Asp.net 第三级CascadingDropDown未将SelectedValue传递给Ajax调用

我正在尝试使用ASP.NETCascadingDropDown控件呈现用户选择的值和答案。前两个下拉列表始终显示用户上次访问页面时选择的答案。我还可以选择新的值并保存它们，它们会正确地存储在数据库中。问题是下次我来到这个页面编辑下拉值时，前两个正确地显示了用户选择的答案，但第三个没有）

如何使第三个下拉列表正确显示？调试时，所选值似乎没有传递给服务器上的GetTaxo方法

我正在使用中继器输出包含以下内容的自定义控件：

<asp:DropDownList id="cboResponse" DataTextField="lov_label" 
   DataValueField="lov_cd" EnableViewState="True" runat="server" />

<ajaxToolkit:CascadingDropDown ID="CDDL" runat="server" Category="-"
   EnableViewState="True" ServiceMethod="GetTaxo"
   ServicePath="/ajax/SaT.asmx" 
   TargetControlID="cboResponse" PromptValue="-1" PromptText="(Select One)" 
   LoadingText ="Loading..." />

当呈现页面时，我认为设置SelectedValue没有问题。类别为5149的下拉列表，但似乎没有将其SelectedValue传递给服务器：

Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"4548","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_CDDL_ClientState","LoadingText":"Loading...","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_valSelectionRequired'));
}
Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"4025","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_CDDL_ClientState","LoadingText":"Loading...","ParentControlID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_cboResponse","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer2","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_valSelectionRequired'));
}
Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"5149","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_CDDL_ClientState","LoadingText":"Loading...","ParentControlID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_cboResponse","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer3","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_valSelectionRequired'));
}

---

我只是使用ContextKey属性将答案传递给服务器。它复制了knownCategoryValue的用途，但是这个控件很脆弱，我需要完成它，所以我最终使用contextKey来选择正确的答案

Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"4548","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_CDDL_ClientState","LoadingText":"Loading...","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_valSelectionRequired'));
}
Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"4025","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_CDDL_ClientState","LoadingText":"Loading...","ParentControlID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl03_ctl02_cboResponse","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer2","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_valSelectionRequired'));
}
Sys.Application.add_init(function() {
    $create(AjaxControlToolkit.CascadingDropDownBehavior, {"Category":"5149","ClientStateFieldID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_CDDL_ClientState","LoadingText":"Loading...","ParentControlID":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl04_ctl02_cboResponse","PromptText":"(Select One)","PromptValue":"-1","SelectedValue":"MyAnswer3","ServiceMethod":"GetTaxo","ServicePath":"/ajax/SaT.asmx","id":"ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_CDDL"}, null, null, $get("ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_cboResponse"));
});

document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_valSelectionRequired').dispose = function() {
    Array.remove(Page_Validators, document.getElementById('ucInvEdit_ucQuestionRepeater_rptQuestions_ctl05_ctl02_valSelectionRequired'));
}