Uncaught SyntaxError: Unexpected token < in JSON with ASP.Net WebMethod

Question

I'm running into a problem with implementing a jQuery bootgrid into my ASP.Net Webforms application.

I get the following problem on my page load which prevents the bootgrid from loading data:

Uncaught SyntaxError: Unexpected token < in JSON at position 4

    at Function.parse [as parseJSON] ()

        at Object.success (jquery.bootgrid.js:232)

        at fire (jquery-3.1.1.js:3305)

        at Object.fireWith [as resolveWith] (jquery-3.1.1.js:3435)

        at done (jquery-3.1.1.js:9242)

        at XMLHttpRequest.

This is my bootgrid implementation in the JavaScript:

$("#grid").bootgrid({
    ajax: true,
    url: "/Secure/Maintenance/Roles.aspx/GetData",
    rowCount: [10, 50, 75, 100, 200, -1]
})

And then here is my C# WebMethod:

[WebMethod]
public static string GetData()
{
    var results = (from x in EFDB.AspNetRoles
                   select x).AsQueryable();

    return JsonConvert.SerializeObject(results);
}

I've used a LINQ Query to get the data and tried converting it to JSON but I'm not sure if I'm doing it correctly. When I set breakpoints in the GetData method, none of them get reached. So I'm really having trouble debugging this.

Any advice on what I could be doing wrong?

Thanks!

Answer 1

I ended up creating an Generic Handler to post the data and that worked well. Here's is the full code for the Generic Handler:

public class RolesHandler : IHttpHandler
{

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/json";
        context.Response.Write(GetData());
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

    public string GetData()
    {
        var result = string.Empty;
        var con = new SqlConnection();
        var cmd = new SqlCommand();
        var dt = new DataTable();
        string sSQL = @"SELECT Id, Name
                        FROM dbo.AspNetRoles;";

        try
        {
            using (var connection = THF.Models.SQLConnectionManager.GetConnection())
            {
                using (var command = new SqlCommand(sSQL, connection))
                {
                    connection.Open();
                    command.CommandTimeout = 0;
                    var da = new SqlDataAdapter(command);
                    da.Fill(dt);
                }
            }

            var sNumRows = dt.Rows.Count.ToString();
            var sDT = JsonConvert.SerializeObject(dt);
            result = "{ \"current\": 1, \"rowCount\": 10, \"rows\": " + sDT + ", \"total\": " + sNumRows + " }";
        }
        catch (Exception ex)
        {
        }
        finally
        {
            cmd.Dispose();
            THF.Models.SQLConnectionManager.CloseConn(con);
        }

        return result;
    }