Content cleaner. A Episerver admin mode plugin to let you find content of a specific type and delete all or selected instances

Cleaner.aspx

<%@ Page Language="c#" CodeBehind="Cleaner.aspx.cs" AutoEventWireup="False" Inherits="LatestEpi.modules.TypeContentCleaner.Cleaner" Title="" %>

<%@ Import Namespace="EPiServer.Web.Mvc.Html" %>

<asp:content contentplaceholderid="MainRegion" runat="server">

    <asp:HiddenField runat="server" id="SelectedScheduledJobGUID" ClientIDMode="static" />   
    <asp:HiddenField runat="server" id="SelectedMedia" ClientIDMode="static" />

    <script type="text/javascript">

        function SetCheckBoxes(getAll) {
            var checkboxValues = [];

            if (getAll) {
                $('input[type="checkbox"]').map(function () {
                    checkboxValues.push($(this).val());
                });
            }
            else {
                $('input:checked').map(function () {
                    checkboxValues.push($(this).val());
                });
            }

            $('#SelectedMedia').val(checkboxValues.join(','));

            //console.log(checkboxValues);
        };

        function SetSelected() {
            $('#SelectedScheduledJobGUID').val($('#TypeID').val());
            ///console.log($('#TypeID option:selected').text());
        }

    </script>

    <div class="epi-formArea epi-paddingHorizontal">
        <fieldset>   
             <legend>Select content type</legend>  
                <asp:Repeater id="rptTypes" runat="server">
                    <HeaderTemplate>
                        <select id="TypeID">
                    </HeaderTemplate>
                    <ItemTemplate>
                        <option value="<%#CType.ID %>"><%#CType.Name %></option>
                    </ItemTemplate>
                    <FooterTemplate>
                        </select>
                    </FooterTemplate>
             </asp:Repeater>    

            <div class="epi-buttonContainer epi-marginVertical">
                <span class="epi-cmsButton">
                    <asp:Button  OnClientClick="SetSelected()" ClientIDMode="Static" Text="List content" CssClass="epi-cmsButton-text epi-cmsButton-tools epi-cmsButton-Save" id="btnList" onmouseover="EPi.ToolButton.MouseDownHandler(this)" onmouseout="EPi.ToolButton.ResetMouseDownHandler(this)" runat="server" />
                </span>
             </div>

        </fieldset>

         <div class="epi-buttonContainer">
            <span class="epi-cmsButton">
                <asp:Button  OnClientClick="SetCheckBoxes(1)" ClientIDMode="Static" Text="Delete all" CssClass="epi-cmsButton-text epi-cmsButton-tools epi-cmsButton-Save" id="btnDeleteAll" onmouseover="EPi.ToolButton.MouseDownHandler(this)" onmouseout="EPi.ToolButton.ResetMouseDownHandler(this)" runat="server" />
                </span>
            <span class="epi-cmsButton">
                <asp:Button  OnClientClick="SetCheckBoxes(0)" ClientIDMode="Static" Text="Delete selected" CssClass="epi-cmsButton-text epi-cmsButton-tools epi-cmsButton-Save" id="btnDeleteSelected" onmouseover="EPi.ToolButton.MouseDownHandler(this)" onmouseout="EPi.ToolButton.ResetMouseDownHandler(this)" runat="server" />
            </span>
        </div>
        <div class="epi-buttonContainer"></div>

        <fieldset>   
             <legend>Content</legend>  
              <dl>             
                  <dd>
                      <asp:Repeater runat="server" id="rptContentUsage">
                          <ItemTemplate>
                              <div class="epi-size25">
                                  <input type="checkbox" value="<%#CUsage.ContentLink %>" /> <label><a href="<%#Url.ContentUrl(CUsage.ContentLink) %>" target="_blank"><%# BreadCrumb(CUsage.ContentLink)%></a></label>
                              </div>   
                          </ItemTemplate>
                      </asp:Repeater>
                   
                      <asp:Literal runat="server" id="Literal4" />
                  </dd>
              </dl>   
     
        </fieldset>

    </div>


  </asp:content>

Cleaner.aspx.cs

using System;
using System.Collections.Generic;
using System.Web.Security;
using System.Web.UI.WebControls;
using EPiServer.Personalization;
using EPiServer.PlugIn;
using EPiServer.Security;
using EPiServer.Util.PlugIns;
using System.Web.UI;
using EPiServer.Shell.WebForms;
using EPiServer;
using EPiServer.Core;
using EPiServer.ServiceLocation;
using System.Linq;
using System.Web.Mvc;
using EPiServer.DataAbstraction;

namespace LatestEpi.modules.TypeContentCleaner
{
    [GuiPlugIn(DisplayName = "Content cleaner", Description = "", Area = PlugInArea.AdminMenu, Url = "~/modules/TypeContentCleaner/Cleaner.aspx")]
    public partial class Cleaner : WebFormsBase
    {
        private IContentRepository contentRepository = ServiceLocator.Current.GetInstance<IContentRepository>();
        protected UrlHelper Url = ServiceLocator.Current.GetInstance<UrlHelper>();
        protected ContentType CType{ get { return Page.GetDataItem() as ContentType; } }
        protected ContentUsage CUsage { get { return Page.GetDataItem() as ContentUsage; } }

        protected override void OnPreInit(EventArgs e)
        {
            base.OnPreInit(e);

            MasterPageFile = UriSupport.ResolveUrlFromUIBySettings("MasterPages/EPiServerUI.master");
            SystemMessageContainer.Heading = "Content Cleaner";
            SystemMessageContainer.Description = "A plugin that fgets all content for a type and let you delete all or selected.";
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            btnList.Click += BtnList_Click;
            btnDeleteAll.Click += BtnbtnDelete_Click;
            btnDeleteSelected.Click += BtnbtnDelete_Click;
        }


        protected override void OnLoad(EventArgs e)
        {
            rptTypes.DataSource = ServiceLocator.Current.GetInstance<IContentTypeRepository>().List().OrderBy(p => p.Name); ;
            rptTypes.DataBind();

        }

        protected string BreadCrumb(ContentReference cReference)
        {
            var ancestor = contentRepository.GetAncestors(cReference).ToList();
            var content = contentRepository.Get<IContent>(cReference);

            string path = "";

            for (int x = ancestor.Count() - 1; x >= 0; x--)
            {
                path += "\\" + ancestor[x].Name;
            }

            return (path + "\\" + content.Name).Trim("\\".ToCharArray());
        }

        protected string UiUrl()
        {
            return EPiServer.Configuration.Settings.Instance.UIUrl.ToString().Trim('~');
        }

        private void BtnList_Click(object sender, EventArgs e)
        {
            var contentModelUsage = ServiceLocator.Current.GetInstance<IContentModelUsage>();
            var contentRepository = ServiceLocator.Current.GetInstance<IContentRepository>();
            var selectedTypeID = SelectedScheduledJobGUID.Value;

            var contentType = ServiceLocator.Current.GetInstance<IContentTypeRepository>().Load(Int32.Parse(selectedTypeID));
            var usages = contentModelUsage.ListContentOfContentType(contentType).OrderBy(x => x.Name);

            rptContentUsage.DataSource = usages;
            rptContentUsage.DataBind();
        }

        private void BtnbtnDelete_Click(object sender, EventArgs e)
        {
            var selectedContentLinks = SelectedMedia.Value.Split(",".ToCharArray());

            foreach (var contentLink in selectedContentLinks)
            {
                contentRepository.Delete(ContentReference.Parse(contentLink), false, AccessLevel.NoAccess);
            }
        }

    }
}

Cleaner.aspx.designer.cs

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated. 
// </auto-generated>
//------------------------------------------------------------------------------

namespace LatestEpi.modules.TypeContentCleaner {
    
    
    public partial class Cleaner {
        
        /// <summary>
        /// SelectedScheduledJobGUID control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.HiddenField SelectedScheduledJobGUID;
        
        /// <summary>
        /// SelectedMedia control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.HiddenField SelectedMedia;
        
        /// <summary>
        /// rptTypes control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Repeater rptTypes;
        
        /// <summary>
        /// btnList control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btnList;
        
        /// <summary>
        /// btnDeleteAll control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btnDeleteAll;
        
        /// <summary>
        /// btnDeleteSelected control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btnDeleteSelected;
        
        /// <summary>
        /// rptContentUsage control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Repeater rptContentUsage;
        
        /// <summary>
        /// Literal4 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Literal Literal4;
    }
}

Based on this nice solution from @PNergard, I have created something similar for Optimizely CMS 12:
Content Cleaner Tool for Optimizely CMS 12