How to bind checkboxlist on textbox onchange event using javascript

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i have a textbox inside a gridview. i call a javascipt function on textbox onclick event. and need to bind a checkboxlist using this javascript function.

here is my code:-

<asp:GridView ID="GridView2" runat="server" C AutoGenerateColumns="False" Width="100%">
    <Columns>
        <asp:TemplateField HeaderText="text1" >
            <ItemTemplate>
                <asp:TextBox ID="txt1" runat="server" onclick='<%#string.Format("javascript:BindCheckboxlist(\"{0}\", \"{1}\")", ((GridViewRow) Container).FindControl("txt1").ClientID, ((GridViewRow) Container).FindControl("txt2").ClientID) %>' Text='<%# Bind("txt1") %>'></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="text2" >
            <ItemTemplate>
                <asp:TextBox ID="txt2" runat="server" Text='<%# Bind("txt2") %>'></asp:TextBox>
            </ItemTemplate>
            <ControlStyle Width="150px" />
        </asp:TemplateField>
    </Columns>
</asp:GridView>

<asp:CheckBoxList ID="chklist" runat="server">
  </asp:CheckBoxList>

i am getting error

Cannot read property 'getElementsByTagName' of null

.
can someone suggest me this solution. how can i do it this.

What I have tried:

<script type="text/javascript">
            function BindCheckboxlist(_txt1, _txt2) {

                var CHK = document.getElementById("<%=chklist.ClientID%>");

                    addToCheckBoxListList(CHK,'abc','abc')
            }

            function addToCheckBoxListList(checkBoxListId, displayText, checkBoxValue) {
                var checkBoxListRef = document.getElementById(checkBoxListId);
                var rowArray = checkBoxListRef.getElementsByTagName('input');
                var rowCount = rowArray.length;

                var rowElement = checkBoxListRef.insertRow(rowCount);
                var columnElement = rowElement.insertCell(0);

                var checkBoxRef = document.createElement('input');
                var labelRef = document.createElement('label');

                checkBoxRef.type = 'checkbox';
                checkBoxRef.value = checkBoxValue;
                checkBoxRef.id = checkBoxListId + '_' + rowCount;
                checkBoxRef.name = checkBoxListId + ':' + rowCount;

                labelRef.innerHTML = displayText;

                columnElement.appendChild(checkBoxRef);
                columnElement.appendChild(labelRef);
            }
    </script>

Posted 13-Jun-20 3:51am

TCS54321

Updated 15-Jun-20 8:54am

v2

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Richard Deeming · Answer 1 · 2020-06-15T08:55:00

Start by passing the ID of the checkbox list to the addToCheckBoxListList function, rather than passing the element itself:

JavaScript

function BindCheckboxlist(_txt1, _txt2) {
    var CHK = "<%=chklist.ClientID%>";
    addToCheckBoxListList(CHK, 'abc', 'abc');
}

You'll need to check whether the control actually renders a surrouding element. If it doesn't, document.getElementById won't find anything.

Also, the server-side control won't know anything about the values you've added via Javascript. You'll have to read the Request.Form collection to read the values from them.