Related Items webpart

Scenario:
I always wondered why this web part is missing. On the edit form / new form of any item, we always wanted to show things which are connected to a particular entity.

Solution:
Related Items webpart



Code:

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;

namespace SKN.SPWebparts
{
    [Guid("027a38e8-684a-4f0a-8dde-11c3abaad1cd")]
    public class RelatedItems : System.Web.UI.WebControls.WebParts.WebPart
    {
        private const string const_configuationListName = "Session Docs";
        private string m_configuationListName = const_configuationListName;

        // Configuration List Name property.  
        [Personalizable(PersonalizationScope.Shared)]
        [WebBrowsable(true)]
        [Category("Custom Properties")]
        [WebDisplayName("Configuration List Name")]
        [Description("Configuration List Name")]
        [DefaultValue(const_configuationListName)]
        public string ConfigurationListName
        {
            get
            {
                return m_configuationListName;
            }

            set
            {
                m_configuationListName = value;
            }
        }

        private const string const_configuationFieldName = "ProjectCode";
        private string m_configuationFieldName = const_configuationFieldName;

        // Configuration Field Name property.    
        [Personalizable(PersonalizationScope.Shared)]
        [WebBrowsable(true)]
        [Category("Custom Properties")]
        [WebDisplayName("Configuration Field Name")]
        [Description("Configuration Field Name")]
        [DefaultValue(const_configuationFieldName)]
        public string ConfigurationFieldName
        {
            get
            {
                return m_configuationFieldName;
            }

            set
            {
                m_configuationFieldName = value;
            }
        }


        private const string const_configuationAddNewItemLink = "";
        private string m_configuationAddNewItemLink = const_configuationAddNewItemLink;

        // Configuration Add new item link.
        [Personalizable(PersonalizationScope.Shared)]
        [WebBrowsable(true)]
        [Category("Custom Properties")]
        [WebDisplayName("Add new item link")]
        [Description("Set this property to show add new item link.Leave blank for newform.aspx")]
        [DefaultValue(const_configuationAddNewItemLink)]
        public string ConfigurationAddNewLink
        {
            get
            {
                return m_configuationAddNewItemLink;
            }

            set
            {
                m_configuationAddNewItemLink = value;
            }
        }

        private const string const_configuationAddNewItemText = "Add new item";
        private string m_configuationAddNewItemLinkText = const_configuationAddNewItemText;

        // Configuration Add new item link text.
        [Personalizable(PersonalizationScope.Shared)]
        [WebBrowsable(true)]
        [Category("Custom Properties")]
        [WebDisplayName("Add new item link text")]
        [Description("Set this property to set the text for the add new item link.")]
        [DefaultValue(const_configuationAddNewItemText)]
        public string ConfigurationAddNewLinkText
        {
            get
            {
                return m_configuationAddNewItemLinkText;
            }

            set
            {
                m_configuationAddNewItemLinkText = value;
            }
        }

        const string const_AddNewItemLinkHTML = @"<TABLE border=0 cellSpacing=0 cellPadding=0 width='100%'>
                    <TBODY>
                    <TR>
                    <TD class=ms-partline colSpan=2><IMG alt='' src='/_layouts/images/blank.gif' width=1 height=1></TD></TR>
                    <TR>
                    <TD style='PADDING-BOTTOM: 3px;PADDING-TOP: 5px;PADDING-LEFT: 5px' class=ms-addnew><IMG alt='' src='/_layouts/images/rect.gif'> <A id=idHomePageNewEvent class=ms-addnew onclick='javascript:NewItem('{0}', true);javascript:return false;' href='{0}' target=_self>{1}</A> </TD></TR>
                    <TR>
                    <TD><IMG alt='' src='/_layouts/images/blank.gif' width=1 height=5></TD>
                    </TR>
                    </TBODY>
                    </TABLE>";

        public RelatedItems ()
        {

        }

        protected override void CreateChildControls ()
        {
            base.CreateChildControls();
        }

        public override void RenderControl (HtmlTextWriter writer)
        {
            if (!string.IsNullOrEmpty(ConfigurationListName))
            {
                ListViewByQuery listviewByQueryWP = new ListViewByQuery();

                SPWeb currentweb = SPContext.Current.Web;
                SPListItem currentList = SPContext.Current.ListItem;

                SPList relatedList = currentweb.Lists[ConfigurationListName];
                SPQuery query = new SPQuery(relatedList.DefaultView);

                query.Query = string.Format("<where><contains><fieldref name='{0}'><value type='Text'>{1}</value></fieldref></contains></where>", ConfigurationFieldName, currentList.Title);

                listviewByQueryWP.List = relatedList;
                listviewByQueryWP.Query = query;
                EnsureChildControls();
                listviewByQueryWP.RenderControl(writer);
                RenderChildren(writer);

                if (relatedList.DoesUserHavePermissions(SPBasePermissions.EditListItems))
                {
                    if (string.IsNullOrEmpty(ConfigurationAddNewLink))
                    {
                        ConfigurationAddNewLink = SPContext.Current.Web.Url + "/" + relatedList.Forms[PAGETYPE.PAGE_NEWFORM].Url;
                    }
                    string queryParamValue = string.Format("?{0}={1}&Source={2}", ConfigurationFieldName, currentList.Title, HttpContext.Current.Server.UrlEncode(HttpContext.Current.Request.Url.AbsoluteUri));
                    writer.Write(string.Format(const_AddNewItemLinkHTML, ConfigurationAddNewLink + queryParamValue, ConfigurationAddNewLinkText));
                }
            }
        }
    }
}