Cant get data from C#, returned one row table data in json?

[WebMethod]

public static GalleryDetailsInPopup[] BindDatatable(int imageId)

{

DataTable dt = new DataTable();

List details = new List();

using (SqlConnection con = new SqlConnection("Server=SERVER1; Database=WomensClothing; uid=sa; pwd=elife@123"))

{

using (SqlCommand cmd = new SqlCommand())

{

cmd.CommandText = "Get_galleryImages";

cmd.CommandType = CommandType.StoredProcedure;

cmd.Parameters.AddWithValue("@imageId", imageId);

cmd.Connection = con;

con.Open();

SqlDataAdapter da = new SqlDataAdapter(cmd);

da.Fill(dt);

foreach (DataRow dtrow in dt.Rows)

{

GalleryDetailsInPopup popupDetails = new GalleryDetailsInPopup();

popupDetails.ImageId = Convert.ToInt32(dtrow["ImageId"].ToString());

popupDetails.OwnerName = dtrow["OwnerName"].ToString();

popupDetails.FrontImage = dtrow["FrontImage"].ToString();

popupDetails.BackImage = dtrow["BackImage"].ToString();

popupDetails.DesignedBy = dtrow["DesignedBy"].ToString();

popupDetails.FrontStyle = dtrow["FrontStyle"].ToString();

popupDetails.BackStyle = dtrow["BackStyle"].ToString();

popupDetails.BodyFabric = dtrow["BodyFabric"].ToString();

popupDetails.SleeveFabric = dtrow["SleeveFabric"].ToString();

popupDetails.YokeFabric = dtrow["YokeFabric"].ToString();

popupDetails.CollerFabric = dtrow["CollerFabric"].ToString();

popupDetails.Price = Convert.ToDouble(dtrow["Price"].ToString());

details.Add(popupDetails);

}

return details.ToArray();

}

$(document).on("click", "[id*=link" + data.d[i].ImageId + "]", function () {

var imageId = $(this).closest("td").find('span').html();

alert(imageId);

$.ajax({

type: "POST",

contentType: "application/json; charset=utf-8",

url: "gallries.aspx/BindDatatable",

data: "{'imageId':'" + imageId + "'}",

dataType: "json",

success: function (popup) {

var frontstyles = popup.ImageId;

alert(frontstyles);

error: function (result) {

alert("Error");

}

});