jQuery结合AJAX之在页面滚动时从服务器加载数据

public static string  GetDataFromServer()
{
    string resp = string.Empty;
    for(int i = 0; i <= 10; i++)
    {
        resp += "<p><span>"  + counter++ +
          "</span> This content is dynamically appended " +
          "to the existing content on scrolling.</p>" ;
    }
    return resp;
}

public static string GetDataFromServer()
    {
        DataSet ds = new DataSet();
 
        // Set value of connection string here
        string strConnectionString = ""; // Insert your connection string value here
        SqlConnection con = new SqlConnection(strConnectionString);
 
        // Write the select command value as first parameter
        SqlCommand command = new SqlCommand("SELECT * FROM Person", con);
        SqlDataAdapter adp = new SqlDataAdapter(command);
int retVal = adp.Fill(ds);
 
        string resp = string.Empty;
for (int i = 1; i <= ds.Tables[0].Rows.Count; i++)
        {
            string strComment = string.Empty;
if (ds.Tables != null)
            {
if (ds.Tables[0] != null)
                {
if (ds.Tables[0].Rows.Count > 0)
                    {
if (ds.Tables[0].Rows.Count >= i - 1)
                        {
if (ds.Tables[0].Rows[i - 1][0] != DBNull.Value)
                            {
                                strComment = ds.Tables[0].Rows[i - 1][0].ToString();
                            }
                        }
                    }
                }
            }
            resp += "<p><span>" + counter++ + "</span> " + strComment + "</p>";
        }
return resp;
    }

$(document).ready(function(){$contentLoadTriggered = false;$("#mainDiv").scroll(function(){if($("#mainDiv").scrollTop() >= ($("#wrapperDiv").height() -  $("#mainDiv").height()) &&  $contentLoadTriggered == false)  $contentLoadTriggered == false){$contentLoadTriggered = true;$.ajax({type: "POST",url: "LoadOnScroll.aspx/GetDataFromServer",data: "{}",contentType: "application/json; charset=utf-8",dataType: "json",async: true,cache: false,success: function (msg){$("#wrapperDiv").append(msg.d);$contentLoadTriggered = false;},error: function (x, e){alert("The call to the server side failed. " +x.responseText);}});}});});

if($("#mainDiv").scrollTop() >= ($("#wrapperDiv").height() - $("#mainDiv").height()) &&  $contentLoadTriggered == false)

success: function (msg){$("#wrapperDiv").append(msg.d);$contentLoadTriggered = false;}