Sitecore Multisite 404, 500 & Robots.txt

error-code.cs

HttpContext.Current.Response.StatusCode = 404;

exclusion-rules.config

<add type="Contains" match="~/media/" />
<add type="Contains" match="~/icon/" />
<add type="Contains" match="~/link.aspx" />
<add type="StartsWith" match="/sitecore" />
<add type="Contains" match=".asmx" />
<add type="Contains" match=".ashx" />

global.asax.cs

public void Application_Error(object sender, EventArgs args)
{
    Sitecore.MultisiteHttpModule.Errors.ErrorHandler.HandleError(Server.GetLastError());
}

nuget

PM> Install-Package Sitecore.MultisiteHttpModule

Pipeline-httpRequestBegin.config

<httpRequestBegin>
    <processor type="Sitecore.MultisiteHttpModule.NotFound.NotFoundHandler, Sitecore.MultisiteHttpModule" patch:after="processor[@type='Sitecore.Pipelines.HttpRequest.ItemResolver, Sitecore.Kernel']" />
</httpRequestBegin>

sites-node.config

<site name="MySite" 
      ...
      notFoundPageId="{BFA65433-4552-4507-9375-C96137287640}"
      errorPagePath="/errors/MySite.html" 
      robotsTxtLocation="/robots/MySite.robots.txt" />

web.config

<configSections>
    <section name="multisiteHttpModule" type="Sitecore.MultisiteHttpModule.Configuration.MultisiteHttpModuleSettings, Sitecore.MultisiteHttpModule" />
</configSections>

<multisiteHttpModule defaultErrorPage="/error.html" errorsEnabled="True" notFoundEnabled="True">
    <exclude404Rules>
        <add type="Contains" match="~/media/" />
        <add type="Contains" match="~/icon/" />
        <add type="Contains" match="~/link.aspx" />
        <add type="StartsWith" match="/sitecore" />
        <add type="Contains" match=".asmx" />
        <add type="Contains" match=".ashx" />
    </exclude404Rules>
</multisiteHttpModule>

<system.webServer>
    <handlers>
        <add name="RobotsHandler" path="/robots.txt" verb="GET" type="Sitecore.MultisiteHttpModule.Robots.RobotsHandler, Sitecore.MultisiteHttpModule" />
    </handlers>
</system.webServer>