sharepoint changecontenttype dropdown - sharepoint

Question

SharePoint ChangeContentType DropDown
I have attached an application page to the custom document based content type as its edit form.
That content type is being used in a document library which has more than one content type attached to it.
SharePoint form field controls render the respective fields correctly. Change content type control lists all the content types related to the lists in a dropdown as well. But when I change the selection, means when I select different content type, the form does not show the set of fields for the selected content type rather it stays as it is.
Code:
<%# Assembly Name="$SharePoint.Project.AssemblyFullName$" %>
<%# Import Namespace="Microsoft.SharePoint.ApplicationPages" %>
<%# Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%# Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%# Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>
<%# Import Namespace="Microsoft.SharePoint" %>
<%# Assembly Name="Microsoft.Web.CommandUI, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="ApplicationPage1.aspx.cs" Inherits="DMS_POC.Layouts.DMS_POC.ApplicationPage1" DynamicMasterPageFile="~masterurl/default.master" %>
<%# Register TagPrefix="wssuc" TagName="ToolBar" src="../../../_controltemplates/15/ToolBar.ascx" %>
<asp:Content ID="PageHead" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server">
</asp:Content>
<asp:Content ID="Main" ContentPlaceHolderID="PlaceHolderMain" runat="server">
<table>
<tr>
<td>
<span id='part1'>
<SharePoint:InformationBar ID="InformationBar1" runat="server" />
<div id="listFormToolBarTop">
<wssuc:ToolBar CssClass="ms-formtoolbar" id="toolBarTbltop" RightButtonSeparator="&#160;" runat="server">
<template_rightbuttons>
<SharePoint:NextPageButton ID="NextPageButton1" runat="server"/>
<SharePoint:SaveButton ID="SaveButton1" runat="server"/>
<SharePoint:GoBackButton ID="GoBackButton1" runat="server"/>
</template_rightbuttons>
</wssuc:ToolBar>
</div>
<SharePoint:ItemValidationFailedMessage ID="ItemValidationFailedMessage1" runat="server" />
<table class="ms-formtable" style="margin-top: 8px;" border="0" cellpadding="0" cellspacing="0" width="100%">
<SharePoint:ChangeContentType ID="ChangeContentType1" runat="server" />
<SharePoint:FolderFormFields ID="FolderFormFields1" runat="server" />
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_ProposalNumber" runat="server" FieldName="ProposalNo" />
</td>
<td>
<SharePoint:FormField ID="field_ProposalNumber" runat="server" FieldName="ProposalNo"
ControlMode="Display" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_CustName" runat="server" FieldName="CustomerName" />
</td>
<td>
<SharePoint:FormField ID="field_CustName" runat="server" FieldName="CustomerName"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_ProposalType" runat="server" FieldName="ProposalType" />
</td>
<td>
<SharePoint:FormField ID="field_ProposalType" runat="server" FieldName="ProposalType"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_RevertBy" runat="server" FieldName="RevertBy" />
</td>
<td>
<SharePoint:FormField ID="field_RevertBy" runat="server" FieldName="RevertBy"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td style="vertical-align:top">
<SharePoint:FieldLabel ID="lbl_Details" runat="server" FieldName="Details" />
</td>
<td style="vertical-align:top">
<SharePoint:FormField ID="field_Details" runat="server" FieldName="Details"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_SignRequired" runat="server" FieldName="DigitalSignatureRequired" />
</td>
<td>
<SharePoint:FormField ID="field_SignRequired" runat="server" FieldName="DigitalSignatureRequired"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_Amount" runat="server" FieldName="Amount" />
</td>
<td>
<SharePoint:FormField ID="field_Amount" runat="server" FieldName="Amount"
ControlMode="Edit" />
</td>
</tr>
<tr>
<td colspan="2"> </td>
</tr>
<tr>
<td>
<SharePoint:FieldLabel ID="lbl_Final" runat="server" FieldName="Final" />
</td>
<td>
<SharePoint:FormField ID="field_Final" runat="server" FieldName="Final"
ControlMode="Edit" />
</td>
</tr>
<SharePoint:ApprovalStatus ID="ApprovalStatus1" runat="server" />
<SharePoint:FormComponent ID="FormComponent1" TemplateName="AttachmentRows" ComponentRequiresPostback="false" runat="server" />
</table>
<table cellpadding="0" cellspacing="0" width="100%" style="padding-top: 7px">
<tr>
<td width="100%">
<SharePoint:ItemHiddenVersion ID="ItemHiddenVersion1" runat="server" />
<SharePoint:ParentInformationField ID="ParentInformationField1" runat="server" />
<SharePoint:InitContentType ID="InitContentType1" runat="server" />
<wssuc:ToolBar CssClass="ms-formtoolbar" id="toolBarTbl" RightButtonSeparator="&#160;" runat="server">
<template_buttons>
<SharePoint:CreatedModifiedInfo ID="CreatedModifiedInfo1" runat="server"/>
</template_buttons>
<template_rightbuttons>
<SharePoint:SaveButton ID="SaveButton2" runat="server"/>
<SharePoint:GoBackButton ID="GoBackButton2" runat="server"/>
</template_rightbuttons>
</wssuc:ToolBar>
</td>
</tr>
</table>
</span>
</td>
<td valign="top">
<SharePoint:DelegateControl ID="DelegateControl1" runat="server" ControlId="RelatedItemsPlaceHolder" />
</td>
</tr>
</table>
</asp:Content>
<asp:Content ID="PageTitle" ContentPlaceHolderID="PlaceHolderPageTitle" runat="server">
Application Page
</asp:Content>
<asp:Content ID="PageTitleInTitleArea" ContentPlaceHolderID="PlaceHolderPageTitleInTitleArea" runat="server" >
My Application Page
</asp:Content>

Answer 1

This is an old question but got here while looking for something else.
In case you never found the solution or someone else ends up here here is what you need to do
Add the following in your aspx:
<tr><SharePoint:ListFieldIterator runat="server" ID="ListFieldIterator1" ControlMode="Edit" ExcludeFields="FileLeafRef"/></tr>
This will allow the ChangeContentType control to refresh the fields based on content types. You also don't need all those hard coded form fields as the purpose of the ListFieldIterator is to render the form with the correct controls for you.
Your next problem will probably be to set the values of each control assuming that is what you want to do. For each control type you have to look at the Controls and look for controls like TextBox or DropDownList, etc. Most of the time the control will be deep inside as in something like ((TextBox)control.Controls[1].Controls[0].Control[2]).Text
Not the most elegant way but this is all I could find to make it work.
If you don't need to map values then the first part of my answer is all you need and should be easy to do.
Good luck!