Working on view with two forms on one controller in mvc 5 - asp.net-mvc

Question

I have one drop down box. Based on the selected item of dropdownbox i want to generate form below on same view, Please find the code below.
[HttpGet]
public ActionResult BindDropDown()
{
ViewBag.doctype = new SelectList(db.DocTypeMasters, "Id", "DocTypeName");
return View();
}
[HttpPost]
public ActionResult BindDropDown(string DocType)
{
String Doc = DocType.Trim();
return View();
}
this is my view code
#model C3CardKYC.Models.DocTypeMaster
#{
ViewBag.Title = "BindDropDown";
}
<h2>BindDropDown</h2>
<script src="http://code.jquery.com/jquery-1.9.1.js" type="text/javascript"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {
$('#MyIdAndName').change(function () {
var DocType = $("#MyIdAndName option:selected").text();
alert(DocType);
$.ajax({
url: '#Url.Action("BindDropDown", "Document")',
type: 'POST',
data: { DocType: DocType },
success: function (result) {
alert('success')
}
})
});
});
</script>
<fieldset>
<legend>DocTypeMaster</legend>
#*Select Document Type: #Html.DropDownList("doctype", "Select");*#
#Html.DropDownList("MyIdAndName", ViewBag.doctype as SelectList, " -- Select Document Type -- ")
</fieldset>
<p id="hi">
#Html.ActionLink("Back to List", "Index")
</p>
<div id="hi">
#using (Html.BeginForm("BindDropDown", "Document", FormMethod.Post, new { id = "submitForm" }))
{
<fieldset>
<ol>
<li>
#Html.LabelFor(Model => Model.DocTypeName)
#Html.TextBoxFor(Model => Model.DocTypeName, new { maxlength = 50 })
#Html.ValidationMessageFor(Model => Model.DocTypeName)
</li>
</ol> <button type="submit" id="btnSave" name="Command" value="Save">Save</button>
<button type="submit" id="btnSubmit" name="Command" value="Submit">Submit</button>
<button type="submit" id="btnCancel" name="Command" value="Cancel" onclick="$('#submitForm').submit()">Cancel (Server Side)</button>
</fieldset>
}
</div>
When i run this below error is coming.
There is no ViewData item of type 'IEnumerable' that has the key 'MyIdAndName'.
and if i select the item frm dropdown then only below form should appear. Please suggest