If you are trying to host the blogengine site within a virtual directory of the Umbraco site, then you will have to amend the blogengine web.config to "remove" all the Umbraco-specific handlers and modules, as these will be inherited by the blogengine application, causing this exception because the application can't find the relevant DLLs in its bin folder.
I recently had a similar problem and I have posted the web.config I used in the virtual directory below. Mine was a very simple web application, so obviously this will not work by itself in your blogengine app. You will need to add the relevant parts into your web.config file.
Also, this was for a v6 Umbraco install in IIS7.5, so you may have to experiment a little.
<?xml version="1.0"?>
<configuration>
<configSections>
<remove name="urlrewritingnet" />
<remove name="umbraco.presentation.Properties.Settings" />
<remove name="clientDependency" />
<remove name="Examine" />
<remove name="ExamineLuceneIndexSets" />
<remove name="FileSystemProviders" />
<remove name="log4net" />
<remove name="BaseRestExtensions" />
<remove name="system.web.webPages.razor" />
</configSections>
<appSettings>
<clear/>
</appSettings>
<system.web>
<httpModules>
<remove name="UrlRewriteModule" />
<remove name="UmbracoModule" />
<remove name="ClientDependencyModule" />
</httpModules>
<httpHandlers>
<remove verb="*" path="umbraco/channels.aspx" />
<remove verb="*" path="umbraco/channels/word.aspx" />
<remove verb="*" path="DependencyHandler.axd" />
<remove verb="GET,HEAD,POST" path="GoogleSpellChecker.ashx" />
</httpHandlers>
<compilation defaultLanguage="c#" debug="false" batch="false" targetFramework="4.0">
<buildProviders>
<remove extension=".cshtml" />
<remove extension=".vbhtml" />
<remove extension=".razor" />
</buildProviders>
</compilation>
<membership>
<providers>
<remove name="UmbracoMembershipProvider" />
<remove name="UsersMembershipProvider" />
</providers>
</membership>
<!-- added by NH to support membership providers in access layer -->
<roleManager enabled="false">
<providers>
<remove name="UmbracoRoleProvider" />
</providers>
</roleManager>
<!-- Sitemap provider-->
<siteMap defaultProvider="UmbracoSiteMapProvider" enabled="false">
<providers>
<remove name="UmbracoSiteMapProvider" />
</providers>
</siteMap>
</system.web>
<system.webServer>
<modules>
<remove name="UrlRewriteModule" />
<remove name="UmbracoModule" />
<remove name="ClientDependencyModule" />
</modules>
<handlers accessPolicy="Read, Write, Script, Execute">
<remove name="Channels" />
<remove name="Channels_Word" />
<remove name="ClientDependency" />
<remove name="SpellChecker" />
</handlers>
</system.webServer>
</configuration>
Update:
It may also be necessary to update the <system.web.webPages.razor>
section if this is present in your application web.config, changing the host
and pages
entries back to their defaults:
<host factoryType="System.Web.WebPages.Razor.WebRazorHostFactory,
System.Web.WebPages.Razor" />
<pages pageBaseType="System.Web.WebPages.WebPage">
This is because Umbraco implements it's own hostfactory and page base.