Developing data source web parts

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="DataSourceControl.ascx.cs" Inherits="CMSGlobalFiles_DataSourceControl" %>
<%--Leave the markup of the first user control empty--%>

using System;

using System.Data;

using CMS.Controls;
using CMS.Membership;
using CMS.FormControls;

/// <summary>
/// User data source. Loads all users according to a specified Where condition.
/// </summary>
public partial class CMSGlobalFiles_DataSourceControl : CMSBaseDataSource
{
    /// <summary>
    /// Assigns a handler for the 'OnFilterChanged' event if there is a filter attached to the data source.
    /// You do not need to implement this method if you do not plan to use filters with the data source web part.
    /// </summary>
    protected override void OnInit(EventArgs e)
    {
        if (SourceFilterControl != null)
        {
            SourceFilterControl.OnFilterChanged += new ActionEventHandler(DataFilter_OnFilterChanged);
        }

        base.OnInit(e);
    }

    /// <summary>
    /// Handles the OnFilterChanged event.
    /// You do not need to implement this method if you do not plan to use filters with the data source web part.
    /// </summary>
    void DataFilter_OnFilterChanged()
    {
        // Clears the old data
        InvalidateLoadedData();

        // Raises the change event
        this.RaiseOnFilterChanged();
    }

    /// <summary>
    /// Loads the data of the data source.
    /// </summary>
    protected override object GetDataSourceFromDB()
    {
        // Initializes the data properties according to the filter settings
        if (SourceFilterControl != null)
        {
            SourceFilterControl.InitDataProperties(this);
        }

        // Loads the data. The WhereCondition and OrderBy properties are inherited from the parent class.
        DataSource = UserInfoProvider.GetFullUsers(WhereCondition, OrderBy);

        return DataSource;
    }
}

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="~/CMSGlobalFiles/DataSourceWebPart.ascx.cs" Inherits="CMSGlobalFiles_DataSourceWebPart" %>

<%@ Register Src="~/CMSGlobalFiles/DataSourceControl.ascx" TagPrefix="cms" TagName="DataSourceControl" %>

<cms:DataSourceControl ID="srcUsers" runat="server" />

using CMS.PortalControls;
using CMS.Helpers;

public partial class CMSGlobalFiles_DataSourceWebPart : CMSAbstractWebPart
{
    /// <summary>
    /// Gets or sets the value of the WhereCondition web part property.
    /// </summary>
    public string WhereCondition
    {
        get
        {
            return ValidationHelper.GetString(this.GetValue("WhereCondition"), "");
        }
        set
        {
            this.SetValue("WhereCondition", value);
            srcUsers.WhereCondition = value;
        }
    }

    /// <summary>
    /// Gets or sets the value of the OrderBy web part property.
    /// </summary>
    public string OrderBy
    {
        get
        {
            return ValidationHelper.GetString(this.GetValue("OrderBy"), "");
        }
        set
        {
            this.SetValue("OrderBy", value);
            srcUsers.OrderBy = value;
        }
    }

    /// <summary>
    /// Gets or sets the value of the FilterName web part property.
    /// </summary>
    public string FilterName
    {
        get
        {
            return ValidationHelper.GetString(this.GetValue("FilterName"), "");
        }
        set
        {
            this.SetValue("FilterName", value);
            srcUsers.SourceFilterName = value;
        }
    }

    /// <summary>
    /// Content loaded event handler.
    /// </summary>
    public override void OnContentLoaded()
    {
        base.OnContentLoaded();
        SetupControl();
    }

    /// <summary>
    /// Initializes the properties of the internal data source control.
    /// </summary>
    protected void SetupControl()
    {
        if (this.StopProcessing)
        {
            // Does nothing if the web part is disabled
        }
        else
        {
            this.srcUsers.WhereCondition = this.WhereCondition;
            this.srcUsers.OrderBy = this.OrderBy;

            // Sets the inner data source's name according to the web part's 'Web part control ID' property.
            // This allows listing web parts to connect to the inner control.
            // The identifier property is named 'FilterName' because data sources inherit the property from 
            // a base class shared with filter objects.
            this.srcUsers.FilterName = (string)this.GetValue("WebPartControlID");

            // Connects the attached filter, as specified by the 'Filter name' property of the web part
            this.srcUsers.SourceFilterName = this.FilterName;
        }
    }
}