SXA Experience editor throws error - An item with the same key has already been added

Question

I've recently setup SXA. I have a home page where I've added a title and a rich text field. Everything was working nicely until I published my Helix solution to my web folder using the gulp script.

After that, any time I try to edit the Home page using the Experience Editor, I get the following error:

Inner Exception: An item with the same key has already been added.
  at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
  at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
  at Sitecore.Pipelines.GetChromeData.GetPlaceholderChromeData.Process(GetChromeDataArgs args)
  at DynamicPlaceholders.Pipelines.GetChromeData.GetDynamicPlaceholderChromeData.Process(GetChromeDataArgs args)
  at (Object , Object[] )
  at Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args)
  at Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName, PipelineArgs args, String pipelineDomain)
  at Sitecore.Pipelines.GetChromeData.GetChromeDataPipeline.Run(GetChromeDataArgs args)
  at Sitecore.Mvc.ExperienceEditor.Presentation.PlaceholderMarker.GetClientData()
  at Sitecore.Mvc.ExperienceEditor.Presentation.PlaceholderMarker.get_ClientData()
  at Sitecore.Mvc.ExperienceEditor.Presentation.PlaceholderMarker.GetStart()
  at Sitecore.Mvc.ExperienceEditor.Presentation.Wrapper..ctor(TextWriter writer, IMarker marker)
  at Sitecore.Mvc.ExperienceEditor.Pipelines.Response.RenderPlaceholder.AddWrapper.Process(RenderPlaceholderArgs args)
  at (Object , Object[] )
  at Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args)
  at Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName, PipelineArgs args, String pipelineDomain)
  at Sitecore.Mvc.Pipelines.PipelineService.RunPipeline[TArgs](String pipelineName, TArgs args)
  at Sitecore.Mvc.Helpers.SitecoreHelper.Placeholder(String placeholderName)
  at Sitecore.XA.Foundation.SitecoreExtensions.Extensions.RazorExtensions.Placeholder(String placeholderName)
  at ASP._Page_Views_SxaLayout_SxaLayout_cshtml.Execute() in C:\inetpub\wwwroot\XXXXXXX\Views\SxaLayout\SxaLayout.cshtml:line 28
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
  at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
  at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
  at Sitecore.Mvc.Presentation.ViewRenderer.Render(TextWriter writer)

As a fault-finding step, I removed all of the renderings from the presentation details, but that didn't help.

Any ideas what might be causing this?

Answer 1

Thanks Gatogordo.

It turned out that we had some custom dynamic placeholder code. Commenting out the .config that had the pipelines stopped the error. Now I'll have to clean it out completely.