GridViewMoreDetails : GridView
	{
		public int MaxCharacterDisplay
		{
			get { return Utilities.CommonFunctions.ConvertToInt(ViewState[this.ID + "MaxCharacterDisplay"], 100); }
			set { ViewState[this.ID + "MaxCharacterDisplay"] = value; }
		}
 
		public GridViewMoreDetails()
		{
			//
			// TODO: Add constructor logic here
			//
		}
 
		protected override void OnDataBound(EventArgs e)
		{
			Panel divElement;
			Label spanElement;
			int rowNum = 0, cellNum = 0;
 
			foreach (GridViewRow row in this.Rows)
			{
				foreach (TableCell cell in row.Cells)
				{
					if (cell.Text.Length > MaxCharacterDisplay)
					{
						divElement = new Panel();
						divElement.ID = this.ID + "div" + rowNum.ToString() + cellNum.ToString();
 
						spanElement = new Label();
						spanElement.ID = this.ID + "span" + rowNum.ToString() + cellNum.ToString();
						spanElement.Style.Add("display", "none");
 
						divElement.Controls.Add(Utilities.CommonFunctions.CreateLiteral(cell.Text.Substring(0, MaxCharacterDisplay)));
						divElement.Controls.Add(spanElement);
						cell.Controls.Add(divElement);
 
						spanElement.Controls.Add(Utilities.CommonFunctions.CreateLiteral(cell.Text.Substring(MaxCharacterDisplay)));
						spanElement.Controls.Add(Utilities.CommonFunctions.CreateLiteral(" <span onclick=\"document.getElementById('" + spanElement.ClientID + "').style.display = 'none'; document.getElementById('" + divElement.ClientID + "MoreLink').style.display = '';\" style=\"cursor: pointer; color:Red; text-decoration:underline;\">(less)</span>"));
						divElement.Controls.Add(Utilities.CommonFunctions.CreateLiteral(" <span id='" + divElement.ClientID + "MoreLink' onclick=\"divWidth = document.getElementById('" + divElement.ClientID + "').offsetWidth; document.getElementById('" + spanElement.ClientID + "').style.display = '';document.getElementById('" + divElement.ClientID + "').style.width = divWidth + 'px'; document.getElementById('" + divElement.ClientID + "MoreLink').style.display = 'none';\" style=\"cursor: pointer; color:Red; text-decoration:underline;\">(more)</span>"));
					}
 
					cellNum++;
				}
 
				cellNum = 0;
				rowNum++;
			}
 
			base.OnDataBound(e);
		}
	}
}

                                              
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by: A_x_e_lPosted on 2009-10-05 at 07:19:11ID: 25495447

Hi strickdd, I will accept your solution, I had ended up deleting the aspx file and moved the class file into the App_Code folder. As we do not want to mess around with DLLs on deployments, we will keep the source within the project like that.

This way I also go tird of having to inject lost of JScript into the client events (messy).

I am still having some issues with the column sort events, as they delete the tbody and thead sections that I have inserted during OnPreRender:

(see first code snippet OnPreRender)

Although the sort triggers some client side script it still runs onprerender, but then the tbody and thead sections are not inserted anymore - I had to put the same code into the OnRowCeated event:

(see second code snippet OnRowCreated)

Now I only need to figure out how best to add a rightmost column so that the scrollbar does not eat into the screen space of tbody :) the rest, as they say, is CSS.

 protected override void OnPreRender(EventArgs e)
        {
            if (this.Rows.Count > 0)
            {
                //This replaces <td> with <th> and adds the scope attribute
                ((GridView)this).UseAccessibleHeader = true;
 
                //This will add the <thead> and <tbody> elements
                ((GridView)this).HeaderRow.TableSection = TableRowSection.TableHeader;
            }
 
        protected override void OnRowCreated(GridViewRowEventArgs e)
        {
            if (this.Rows.Count ==1) // inject at first row
            {
                ((GridView)this).UseAccessibleHeader = true;
                //This will add the <thead> and <tbody> elements
                ((GridView)this).HeaderRow.TableSection = TableRowSection.TableHeader;
            }
            base.OnRowCreated(e);
        }

                                              
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