如何使用DropDownList值分配javascript变量（selection_changed）

Question

我有一个DropDownList将被多次使用，所以我有一个selection_change属性。现在，我试图让用户在列表中选择文件ID。然后我使用他选择的id并运行存储过程。我第一次移动它工作的文件，但第二次（当他选择另一个文件时）它失败了。我的问题是如何将javascript值重新分配给selection_change值？

这是我的职能：

function getCaseFiles(canMoveExpenses) {
        //create Popup with content from div
        $('#ddlFiles').dialog({
            autoOpen: true,
            height: 'auto',
            width: 'auto',
            modal: true,
            buttons: {
                "Ok": function () {
                    //                        var newCaseDdl = document.getElementById("ddlCaseFilesNew");
                    //                        var newCaseDdlInt = newCaseDdl.options[newCaseDdl.selectedIndex].value;
                    var newCaseDdl = ddlCaseFilesNew.options[ddlCaseFilesNew.selectedIndex].value;
                    alert("newCaseDdl = " + newCaseDdl);


                    var oldCaseFile = $("#hidCaseFile").val();
                    alert(oldCaseFile);

                    if (newCaseDdl != -1) {
                        moveCasefile(canMoveExpenses, newCaseDdl, oldCaseFile);
                        $(this).dialog('close');
                    }
                    else {
                        showMessage("Error. Please Select a Value From The Lists.");
                    }
                },
                Cancel: function () {
                    newCaseDdl = null;
                    oldCaseDdl = null;
                    $(this).dialog('close');
                }
            }
        });
    }

我的下拉列表div：

<div id="ddlFiles">
    <label>
        Select new CaseFile:</label>
    <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
        DataTextField="Display" DataValueField="FileID" 
        OnPreRender="ddl_PreRender"  
        Width="300px" />
</div>

下拉列表后面的代码：

if (Request.QueryString["ExpenseID"] != null)
    {
        if (!IsPostBack)
        {
            ddlCaseFilesNew.DataSourceID = "dsCaseFiles";
            ddlCaseFilesNew.SelectedIndex = -1;
            ddlCaseFilesNew.DataTextField = "Display";
            ddlCaseFilesNew.DataValueField = "FileID";
            ddlCaseFilesNew.DataBind();
            ddlCaseFilesNew.Attributes.Add("onchange", "getValue();");
        }
    }