Creating a custom web.net application that will be hosted in the isv folder

1. Create an empty asp.net website,

2. Add reference to the following assemblies

AntiXssLibrary
Microsoft.Crm
Microsoft.Crm.Platform.Sdk
Microsoft.Crm.Sdk

3. Update web.config enter following details

<?xml version="1.0"?>

<configuration> 

  <system.webServer>

    <validation validateIntegratedModeConfiguration="false"/>

    <modules>

      <remove name="CrmAuthentication"/>

    </modules>

  </system.webServer>

  <system.serviceModel>

    <serviceHostingEnvironment aspNetCompatibilityEnabled="true"/>

  </system.serviceModel>

  <system.web>

    <compilation debug="true">

      <assemblies>

        <add assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System.Runtime.Serialization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Web.ApplicationServices, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

        <add assembly="System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

        <add assembly="System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Xml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Web.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

        <add assembly="System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

        <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.ServiceModel.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System.Data.Services.Client, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Data.Services.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Data.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

        <add assembly="System.Web.DynamicData, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System.ComponentModel.DataAnnotations, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

        <add assembly="System.Web.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

        <add assembly="System.Xml.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

      </assemblies>

    </compilation>

  </system.web> 

</configuration>

4. To reference fields on the crm entity form use
add a following line in the head tag of aspx/html page

<script type="text/javascript" src="/<crm org name>/webresources/clientglobalcontext.js.aspx"></script>

and then to reference the field on the entity form

<script type="text/javascript">
window.top.opener.Xrm.Page.data.entity.attributes.get("prefix_attributename").setValue("some value")
</script>