Custom DropDown List Server Control

Hi posted a problem about dynamic tables but realize i was tackling a giant without learning how to punch first. I just realized my other more simpler controls are not able to save view state also. What i want is simple. I just want to have a custom dropdown list that inherits everything the dropdown list have. No customization yet whatsover. Tried to use the code but its not loading the items to the dropdownlist...please help

heres the code for both server control and webform. I checked the datatable it has items in it so its not a problem with the data source. Anyone knows whats wrong with it?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

namespace SFAHPOI
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:NpaxDropDown runat=server></{0}:NpaxDropDown>")]
    public class NpaxDropDown : DropDownList, IPostBackDataHandler
    {
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string Text
        {
            get
            {
                String s = this.Text;
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                this.Text = value;
                EnsureChildControls();
            }
        }
        [Bindable(true)]
        [Category("DataBind")]
        [DefaultValue("")]
        [Localizable(true)]
        public DataTable DataSource
        {
            get
            {
                DataTable s = (DataTable)ViewState["DataSource"];

                return ((s == null) ? new DataTable(): s);
            }

            set
            {
                ViewState["DataSource"] = value;
                EnsureChildControls();
            }
        }
        [Bindable(true)]
        [Category("DataBind")]
        [DefaultValue("")]
        [Localizable(true)]
        public string DataValueField
        {
            get
            {
                
                String s = (string)ViewState["DataValueField"];
                if (s == null)
                {
                    return String.Empty;
                }
                else
                {
                    return s;
                }
            }

            set
            {
                ViewState["DataValueField"]=value;
                EnsureChildControls();
            }
        }
        [Bindable(true)]
        [Category("DataBind")]
        [DefaultValue("")]
        [Localizable(true)]
        public string DataTextField
        {
            
            get
            {
                String s = (string)ViewState["DataTextField"];
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                
                ViewState["DataValueField"] = value;
                EnsureChildControls();
            }
        }
        
 
       protected override void  CreateChildControls()
        {
            this.DataTextField = DataTextField;
            this.DataValueField = DataValueField;
            this.DataSource = DataSource;
           
 	    base.CreateChildControls();
        }
               
     
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using SFAHPOI;
using System.Data;
using HpoiBL;
using DevExpress.XtraCharts.Web;

namespace HPOI_SFA
{
    public partial class WebForm4 : System.Web.UI.Page
    {
        string[] usernames= new string[5];
        int s;
        ScreenMasterBL SM;


        protected void Page_Load(object sender, EventArgs e)
        {
           

            if (!IsPostBack)
            {
                             
                NpaxDropDown1.DataSource = SM.GetScreens();
                NpaxDropDown1.DataValueField = "ScreenID";
                NpaxDropDown1.DataTextField = "ScreenName";
                NpaxDropDown1.DataBind();
                
                              
            }
            
           
            else
            {
                
            }
            
        }

       
      


      }
}

Re: Custom DropDown List Server Control

You need to inherit custom control class by "DataBoundControl" which is a data-bound control base class.

refer the links below.

http://msdn.microsoft.com/en-us/library/ms366539.aspx

Simple DataBoundControl implementation

http://msdn.microsoft.com/en-us/library/ms366540.aspx

Hope this helps.

Re: Custom DropDown List Server Control

avinash_bhudke

You need to inherit custom control class by "DataBoundControl" which is a data-bound control base class.

refer the links below.

http://msdn.microsoft.com/en-us/library/ms366539.aspx

Simple DataBoundControl implementation

http://msdn.microsoft.com/en-us/library/ms366540.aspx

Hope this helps.

Isnt the DropDownList already a data bound control? whats the point of inheriting the object if u cant use the properties that it already has?

Re: Custom DropDown List Server Control

Hello mba

YesDropdownlist itself has the property of DataSourceDataTextField as well as DataValue FieldSo no need for you to create these propertiesothersisesyou will hide them

So try this

[DefaultProperty("Text")]
    [ToolboxData("<{0}:NpaxDropDown runat=server></{0}:NpaxDropDown>")]
    public class NpaxDropDown : DropDownList, IPostBackDataHandler
    {
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public override string Text
        {
            get
            {
                String s = this.Text;
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                this.Text = value;
                EnsureChildControls();
            }
        }

        protected override void CreateChildControls()
        {
            this.DataTextField = DataTextField;
            this.DataValueField = DataValueField;
            this.DataSource = DataSource;

            base.CreateChildControls();

            ChildControlsCreated = true;
        }


    }

Re: Custom DropDown List Server Control

yes it works now..thank you very much. i dont know what happened the first time