FormBuilder code suggestions for POCO
Your naming conventions are a bit off. Property names (i.e. in FormClass) are commonly PascalCase.
If you are not married to the XML file structure (i.e. it's under your control) then you can simplify the de/serialization quite a lot by using the XmlSerializer. For example:

public class ClassDetails
{
    public List&lt;FormClass&gt; Models { get; set; }
}

public static class XmlUtils
{

    public static void Save&lt;T&gt;(T obj, string filename, string namespace)
    {
         using (var writer = new StreamWriter(filename))
         {
             var serializer = new XmlSerializer(typeof(T), namespace);
             serializer.Serialize(writer, obj);
         }
    }

    public static T Load&lt;T&gt;(string filename, string namespace)
    {
         using (var writer = new StreamWriter(filename))
         {
             var serializer = new XmlSerializer(typeof(T), namespace);
             return (T)serializer.Deserialize(writer);
         }
    }
}


then you can load/save the file with:

var details = XmlUtils.Load&lt;ClassDetails&gt;(@"c:\form.xml", "http://CompanyName.AppName.Service.Contracts");

...

XmlUtils.Save(details, @"c:\form.xml", "http://CompanyName.AppName.Service.Contracts");

Rather than having a big if-else cascade I'd use a dictionary to map the types:

Dictionary&lt;string, string&gt; ModelToFormTypeMap = 
    new Dictionary&lt;string, string&gt; {
          { "System.String", "TextBox" },
          { "System.Enum", "DropDown" },
          ...
        };


then with an addition of a little bit of Linq you get 

XmlUtils.Load&lt;ClassDetails&gt;((@"c:\form.xml", "http://CompanyName.AppName.Service.Contracts")
        .Models
        .Select(m =&gt; new FormStructure 
                     {
                          FormStructureId = newGuid,
                          name = m.name,
                          displayname = m.displayName,
                          FormKey = m.key,
                          Required = m.required,
                          ClassName = "Incident",
                          ControlType = ModelToFormTypeMap[m.type]
                     })
         .ToList();