Override Content Query Webpart to do on the run filteration.

Problem

In one of my recent project I had a challenge of filtering the data with localization.
The project contained 2 languages, English and Spanish. I was trying to find out the out of the box way to get this done, but no help was available.


Solution

1. Create a new empty project in Visual Studio 2010.
2. Add a webpart to the project. "Webpart" not "Visual Web Part".
3. Replace the Webpart class inherited and make it "Microsoft.SharePoint.Publishing.WebControls.ContentByQueryWebPart".
4. Please have a look at the code below. It will have on the fly list settings and field settings applied to the webpart.
5. Build your code and deploy it. It should work.

Source Code

#region System
using System;
using System.ComponentModel;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
#endregion

// Create the Toolbar
namespace ToolBar.ToolBar
{
    [ToolboxItemAttribute(false)]
    public class ToolBar : Microsoft.SharePoint.Publishing.WebControls.ContentByQueryWebPart
    {
        #region Properties

        /// <summary>
        /// Root Site Name
        /// </summary>
        private string SiteUrl { get { return SPContext.Current.Site.RootWeb.Url; } }

        /// <summary>
        /// List Name
        /// </summary>
        private string ListName { get { return "ToolBar"; } }

        /// <summary>
        /// List of Url
        /// </summary>
        private string ListUrl
        {
            get
            {
                return string.Format("{0}/Lists/{1}/AllItems.aspx", SiteUrl, ListName);
            }
        }

        #endregion

        #region Methods

        /// <summary>
        /// On Page Load
        /// </summary>
        /// <param name="e"></param>
        protected override void OnInit(EventArgs e)
        {
            //On Load
            base.OnLoad(e);

            //General Settings
            this.AllowConnect = true;
            this.ShowUntargetedItems = false;
            this.AllowEdit = true;
            
            //this.FrameType = "NONE"; // TODO
            this.ChromeType = PartChromeType.None;
            this.ExportMode = WebPartExportMode.All;
            this.GroupByDirection = SortDirection.Desc;
            this.SortByDirection = SortDirection.Desc;
            
            this.ConnectionID = System.Guid.Empty;
            this.ListId = System.Guid.Empty;

            this.ViewFlag = "0";
            this.GroupingText = "GP Web Parts";
            this.Title = " Tool Bar";
            this.ContentTypeName = "Item";
            this.ItemStyle = "ToolBar";
            this.ServerTemplate = "100";
            this.GroupStyle = "DefaultHeader";
            this.WebUrl = "~sitecollection";
            this.Description = "Displays a dynamic view of content from your site.";
            this.Xsl = "<xsl:stylesheet xmlns:x=\"http://www.w3.org/2001/XMLSchema\" version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" xmlns:cmswrt=\"http://schemas.microsoft.com/WebPart/v3/Publishing/runtime\" exclude-result-prefixes=\"xsl cmswrt x\" > <xsl:import href=\"/Style Library/XSL Style Sheets/Header.xsl\" /> <xsl:import href=\"/Style Library/XSL Style Sheets/ItemStyle.xsl\" /> <xsl:import href=\"/Style Library/XSL Style Sheets/ContentQueryMain.xsl\" /> </xsl:stylesheet>";
            this.SampleData = "<dsQueryResponse><Rows><Row Title=\"Item 1\" LinkUrl=\"http://Item1\" Group=\"Group Header\" __begincolumn=\"True\" __begingroup=\"True\" /><Row Title=\"Item 2\" LinkUrl=\"http://Item2\" __begincolumn=\"False\" __begingroup=\"False\" /><Row Title=\"Item 3\" LinkUrl=\"http://Item3\" __begincolumn=\"False\" __begingroup=\"False\" /></Rows></dsQueryResponse>";
            this.ParameterBindings = string.Empty;

            //Root Web
            using (SPWeb _web = SPContext.Current.Site.RootWeb)
            {
                //Assign the list to the CQWP
                SPList _listYCLToolBar = _web.GetListFromUrl(ListUrl);

                //Data mapping
                this.DataMappings = string.Format("Description:|LinkUrl:{2},TargetUrl,URL;|Title:{4},Title,Text;|NumComments:|PublishedDate:|PostCategory:|ImageUrlAltText:{0},Title,Text;|Author:|Language:{3},Language,Lookup;|ImageUrl:{1},Icon,URL;|Body:|"
                    , _listYCLToolBar.Fields["Title"].Id.ToString()
                    , "{" + _listYCLToolBar.Fields["Icon"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["TargetUrl"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["Language"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["Title"].Id.ToString() + "}"
                    );

                this.ListGuid = _listYCLToolBar.ID.ToString();

                this.DataMappingViewFields = string.Format("{0},URL;{1},URL;{2},Text;{3},Lookup;"
                    , "{" + _listYCLToolBar.Fields["TargetUrl"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["Icon"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["Title"].Id.ToString() + "}"
                    , "{" + _listYCLToolBar.Fields["Language"].Id.ToString() + "}"
                    );
                
                //Filter One
                this.FilterField1 = "Language";//Custom Field to get the variation work.
                this.FilterOperator1 = FilterFieldQueryOperator.Eq;
                this.FilterValue1 = System.Globalization.CultureInfo.CurrentCulture.IetfLanguageTag;
                this.FilterType1 = "Lookup";
                this.Filter1ChainingOperator = FilterChainingOperator.Or;

                this.Filter2ChainingOperator = FilterChainingOperator.Or;

                //Sorting
                this.SortByFieldType = "DateTime";
                this.SortBy = "Created";
            }            
        }

        /// <summary>
        /// Create Child Controls
        /// </summary>
        protected override void CreateChildControls()
        {
            base.CreateChildControls();
        }

        #endregion
    }
}

Please let me know if there is any issue with this code or you can also correct me if I am wrong.