title: Debugging mscorlib in .Net 4.0
body: <p>I'm getting the following exception from System.IO.Path.CheckInvalidPathChars() in mscorlib:</p>
  
  <blockquote>
    <p>[ArgumentException: Illegal characters
    in path.]<br>
    System.IO.Path.CheckInvalidPathChars(String
    path) +142<br>
    System.IO.Path.NormalizePath(String
    path, Boolean fullCheck, Int32
    maxPathLength) +100<br>
    System.IO.Path.GetFullPath(String
    path) +187<br>
    System.Xml.XmlResolver.ResolveUri(Uri
    baseUri, String relativeUri) +114<br>
    System.Xml.XmlTextReaderImpl..ctor(String
    url, XmlNameTable nt) +135<br>
    System.Xml.XmlDocument.Load(String
    filename) +85<br>
    Sitecore.Web.UI.WebControls.WebEditRibbon.ConvertToJson(String
    layout) +210<br>
    Sitecore.Web.UI.WebControls.WebEditRibbon.Render(HtmlTextWriter
    output, Item item) +1268<br>
    Sitecore.Web.UI.WebControl.Render(HtmlTextWriter
    output) +387<br>
    System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter
    writer, ICollection children) +246<br>
    System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter
    writer) +315<br>
    System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter
    writer) +48<br>
    System.Web.UI.Control.RenderControlInternal(HtmlTextWriter
    writer, ControlAdapter adapter)
    +11279890    System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter
    writer, ICollection children) +246<br>
    System.Web.UI.Page.Render(HtmlTextWriter
    writer) +40<br>
    System.Web.UI.Page.ProcessRequestMain(Boolean
    includeStagesBeforeAsyncPoint, Boolean
    includeStagesAfterAsyncPoint) +5274</p>
  </blockquote>
  
  <p>The thing is, I don't what the path value is that's causing this error. It would help if I could debug the method so I can see the value of the path parameter. I enabled stepping into the .Net Framework code in Visual Studio 2010. I've also loaded the related .Net Framework Symbols from the Microsoft Symbol Servers. However, it seems these PDBs don't include the source; so I can't step into CheckInvalidPathChars and retrieve the path value.</p>
  
  <p>Is it possible to debug mscorlib and step through its source?</p>
  
  <p>Relevant info:</p>
  
  <ul>
  <li>.Net Framework 4.0.</li>
  <li>Visual Studio 2010</li>
  </ul>
  
  <p>Any constructive input is greatly appreciated.</p>
  
  <p>Thanks,
  Frank</p>