bind textbox like dropdownlist

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C#

ASP.NET

Can I bind textbox like dropdownlist means in dropdownlist we can set datatextfield to show text and datavaluefield to insert value into database.

I have to do using textbox,I have added Autocomplete ajax toolkit extender to textbox. I am showing only Student Names but on click of button i have to insert SID of student not student name into the database.I search google they tell me use OnClientItemSelected of Autocomplete extender.How can i do any idea regarding this.

[System.Web.Services.WebMethodAttribute(), System.Web.Script.Services.ScriptMethodAttribute()]
        public static string[] Getdata(string prefixText, int count, string contextKey)
        {
            strSQL = "SELECT SID,Student_Name FROM Student_Master WHERE Student_Name Like '" + prefixText + "%'";
            DataTable dataTablePatient_Master = null;
            dataTablePatient_Master = objSqlDbComm.ExecuteDatasetQuery(strSQL).Tables[0];

            List<String> list = new List<String>();
            foreach(DataRow dr in dataTablePatient_Master.Rows)
            {
                list.Add(dr["Student_Name"].ToString());

            }
            return list.ToArray();
        }

<asp:TextBox ID="txtStudentName" AutoCompleteType="Disabled" CssClass="csstextbox"
                                    runat="server"></asp:TextBox>
                                <asp:AutoCompleteExtender ID="txtStudentName_AutoCompleteExtender" runat="server"
                                    ServiceMethod="Getdata" OnClientItemSelected="OnItemSelected" CompletionListCssClass="cssautocompletetextbox" MinimumPrefixLength="1"
                                    CompletionInterval="1000" EnableCaching="true" CompletionSetCount="1" TargetControlID="txtStudentName"
                                    UseContextKey="True">
                                </asp:AutoCompleteExtender>