The core issue here is that you're trying to mix client-side JavaScript-generated HTML with a runat="server" attribute, which is processed by ASP.NET on the server before your JavaScript ever runs. ASP.NET tries to parse all runat="server" tags during page rendering, but since your id value is dynamically generated in JavaScript (not known at server-render time), it can't resolve the server tag correctly—hence the "server tag is not well formed" error.

Let's break down the fixes based on whether you actually need server-side access to this <tbody> element:

Fix 1: Remove runat="server" (If You Don't Need Server-Side Access) #

If you don't need to interact with this <tbody> from your server-side code (like C#/VB.NET), simply remove the runat="server" attribute. This eliminates the ASP.NET parsing conflict entirely.

Modified code:

var HTMLStr, newtbl = tbl + "Table";
HTMLStr = '<tbody id="' + newtbl + '" class="prodTbl"><tr>';

Just make sure newtbl contains a valid HTML ID (no spaces, special characters other than -, _, :, or .). If tbl might have invalid characters, sanitize it first:

// Sanitize the ID to remove invalid characters
var sanitizedTbl = tbl.replace(/[^a-zA-Z0-9\-_:.]/g, '');
var newtbl = sanitizedTbl + "Table";
HTMLStr = '<tbody id="' + newtbl + '" class="prodTbl"><tr>';

Fix 2: Generate the Element Server-Side (If You Need Server-Side Access) #

If you do need to access this <tbody> from server-side code, you should create it in your code-behind instead of client-side JavaScript. This lets ASP.NET properly handle the runat="server" tag and dynamic ID.

Example in C# (code-behind):

// Assuming "tbl" is a server-side variable (adjust as needed)
string newtbl = tbl + "Table";
HtmlGenericControl tbody = new HtmlGenericControl("tbody");
tbody.ID = newtbl;
tbody.Attributes.Add("class", "prodTbl");
tbody.Runat = "server";

// Add a <tr> to the tbody (example)
HtmlGenericControl tr = new HtmlGenericControl("tr");
tbody.Controls.Add(tr);

// Add the tbody to your table (replace "yourTableID" with your actual table's server ID)
yourTableID.Controls.Add(tbody);

This way, ASP.NET generates the correct server-side control with the dynamic ID, and you won't get parsing errors.

Why the "Is not a valid identifier" Error Happens #

This usually means newtbl contains characters that aren't allowed in an HTML ID or an ASP.NET server control ID. Server control IDs have stricter rules (no spaces, special characters like @, #, etc.). Sanitizing the ID as shown in Fix 1 will resolve this.

内容的提问来源于stack exchange，提问作者Edward H