Kendo dropdownlist produces TypeError: n.slice is not a function

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MVC

Kendo

Do I need to define the schema? If so, what should that look like? My searches for this seem to only turn up js solutions, I'm looking for the syntax to define it in the editortemplate.

Shared/editortemplate:

@(
Html.Kendo().DropDownList()
.Name("SearchFunction")
.DataTextField("SearchFunctionDesc")
.DataValueField("SearchFunctionCode")
.DataSource(source =>
    {        
        source.Read(read => { 
            read.Action("GetSearchFunctions", "User");
        });
    })
    .OptionLabel("--Select a Search Function--")
    .AutoBind(false)
)

In the user controller:

public JsonResult GetSearchFunctions([DataSourceRequest] DataSourceRequest request)
{
    var searchFuncs = cmsViewAdminService.GetSearchFunctions();
    DataSourceResult result = searchFuncs.ToDataSourceResult(request);
    return Json(result, JsonRequestBehavior.AllowGet);
}

And then my Dapper db query:

var result = new List<SearchFunction>();
using (var conn = new OracleConnection(DatabaseConnectionString))
{
    conn.Open();
    string query = "select FUNCTION_ID, SEARCH_FUNCTION_CD, " +
            "SEARCH_FUNCTION_DESC, IS_ACTIVE " +
             "from TBL_SEARCH_FUNCTIONS ";
    result = conn.Query(query)
        .Select(s => new SearchFunction
        {
            FunctionId = (int)s.FUNCTION_ID,
            SearchFunctionCode = s.SEARCH_FUNCTION_CD,
            SearchFunctionDesc = s.SEARCH_FUNCTION_DESC,
            Active = s.IS_ACTIVE
        }).ToList<SearchFunction>();
    conn.Close();
    return result;
}